Invasive alien species in Switzerland - Schweizer ...

29 

06 

> Environmental studies 

> Organisms 

> Invasive alien species 

in Switzerland 

An inventory of alien species and their threat to biodiversity 

and economy in Switzerland 

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Environmental studies > Organisms 

> 

Invasive alien species 


An inventory of alien species and their threat to biodiversity 

and economy in Switzerland 

Mit deutscher Zusammenfassung – Avec résumé en français 

Published by the Federal Office for the Environment FOEN 

Bern, 2006

Impressum 

Editor 

Federal Office for the Environment (FOEN) 

FOEN is an office of the Federal Department of Environment, 

Transport, Energy and Communications (DETEC). 

Authors 

Rüdiger Wittenberg, CABI Bioscience Switzerland Centre, 

CH–2800 Delémont 

Marc Kenis, CABI Bioscience Switzerland Centre, CH–2800 Delémont 

Theo Blick, D–95503 Hummeltal 

Ambros Hänggi, Naturhistorisches Museum, CH–4001 Basel 

André Gassmann, CABI Bioscience Switzerland Centre, 

CH–2800 Delémont 

Ewald Weber, Geobotanical Institute, Swiss Federal Institute of 

Technology, CH–8044 Zürich 

FOEN consultant 

Hans Hosbach, Head of Section, Section Biotechnology 

Suggested form of citation 

Wittenberg, R. (ed.) (2005) An inventory of alien species and their 

threat to biodiversity and economy in Switzerland. CABI Bioscience 

Switzerland Centre report to the Swiss Agency for Environment, 

Forests and Landscape. The environment in practice no. 0629. 

Federal Office for the Environment, Bern. 155 pp. 

Design 

Ursula Nöthiger-Koch, 4813 Uerkheim 

Fact sheets 

The fact sheets are available at 

www.environment-switzerland.ch/uw-0629-e 

Pictures 

Cover picture: 

Harmonia axyridis 

Photo Marc Kenis, CABI Bioscience, Delémont. 

Orders 

FOEN 

Documentation 

CH-3003 Bern 

Fax +41 (0)31 324 02 16 

docu@bafu.admin.ch 

www.environment-switzerland.ch/uw-0629-e 

Order number and price: 

UW-0629-E / CHF 20.– (incl. VAT) 

© FOEN 2006

Table of contents 3 

Table of contents 

Abstracts 5 

Vorwort 7 

Summary 8 

Zusammenfassung 12 

Résumé 17 

1 Introduction 22 

1.1 Definitions 23 

1.2 Invasive alien species – a global overview 24 

1.3 Status of alien species in Switzerland 28 

1.4 Pathways 28 

1.5 Impacts of invasive alien species 29 

1.6 Discussion 31 

1.7 Recommendations 32 

1.8 Acknowledgements 34 

2 Vertebrates – Vertebrata 36 

2.1 Mammals – Mammalia 36 

2.2 Birds – Aves 44 

2.3 Reptiles – Reptilia 52 

2.4 Amphibians – Amphibia 54 

2.5 Fish – Pisces 55 

3 Crustaceans – Crustacea 65 

4 Insects – Insecta 71 

4.1 Introduction 71 

4.2 Coleoptera 73 

4.3 Lepidoptera 75 

4.4 Hymenoptera 77 

4.5 Diptera 79 

4.6 Hemiptera 80 

4.7 Orthoptera 82 

4.8 Dictyoptera 83 

4.9 Isoptera 83 

4.10 Thysanoptera 83 

4.11 Psocoptera 84 

4.12 Ectoparasites 84 

5 Spiders and Allies – Arachnida 101 

5.1 Introduction 101 

5.2 List of species 102 

5.3 Species of natural habitats 103 

5.4 Species in, and in close proximity to, 

human buildings 106 

5.5 Greenhouse-inhabiting species 108 

5.6 «Banana spiders» and terrarium species 109 

5.7 Discussion and recommendations 109 

6 Molluscs – Mollusca 113 

6.1 Snails and slugs (Gastropoda) 113 

6.2 Bivalves (Bivalvia) 115 

7 Other selected invertebrate groups 121 

7.1 Nematodes – Nemathelminthes 121 

7.2 Flatworms – Turbellaria, Plathelminthes 122 

7.3 Segmented worms – Annelida 122 

7.4 Centipedes and millipedes – Myriapoda 123 

8 Lichens (Lichen-forming fungi) 124 

9 Fungi and a selected bacterium 125 

10 Plants – Planta 128 

10.1 Introduction and terminology 128 

10.2 The native and alien flora of Switzerland 130 

10.3 The geographic origin of alien 

and naturalized species 131 

10.4 Status of the alien species of Switzerland 133 

10.5 Naturalized species of Switzerland 134 

10.6 Life form 135 

10.7 The habitats of alien plants in Switzerland 136 

10.8 Invasive plant species in Europe 138 

10.9 Discussion 139 

Fact sheets 155

Abstracts 5 

> Abstracts 

Globalization increases trade, travel and transport and is leading to an unprecedented 

homogenization of the world’s biota by transport and subsequent establishment of 

organisms beyond their natural barriers. Some of these alien species become invasive 

and pose threats to the environment and human economics and health. This report on 

alien biota in Switzerland lists about 800 established alien species and characterises 

107 invasive alien species (IAS) in Fact Sheets: five mammals, four birds, one reptile, 

three amphibians, seven fish, four molluscs, 16 insects, six crustaceans, three spiders, 

two «worms», seven fungi, one bacteria, and 48 plants. A general chapter explains 

some common patterns in pathways, impacts and management, and gives recommendations 

for the management of alien species. The main body of the report is organised 

into taxonomic groups, and includes an overview, lists of alien species, Fact Sheets on 

the invasive species, and an evaluation of the status, impacts, pathways, control options 

and recommendations. The Fact Sheets summarize information on the invasive species 

under the headings taxonomy, description, ecology, origin, introduction, distribution, 

impact, management and references. 

Mit der zunehmenden Globalisierung nimmt auch der Handel, Verkehr und das Reisen 

zu und führt zu einer noch nie dagewesenen Homogenisierung der Biodiversität; 

Organismen werden über die natürlichen Grenzen hinaus transportiert. Einige dieser 

Neuankömmlinge können sich etablieren, und wiederum einige von diesen werden 

invasiv und bedrohen die einheimische Vielfalt, richten wirtschaftlichen Schaden an 

oder schädigen die menschliche Gesundheit. Dieser Bericht über die gebietsfremden 

Arten der Schweiz listet über 800 etablierte gebietsfremde Arten auf und stellt die 107 

Problemarten in Datenblättern vor: fünf Säugetiere, vier Vögel, ein Reptil, drei Amphibien, 

sieben Fische, vier Weichtiere, 16 Insekten, sechs Krebstiere, drei Spinnen, zwei 

«Würmer», sieben Pilze, ein Bakterium und 48 Pflanzen. Das erste Kapitel erläutert 

einige allgemeine Einführungswege, negative Einflüsse und Gegenmassnahmen und 

gibt Vorschläge für den Umgang mit gebietsfremden Arten. Der Hauptteil besteht aus 

den Kapiteln zu den einzelnen taxonomischen Gruppen. Die Listen werden begleitet 

durch einen erläuternden Text, die Datenblätter stellen die Problemarten vor und 

schliesslich wird eine Auswertung der Situation, der Auswirkungen, der Einführungswege, 

mögliche Gegensteuerungsmassnahmen und Empfehlungen zu den jeweiligen 

taxonomischen Gruppen gegeben. Die Datenblätter bieten Information zu Taxonomie, 

Beschreibung, Ökologie, Herkunft, Einführungswege, Verbreitung, Auswirkungen, 

Ansätze zur Gegensteuerung und ein Literaturverzeichnis. 

Keywords: 

harmful organisms, 

alien species, 

invasive species, 

biodiversity 

Stichwörter: 

Schadorganismen, 

gebietsfremde Organismen, 

invasive Organismen, 

Biodiversität, 

Neobiota, 

Neophyten, 

Neozooa

An inventory of alien species and their threat to biodiversity and economy in Switzerland FOEN 2006 6 

La mondialisation implique une augmentation du commerce et des transports et en- 

traîne une uniformisation sans précédant des biomes par le transfert et l’implantation 

des organismes vivants au delà de leurs barrières naturelles. Certaines de ces espèces 

exotiques deviennent envahissantes et représentent une menace pour l’environnement, 

l’économie et la santé publique. Ce rapport sur les organismes biologiques exotiques en 

Suisse inventorie environ 800 espèces non-indigènes établies dans le pays et détaille 

107 espèces envahissantes sous forme de fiches d’information : cinq mammifères, 

quatre oiseaux, un reptile, trois amphibiens, sept poissons, quatre mollusques, 16 

insectes, six crustacés, trois araignées, deux « vers », sept champignons, une bactérie et 

48 plantes. Un chapitre général explique les modes d’introduction principaux des 

espèces exotiques et leur impact sur le milieu. Il donne également des recommandations 

sur la gestion et la lutte contre les organismes envahissants. Le corps principal du 

rapport est présenté par groupe taxonomique pour chacun desquels sont proposés une 

discussion générale, la liste des espèces non-indigènes, les fiches d’information sur les 

principales espèces envahissantes et une évaluation du statut, de l’impact, des modes 

d’introduction, les méthodes de lutte et des recommandations générales. Les fiches 

résument pour des espèces particulièrement envahissantes ou potentiellement dangereuses 

les informations sur la taxonomie, la description, l’écologie, l’origine, l’introduction 

en Suisse et en Europe, la distribution, l’impact, la gestion et les références 

bibliographiques. 

La crescente globalizzazione implica un aumento del commercio, dei viaggi e dei 

trasporti e determina un’omogeneizzazione senza precedenti della biodiversità a seguito 

del trasferimento e del successivo insediamento di organismi viventi oltre le loro 

barriere naturali. Alcune di queste specie aliene diventano invasive, minacciano la 

biodiversità locale, causano danni economici o sono nocive per l’uomo. Il presente 

rapporto elenca le oltre 800 specie aliene presenti in Svizzera e propone delle schede 

informative per le 107 specie diventate invasive. Si tratta di cinque mammiferi, quattro 

uccelli, un rettile, tre anfibi, sette pesci, quattro molluschi, 16 insetti, sei crostacei, tre 

aracnidi, due «vermi», sette funghi, un batterio e 48 piante. Il primo capitolo illustra 

alcune delle vie di penetrazione più comuni di tali specie nonché il loro impatto negativo 

sul nostro ambiente. Inoltre, propone possibili contromisure e raccomandazioni per 

la gestione delle specie aliene. La parte centrale del rapporto è suddivisa per gruppi 

tassonomici. Le liste sono corredate di un testo esplicativo, mentre le schede trattano le 

specie problematiche. Infine, il rapporto presenta una valutazione della situazione, 

dell’impatto e delle vie di penetrazione, alcune contromisure e delle raccomandazioni 

concernenti i singoli gruppi tassonomici. Le schede contengono informazioni relative a 

tassonomia, descrizione, ecologia, provenienza, vie di penetrazione, diffusione, impatto, 

eventuali misure di gestione e indicazioni bibliografiche. 

Mots-clés : 

organismes nuisibles, 

organismes exotique, 

organismes envahissants, 

diversité biologique, 

néophytes, 

animaux envahissants, 

plantes envahissantes 

Parole chiave: 

organismi nocivi, 

organismi allogeni, 

organismi invasivi, 

biodiversità, 

neofite, 

animale invasivi, 

piante invasive

Vorwort 7 

> Vorwort 

Die weitgehend durch Klima und Geologie bestimmte Verteilung der Tier- und Pflanzenarten 

auf der Erde wurde lange Zeit durch natürliche Barrieren, wie Meere, Gebirge, 

Wüsten und Flüsse, aufrechterhalten. Mit der Überwindung dieser Barrieren durch 

den Menschen ist, namentlich in den letzten hundert Jahren durch zunehmenden Handel 

und Tourismus, eine neue Situation entstanden. Die Erde ist klein geworden. 

Der Mensch reiste und reist aber nicht alleine. Im «Gepäck» hat er – beabsichtigt oder 

unbeabsichtigt – Pflanzen- und Tierarten mitgeschleppt, von denen einige in der neuen 

Heimat zu massiven Problemen geführt haben. Bekannte Beispiele sind die Ziegen auf 

den Galapagos- Inseln oder die Ratten und Katzen in Neuseeland, die zum Aussterben 

von Arten geführt haben, die einmalig auf der Welt waren. 

Im Gegensatz zu Inseln, die mit ihren spezifisch angepassten Arten einzigartige Ökosysteme 

darstellen, ist Europa bislang weitgehend verschont geblieben von Problemen 

mit gebietsfremden Arten. Über die Ursachen wird spekuliert. Es kann daran liegen, 

dass Europa nie Einwanderungen erlebt hat wie Nord-Amerika oder Australien, wo die 

neuen Siedler mit ihren mitgebrachten Haustieren und Nutzpflanzen einen massiven 

Einfluss auf die vorhandene Flora und Fauna ausgeübt haben. Vielleicht sind aber auch 

unsere Ökosysteme robuster, so dass neue Arten es schwerer gehabt haben, Fuss zu 

fassen und die einheimischen Arten zu verdrängen. 

Allerdings mehren sich auch in Europa und bei uns in der Schweiz heute die Anzeichen 

für Invasionen: Kanadische Goldrute, Riesenbärenklau und Ambrosia sind Beispiele 

aus dem Pflanzenreich, die aktuell durch die Tagespresse gehen. Aus dem 

Tierreich sind es das Grauhörnchen, die Schwarzkopfruderente oder der Amerikanische 

Flusskrebs, die den Naturschützern und Behörden zunehmend Kopfzerbrechen 

bereiten. Und selbst Insekten fallen vermehrt negativ auf, z.B. der Maiswurzelbohrer 

oder der Asiatische Marienkäfer, die unsere Nutzpflanzen direkt oder indirekt bedrohen. 

Die Folgen dieser Entwicklung sind heute noch nicht abschätzbar. 

Nach der Biodiversitätskonvention ist die Schweiz verpflichtet, Massnahmen gegen 

invasive gebietsfremde Arten zu ergreifen und deren Verbreitung einzudämmen oder 

zu verhindern. Nach dem Motto «Gefahr erkannt – Gefahr gebannt» ist es für die 

Schweiz von zentraler Bedeutung, potenziell gefährliche Arten zu erkennen. Das 

vorliegende Kompendium ist hierfür gedacht. Es beschreibt in umfassender Weise von 

den Flechten bis hin zu Säugetieren gebietsfremde Arten mit Schadenpotenzial, die 

schon hier sind oder die vor den Toren der Schweiz stehen. 

Georg Karlaganis 

Head of Substances, Soil and Biotechnology Division 

Federal Office for the Environment (FOEN)


> Summary 

Globalization is increasing trade and travel on an unprecedented scale, and has inadvertently 

led to the increased transport and introduction of alien species, breaking down 

the natural barriers between countries and continents. Alien species are not bad per se, 

in fact many species are beneficial for humans, e.g. most crop species. However, some 

alien species have become harmful, and pose threats to the environment and humans. 

Invasive alien species (IAS) are increasingly recognized as one of the major threats to 

biodiversity. 

All signatories to the Convention on Biological Diversity (CBD), including Switzerland, 

have agreed to prevent the introduction of, control or eradicate those alien species 

which threaten ecosystems, habitats or species. 

There is a widespread view that IAS are of less concern in Central Europe than on 

other continents (and more especially on islands). Possible reasons for this include the 

small size of nature reserves, the high human impact on all ‘natural’ environments, and 

the long association of alien species and humans leading to familiarisation and adaptation. 

However, the number of cases of dramatic impact is increasing and awareness 

among scientists and the public is steadily growing. Thus, the threats from IAS should 

not be underrated. One of the major consequences, which is undoubtedly unfolding 

before our eyes, is global homogenization, with the unique character of places such as 

Switzerland being lost, the characteristic flora and fauna invaded by organisms which 

reproduce to eventually form the largest proportion of biomass in certain ecosystems. 

Time lags, i.e. the gap between establishment and invasion, makes prediction of invasiveness 

of alien species very difficult. Well-established species showing no hint of any 

harm to the environment may still become invasive in the future. There are three major 

categories of factors that determine the ability of a species to become invasive: intrinsic 

factors or species traits; extrinsic factors or relationships between the species and 

abiotic and biotic factors; and the human dimension, incorporating the importance of 

species to humans. 

This report compiles information about alien species in Switzerland from published 

sources and experts in Switzerland and abroad. Imminent future bioinvasions are also 

included. The availability of national lists varies greatly between taxonomic groups. 

Thus, unfortunately, it is not possible to list all the alien species of Switzerland, since 

not all resident species are known yet. However, for groups that are well known, 

complete lists have been compiled. For some groups only invasive species rather than 

alien species are treated, and other groups could not be covered at all. 

The broad taxonomic groupings used are vertebrates, crustaceans, insects, arachnids, 

molluscs, other animals, fungi and plants. For each group, we present an overview, a 

list of alien species, Fact Sheets for the invasive species, an evaluation of the status,

Summary 9 

impacts, pathways and control options for the group, and recommendations. The Fact 

Sheets summarize information on the invasive species under the headings taxonomy, 

description, ecology, origin, introduction, distribution, impact, management and references. 

Definitions of the important terms used in the report are given, since frequently-used 

terms such as ‘invasive’ are often used in different ways. 

The situation regarding IAS in Switzerland is similar to that in other Central European 

countries, in particular Austria, which is also a land-locked country containing part of 

the Alps. This report lists about 800 alien species and characterises 107 IAS in Fact 

Sheets: five mammals, four birds, one reptile, three amphibians, seven fish, four molluscs, 

16 insects, six crustaceans, three spiders, two ‘worms’, seven fungi, one bacteria, 

and 48 plants. 

Pathways can be divided into those for species deliberately introduced and those for 

species accidentally introduced. Pathways for deliberate introductions include the trade 

of species used in aquaculture, for fisheries, as forest trees, for agricultural purposes, 

for hunting, for soil improvement and solely to please humans as ornamentals. Most of 

these can also transport hitchhiking species and people can accidentally introduce 

species while travelling. In general, most aquatics and terrestrial invertebratesand 

diseases are accidental arrivals, whereas most plants and vertebrates are deliberately 

introduced. The global trend for the latter groups also holds true for Switzerland, e.g. 

75 % of the 20 Black List plants were introduced principally as ornamentals, and 35 of 

the 37 vertebrates were deliberately introduced. Thus, many damaging invaders were 

deliberately introduced, often with little justification beyond the wish to “improve” the 

landscape, e.g. ornamental plants and waterfowl. 

The impacts of IAS are often considerable, in particular when ecosystem functioning is 

altered or species are pushed to extinction, as has been shown for many bird species on 

islands. The environmental impacts can be divided into four major factors: competition, 

predation, hybridization and transmission of diseases. The most obvious examples 

for competition are between introduced and native plants for nutrients and exposure to 

sunlight. Resource competition has also led to the replacement of the native red squirrel 

(Sciurus vulgaris) by the introduced American grey squirrel (S. carolinensis) in 

almost all of Great Britain and it is predicted that this trend will continue on the continent. 

The musk rat (Ondatra zibethicus) causes declines of native mussels population 

(Unionidae) by predation and the amphipod Dikerogammarus villosus is a serious 

predator of native freshwater invertebrates. A well-known example of hybridization 

from Europe is the ruddy duck (Oxyura jamaicensis), which hybridizes with the endangered 

native white-headed duck (O. leucocephala). In some cases IAS can harbour 

diseases and act as a vector for those diseases to native species. This is the case with 

American introduced crayfish species to Europe, which are almost asymptomatic 

carriers of the alien crayfish plague (Aphanomyces astaci), but the native noble crayfish 

(Astacus astacus) is highly susceptible to the disease, and thus is struggling to 

coexist with populations of the American crayfish species.


In addition to impacts on biodiversity, many IAS cause enormous economic costs. 

These costs can arise through direct losses of agricultural and forestry products and 

through increased production costs associated with control measures. A North American 

study calculated costs of US$ 138 billion per annum to the USA from IAS. A 

recently released report estimates that weeds are costing agriculture in Australia about 

Aus$ 4 billion a year, whereas weed control in natural environments cost about Aus$ 

20 million in the year from mid 2001 to mid 2002. In Europe, the costs of giant hogweed 

(Heracleum mantegazzianum) in Germany are estimated at € 10 million; € 1 

million relating to each of the environment and health sectors, and the remainder 

represents costs to the agricultural and forestry sectors. Economic damage by the 

western corn rootworm (Diabrotica virgifera) is increasing as it spreads through 

Europe. Some IAS also have implications for human health, e.g. giant hogweed produces 

copious amounts of a sap containing phototoxic substances (furanocoumarins), 

which can lead to severe burns to the skin. The raccoon dog (Nyctereutes procyonoides), 

introduced as a fur animal, can, like the native red fox (Vulpes vulpes), act as a 

vector of the most dangerous parasitic disease vectored by mammals to humans in 

Central Europe, i.e. the fox tapeworm (Echinococcus multilocularis). Known impacts 

of species introduced into Switzerland are presented, although some recent invaders 

have not yet been reported to have impact in Switzerland; in these cases impacts assessed 

in other countries are given. Demonstration of environmental impacts is often 

difficult because of the complexity of ecosystems, but alien species occurring in high 

numbers, such as Japanese knotweed (Reynoutria japonica) totally covering riversides, 

or an animal biomass of alien species of up to 95 % in the Rhine near Basel, must have 

impacts on the native ecosystem. All species use resources and are resources to other 

creatures and so they alter the web and nutrient flow of the ecosystems they are living 

in. 

Recommendations for the management – in its widest sense – of groups of invasives 

and individual species are given in the respective chapters and Fact Sheets. Preparing a 

national strategy against IAS is recommended to deal with IAS in an appropriate way 

and as anticipated by the CBD. This action plan should identify the agency responsible 

for assessing the risks posed by introductions, provide funding mechanisms and technical 

advice and support for control options. Prevention measures against further bioinvasions 

need to be put in place to stem the tide of incoming new species arriving 

accidentally with trade and travel or introduced deliberately for various purposes. New 

deliberate introductions must be assessed as to the threat they may present and only 

introduced on the basis of a risk analysis and environmental impact assessment. This 

report indicates some important pathways for consideration and shows that most 

invasive species are deliberately introduced. The use of native plants and non-invasive 

alien plants for gardening and other purposes should be promoted. Laws regulating 

trade in plant species on the Black List would be a first step in the right direction to 

reduce the impact of these species. However, restrictions for species already widely 

distributed within Switzerland will not drastically change the situation unless the 

populations already present are eradicated or controlled. Fish introductions are regulated 

by the Fisheries Act, which names those species for which an authorization for 

release is needed, and species for which release is prohibited altogether. This is a good 

basis, although the law could be better adapted to the current situation, as described in

Summary 11 

the fish section. The aquarium and terrarium trade is another important sector that 

could be more strictly regulated to stop releases of pets into the wild. A major problem 

with introductions of IAS is that the costs when they invasive are borne by the public, 

while the financial incentives for introducing them lie with individuals or specific 

businesses. Development of economic tools that shift the burden of IAS to those who 

benefit from international trade and travel is a neglected approach (also called the 

‘polluter pays’ principle). Appropriate tools would be fees and taxes, including fees 

levied on those who import the organisms or goods. Awareness raising is a significant 

tool in the prevention and management of IAS, since some member of the public would 

adhere to advice if they knew about its importance and the reason for it. Scientists and 

decision-makers also need better access to information about invasive species, their 

impacts, and management options. To address the impacts of those invasive species 

already present in Switzerland, their populations need to be managed: either eradicated 

or controlled. Possible targets for eradication are the sika deer (Cervus nippon), the 

mouflon (Ovis orientalis), and the ruddy shelduck (Tadorna ferruginea), which will 

otherwise increase its range and spread to neighbouring countries. A pilot national 

eradication / control programme against a prominent invader, e.g. a Black List plant 

species, is recommended as a case study. Monitoring populations of some alien species 

is recommended to detect any sudden increases indicating potential invasiveness. By 

doing this, control or even eradication efforts can be employed before the populations 

become unmanageable. While compiling the information for this report it became clear 

that more information about the status of IAS in Switzerland is needed. More studies 

on alien species are highly recommended to assess the importance of IAS and to demonstrate 

their significance to policy-makers and politicians. 

Limited resources dictate the need for setting priorities and allocating funds where it 

will have the greatest impact in combating IAS. Important points, for example, are to 

critically assess the feasibility of different approaches, and to target species for which 

there is no conflict of interest. Opposition to action against less-important ornamentals 

on the Black List and species of direct human health concern (giant hogweed) should 

be negligible.


> Zusammenfassung 

Mit der zunehmenden Globilisierung ist ein starker Anstieg des Warentransportes, 

Verkehrs und Tourismus zu verzeichnen. Dies führt zu ungewollten wie beabsichtigten 

Einführungen von gebietsfremden Arten in einem noch nie dagewesenen Umfang, und 

der Verschmelzung von Biodiversitäten der unterschiedlichen Länder und Kontinente, 

so dass nur schwer zu überbrückende natürliche Ausbreitungsschranken plötzlich 

überwunden werden. Nicht alle gebietsfremden Arten sind automatisch als negativ zu 

bewerten. Tatsächlich sind viele Arten wichtige Bestandteile der Ökonomie eines 

Landes, man denke nur an die zahlreichen gebietsfremden Kulturpflanzen. Einige 

Arten entwickeln sich allerdings zu Problemarten und bedrohen die einheimische 

Biodiversität, richten wirtschaftlichen Schaden an oder stellen eine Gefahr für die 

Gesundheit dar. 

Gebietsfremde Problemarten (invasive alien species) werden heute als eine Hauptbedrohung 

für die Biodiversität angesehen. Die Biodiversitätskonvention (CBD) verpflichtet 

die internationale Staatengemeinschaft Vorsorge gegen diese invasiven Arten 

zu treffen und diese gegebenenfalls zu bekämpfen. 

Gebietsfremde Arten in Zentraleuropa werden oft als geringes Problem eingestuft, im 

Vergleich zu anderen Kontinenten und vor allem Inseln. Mögliche Gründe für diese 

Unterschiede sind die relativ kleinen Schutzgebiete, was die Möglichkeit für eine 

intensive Pflege eröffnet, die stark vom Menschen beeinflussten ‘Naturräume’ und das 

lange Zusammenleben von vielen gebietsfremden Arten mit dem Menschen, das zu 

vielfältigen Anpassungen geführt hat. Trotzdem nehmen die Fälle von dramatischen 

Auswirkungen von gebietsfremden Arten und das Bewusstsein in der Bevölkerung und 

bei den Wissenschaftlern zu. Zweifellos ist die globale Homogenisierung in vollem 

Gange und der einzigartige Charakter von lokalen Ökosystemen, wie zum Beispiel in 

der Schweiz, gehen für immer verloren, da die charakteristische Pflanzen- und Tierwelt 

von gebietsfremden Arten verändert wird und einige dieser Arten die grössten Anteile 

an der Biomasse von einigen Ökosystemen erreichen. 

Die Zeitdifferenz, die zwischen der Ankunft einer Art und ihrer starken Ausbreitung 

auftreten kann, macht Voraussagungen der Invasivität von Arten aussserordentlich 

schwierig. Einige schon lange etablierte Arten können plötzlich und unerwartet invasiv 

werden. Drei Kategorien von Faktoren bestimmen die Invasivität von Arten: 1. die 

biologischen Merkmale einer Art, 2. das Zusammenspiel einer Art mit ihrer abiotischen 

und biotischen Umwelt und 3. die Beziehungen der Menschen zu dieser Art. 

In diesem Bericht ist Information über gebietsfremde Arten der Schweiz sowohl von 

publizierten Dokumenten als auch von direktem Austausch mit Experten in der 

Schweiz und des Auslandes zusammengetragen. Bevorstehende Einwanderungen sind 

ebenfalls erfasst worden. Die Verfügbarkeit von Artenlisten in den einzelnen taxonomischen 

Gruppen ist sehr unterschiedlich, so dass es nicht möglich ist alle gebiets-


fremden Arten zu benennen. In einigen Gruppen ist das Wissen sogar der einheimische 

Arten so rudimentär, dass kein Versuch gemacht wurde, sie zu bearbeiten, und bei 

anderen Gruppen wurden nur Problemarten aufgenommen. Die Listen der gebietsfremden 

Arten wieder anderer Gruppen dagegen sind vollständig. 

Die gebietsfremden Organismen wurden in folgende Gruppen aufgeteilt: Wirbeltiere, 

Krebstiere, Insekten, Spinnentiere, Weichtiere, andere Tiere, Pilze und Pflanzen. In 

jedem Kapitel befinden sich die Listen der gebietsfremden Arten, ein erläuternder Text, 

Datenblätter der Problemarten und eine Auswertung der Situation, der negativen 

Auswirkungen, der Einführungswege, der möglichen Gegensteuerungsmassnahmen 

und Empfehlungen für den Umgang mit diesen Arten. Die Datenblätter bieten Information 

zu Taxonomie, Beschreibung, Ökologie, Herkunft, Einführungswege, Verbreitung, 

Auswirkungen, Ansätze zur Gegensteuerung und ein Literaturverzeichnis. 

Definitionen der wichtigsten Begriffe, wie sie in diesem Dokument benutzt werden, 

werden ebenfalls gegeben, da sie oftmals unterschiedlich gebraucht werden. 

Die Situation der gebietsfremden Arten der Schweiz ist ähnlich wie in anderen mitteleuropäischen 

Ländern, vor allem Österreich, das eine ähnliche Topographie besitzt. 

Dieser Bericht über die gebietsfremden Arten der Schweiz listet über 800 etablierte 

gebietsfremde Arten auf und stellt die 107 Problemarten in Datenblättern vor: fünf 

Säugetiere, vier Vögel, ein Reptil, drei Amphibien, sieben Fische, vier Weichtiere, 16 

Insekten, sechs Krebstiere, drei Spinnen, zwei ‘Würmer’, sieben Pilze, ein Bakterium 

und 48 Pflanzen. 

Es können versehentlich eingeschleppte Arten und bewusst eingeführte Arten unterschieden 

werden. Eingeführt sind zum Beispiel Arten der Aquakulturen, der Fischerei, 

der Waldwirtschaft, der Landwirtschaft, der Jagd, zur Bodenverbesserung und einfach 

zur Bereicherung der Landschaft, wie Zierpflanzen. Viele der eingeführten Arten 

können allerdings andere Arten auf und in sich tragen und so einschleppen, und der 

reisende Mensch transportiert ebenfalls oftmals gebietsfremde Arten. Die meisten 

aquatischen und terrestrischen Wirbellosen und Krankheiten wurden versehentlich 

eingeschleppt, während Pflanzen und Wirbeltiere meist eingeführt worden sind. Dieser 

globale Trend findet sich auch bei den gebietsfremden Arten der Schweiz wieder, denn 

75 % der 20 Arten auf der ‘Schwarzen Liste’ wurden als Zierpflanzen eingeführt und 

35 der 37 Wirbeltiere wurde zu einem bestimmten Zweck importiert. Das heisst, dass 

viele der Problemarten bewusst eingeführt wurden, oftmals mit einer geringfügigen 

Rechtfertigung, z.B. um die Landschaft mit Zierpflanzen und Wasservögeln zu ‘bereichern’. 

Die Auswirkungen, die gebietsfremde Arten auslösen können, sind oft beträchtlich, vor 

allem wenn die Funktion eines Ökosystems gestört wird, einheimische Arten verdrängt 

werden oder sogar aussterben, wie es bei Vogelarten auf Inseln dokumentiert worden 

ist. Vier Faktoren können zu solchen Problemen führen: 1. Konkurrenz zu einheimischen 

Arten, 2. ein gebietsfremder Räuber, 3. die Hybridisierung mit einheimischen 

Arten und 4. die Ausbreitung von Krankheiten durch einen gebietsfremden Vektor. 

Offensichtliche Beispiele für Konkurrenz sind der Kampf um Licht und Nährstoffe


zwischen gebietsfremden und einheimischen Pflanzenarten. Der Konkurrenzkampf um 

Nahrung hat in Grossbrittanien zur fast völligen Verdrängung des Eichhörnchens 

(Sciurus vulgaris) durch das eingeführte Grauhörnchen (S. carolinensis) geführt und es 

ist zu befürchten, dass dieser Trend auch auf dem Festland weitergehen wird. Der 

Bisam (Ondatra zibethicus) hat als Räuber der einheimischen Muscheln (Unionidae) 

zu ihrem Rückgang beigetragen und der Amphipode Dikerogammarus villosus ist ein 

grosser Feind der einheimischen Wirbellosen der Gewässer. Ein bekanntes Beispiel für 

eine Hybridisierung ist die eingeführte Schwarzkopf-Ruderente (Oxyura jamaicensis), 

die sich mit der stark gefährdeten Weisskopf-Ruderente (O. leucocephala) verpaart. In 

einigen Fällen können gebietsfremde Arten Krankheiten unter einheimischen Arten 

verbreiten. Dies ist der Fall bei der berüchtigten Krebspest (Aphanomyces astaci), die 

von ebenfalls eingeführten nordamerikanischen Flusskrebsen, die fast keine Symptome 

zeigen, auf den einheimischen Flusskrebs (Astacus astacus), der dramatisch mit einem 

sofortigen Zusammenbruch der Population reagiert, übertragen werden. 

Neben diesen Auswirkungen auf die Umwelt, können gebietsfremde Arten auch enorme 

ökonomische Schäden verursachen. Die Kosten können durch den Verlust von 

land- und forstwirtschaftlichen Produkten und durch erhöhte Produktionskosten durch 

Bekämpfungsmassnahmen entstehen. Eine nordamerikanische Studie hat die jährlichen 

Kosten von gebietsfremden Arten in der USA auf 13,8 Milliarden US Dollar berechnet. 

Ein anderer Bericht schätzt die Kosten durch Unkräuter für die australische Landwirtschaft 

auf 4 Milliarden Australische Dollar, und 20 Millionen Aus. $ wurden während 

eines Jahres zwischen Mitte 2001 und Mitte 2002 für die Unkrautbekämpfung auf 

naturnahen Flächen ausgegeben. Die Kosten durch den Riesenbärenklau (Heracleum 

mantegazzianum) in Deutschland werden auf 10 Millionen € geschätzt, wobei je eine 

Millionen im Umweltbereich und Gesundheitswesen anfallen und der Rest in Landwirtschaft 

und Forst. Der Westliche Maiswurzelbohrer (Diabrotica virgifera) dehnt 

seine Verbreitung weiter nach Nordwesten aus und bereitet grosse Schäden an den 

Maiskulturen. Einige gebietsfremde Arten schaden der menschlichen Gesundheit, so 

produziert der Riesenbärenklau grosse Mengen eines Saftes der phototoxische Substanzen 

(Furanocumarine), die zu starken Verbrennungen der Haut führen können, 

enthält. Der Marderhund (Nyctereutes procyonoides), als Pelztier eingeführt, kann, wie 

der einheimische Rotfuchs (Vulpes vulpes), als Vektor des Fuchsbandwurmes (Echinococcus 

multilocularis), der gefährlichsten Krankheit, die in Zentraleuropa von Säugetieren 

auf den Menschen übertragen wird, fungieren. Für diesem Bericht wurden 

bekannte Auswirkungen von gebietsfremden Arten in der Schweiz zusammengetragen. 

Für Arten, die noch nicht lange in der Schweiz vorkommen, wurde auf Berichten von 

Auswirkungen in anderen Ländern zurückgegriffen. Es muss erwähnt werden, dass 

Nachweise von Auswirkungen einer gebietsfremden Art in einem komplexen Ökosystem 

oft schwierig zu führen sind. Andererseits ist es offensichtlich, dass Arten wie der 

Japanische Staudenknöterich (Reynoutria japonica), der oft ganze Flussufer säumt, 

oder eine tierische Biomasse von gebietsfremden Arten von 95 % im Rhein bei Basel, 

eine Auswirkung auf das Ökosystem haben müssen. Alle Arten verbrauchen Nährstoffe 

und dienen als Nährstoff für andere Organismen und ändern so das Nahrungsnetz und 

den Nährstofffluss der Ökosysteme, die sie besiedeln.


In den Texten der jeweiligen Kapitel und den Datenblättern sind Empfehlungen zur 

Gegensteuerung (Prävention und Kontrolle) für die Gruppen und einzelnen Arten 

gegeben. Allgemein ist die Erstellung einer Nationalen Strategie im Hinblick auf 

gebietsfremde Arten zu empfehlen, um angemessene Schritte ergreifen zu können, und 

es von der Biodiversitätskonvention gefordert ist. Dieser Plan sollte eine zuständige 

Behörde identifizieren, die die Risiken von Einführungen und Einschleppungen beurteilt, 

für finanzielle Mittel sorgt und technische Unterstützung zur Bekämpfung bereitstellt. 

Massnahmen zur Prävention um weitere Bioinvasionen zu stoppen oder zu 

vermindern müssen ausgearbeitet werden. Einführungen von neuen Organismen sollten 

vorher auf ihre möglichen Gefahren für die Umwelt untersucht werden und nur auf der 

Basis einer Risikoanalyse eingeführt werden. Die Analyse der wichtigsten Einführungswege 

zeigt unmissverständlich, dass die meisten Problemarten bewusst eingeführt 

wurden (und werden). Die Nutzung von einheimischen Arten und fremden Arten ohne 

Potential zur Invasivität zum Beispiel in Gärten, Parks und Forsten sollte mehr gefördert 

werden. Gesetze, die den Handel mit Pflanzenarten der ‘Schwarzen Liste’ regeln, 

wären ein konsequenter nächster Schritt, um die Auswirkungen dieser Arten zu reduzieren. 

Wenn die Arten allerdings schon eine weite Verbreitung in der Schweiz besitzen, 

können nur Kontrollmassnahmen oder eine erfolgreiche Ausrottung Abhilfe 

schaffen. Die Fischereiverordnung reguliert Fischaussetzungen, indem sie Arten benennt 

für die eine Bewilligung nötig ist und Arten, deren Aussetzung verboten ist. 

Diese solide Basis könnte noch verbessert werden, um der Situation besser zu entsprechen, 

wie in dem Teil über Fische beschrieben. Ein weiterer Sektor, der mehr reguliert 

werden sollte, ist der Handel mit Haustieren (vor allem Aquarium and Terrarium), der 

immer wieder zu Aussetzungen führt. Ein Grundproblem der Einführungen ist, dass die 

Kosten von Problemarten von der Öffentlichkeit getragen werden, während der finanzielle 

Nutzen der Einführung einzelnen Importeuren oder bestimmten Wirtschaftszweigen 

zugute kommt. Die Entwicklung von ökonomischen Programmen, die die Last 

auf die verteilt, die auch den Nutzen aus der Einfuhr haben, ist ein vernachlässigter 

Denkansatz (Verursacherprinzip genannt). Möglichkeiten wären gegeben durch die 

Erhebung von Gebühren und Steuern, die für den Importeur zu bezahahlen wären. Eine 

wichtige Vorgehensweise, um die Probleme mit gebietsfremden Arten unter Kontrolle 

zu kriegen, ist die Schaffung eines geschärftes Bewusstseins der Problematik in der 

Bevölkerung. Wissenschaftler und Entscheidungsträger benötigen ebenfalls mehr 

Information über gebietsfremde Problemarten, deren Auswirkungen und den Möglichkeiten 

für eine Gegensteuerung. Einige Problemarten müssten bekämpft oder ausgerottet 

werde, um ihre Auswirkungen wirkungsvoll zu minimieren. Mögliche Zielarten für 

eine Ausrottung sind der Sikahirsch (Cervus nippon), das Mufflon (Ovis orientalis) 

oder die Rostgans (Tadorna ferruginea), die sonst ihre Verbreitung weiter ausdehnt 

und die Nachbarländer erreichen wird. Für eine erste grossangelegte Ausrottung oder 

Bekämpfung ist ebenfalls eine Pflanzenart der ‘Schwarzen Liste’ zu empfehlen. Ausserdem 

wäre die Beobachtung der Populationen von gebietsfremden Arten empfehlenswert, 

um etwaige starke Zunahmen früh zu erkennen. In diesem Fall könnten 

Gegenmassnahmen ergriffen werden, bevor die Populationen zu gross werden. Beim 

Zusammentragen der Informationen wurde schnell klar, dass viel mehr Information 

über gebietsfremde Arten benotigt wird. Daher sind mehr Studien zur Bedeutung von 

gebietsfremden Arten nötig, um Entscheidungsträger und Politiker auf die Lage aufmerksam 

zu machen.


Die limitierten Ressourcen, die zur Verfügung stehen, zwingen Prioritäten zu setzen, 

um die finanziellen Mittel dort einzusetzen, wo sie die meiste Wirkung zeigen im 

Kampf gegen Problemarten. Dabei müssen wichtige Punkte berücksichtigt werden, 

etwa, welche Methode den grössten Nutzen bringt, oder welche Arten für Bekämpfungsmassnahmen 

zuerst in Betracht gezogen werden sollten. Arten mit einem hohen 

Potenzial für Konflikte versprechen weniger Erfolg. Wenn Arten der ‘Schwarzen 

Liste’, welche keine grosse Wichtigkeit als Zierpflanzen besitzen, oder Arten die den 

Menschen gefährden, als Ziele ausgewählt werden, ist der zu erwartende Widerstand 

gegen Massnahmen eher gering einzuschätzen.

Résumé 17 

> Résumé 

La globalisation a pour effet une augmentation sans précédant du commerce et des 

transports, dont une des conséquences est l’accroissement des déplacements et introductions 

d’espèces exotiques. Les espèces exotiques ne sont pas toutes nuisibles. En 

fait un grande nombre d’entre elles sont bénéfiques, comme par exemple les nombreuses 

plantes cultivées d’origine étrangère. Cependant, certaines espèces exotiques deviennent 

nuisibles et posent des problèmes à l’environnement et à l’homme en général. 

Les Espèces Exotiques Envahissantes (EEE) sont de plus en plus reconnues comme 

une des menaces les plus sérieuses posées à la biodiversité. 

Tous les pays signataires de la convention sur la diversité biologique (CDB), dont la 

Suisse, se sont engagés à prévenir l’introduction, à contrôler ou éradiquer les espèces 

exotiques menaçant les écosystèmes, les habitats ou les espèces. 

Il est communément avancé que les EEE causent moins de problèmes en Europe 

Centrale que dans d’autres continents ou régions. Les raisons possibles sont, entre 

autres, la taille limitée des réserves naturelles, l’impact humain important dans tous les 

milieux « naturels » et la longue association, en Europe, entre les espèces exotiques et 

l’homme, ayant conduit à une familiarisation de ces espèces et une adaptation à 

l’environnement humain. Cependant, le nombre de cas d’espèces exotiques causant des 

dégâts importants est en augmentation en Europe, un phénomène dont les chercheurs, 

mais également le public, ont de plus en plus conscience. De fait, la menace des espèces 

envahissantes ne doit pas être sous-estimée. Une des conséquences les plus visibles 

est le phénomène d’uniformisation, menant à la perte de paysages uniques, y compris 

en Suisse. La flore et la faune caractéristiques sont de plus en plus envahies par les 

organismes exotiques qui se reproduisent, pour finalement composer la plus grande 

partie de la biomasse de certains écosystèmes. 

Le délai qui s’écoule entre la phase d’établissement et d’invasion d’une espèce exotique 

(‘time lag’), rend la prédiction du phénomène d’invasion très difficile. Des espèces 

bien établies qui n’ont actuellement aucun impact reconnu sur l’environnement peuvent 

malgré tout devenir envahissantes dans le futur. Trois catégories de facteurs 

déterminent la capacité d’une espèce à devenir envahissante: les facteurs intrinsèques 

liés à l’espèce, les facteurs extrinsèques, c.-à-d. les relations entre l’espèce et les facteurs 

biotiques ou abiotiques, et la dimension humaine, par exemple l’importance de 

l’espèce pour l’homme. 

Ce rapport est une compilation des connaissances sur les espèces exotiques en Suisse, 

rassemblées à partir de publications et d’avis d’experts suisses et étrangers. Des informations 

sur les invasions biologiques imminentes sont également inclues. La connaissance 

des espèces présentes en Suisse variant fortement d’un groupe taxonomique à 

l’autre (pour certains taxa, même les espèces indigènes sont loin d’être toutes connues), 

il n’a malheureusement pas été possible d’établir une liste exhaustive d’espèces exoti-


ques pour tous les groupes. Une liste complète a été établie seulement pour les groupes 

taxonomiques bien connus. Pour certains groupes, seules les espèces envahissantes ont 

été compilées alors que quelques groupes n’ont pas pu être traités. 

Les grands groupes taxonomiques traités sont les vertébrés, les crustacés, les insectes, 

les arachnides, les mollusques, les autres animaux, les champignons et les plantes. Pour 

chaque groupe, nous présentons une discussion générale, la liste des espèces nonindigènes, 

les fiches d’information sur les espèces envahissantes et une évaluation du 

statut, de l’impact, des modes d’introduction, les méthodes de lutte et des recommandations 

générales. Les fiches d’information résument, pour des espèces particulièrement 

envahissantes ou potentiellement dangereuses, les informations sur la taxonomie, la 

description, l’écologie, l’origine, l’introduction en Suisse et en Europe, la distribution, 

l’impact, la gestion et les références bibliographiques. 

Les définitions des termes anglais les plus importants utilisés dans ce rapport sont 

données, parce que les mots fréquemment utilisés comme « invasive » sont parfois 

utilisés dans des sens différents. 

La situation concernant les EEE en Suisse est similaire à celle d’autres pays d’Europe 

Centrale, en particulier l’Autriche, un pays également enclavé et Alpin. Ce rapport 

inventorie environ 800 espèces non-indigènes et détaille 107 espèces envahissantes 

sous forme de fiches d’information : cinq mammifères, quatre oiseaux, un reptile, trois 

amphibiens, sept poissons, quatre mollusques, 16 insectes, six crustacés, trois araignées, 

deux « vers », sept champignons, une bactérie et 48 plantes. 

Les modes d’introduction des espèces exotiques sont différents selon qu’il s’agit 

d’espèces délibérément introduites ou d’espèces introduites accidentellement. Les 

introductions délibérées concernent principalement les espèces importées pour l’aquaculture, 

la pêche, la chasse, la sylviculture, l’agriculture, l’horticulture et la protection 

des sols. Les organismes introduits involontairement sont souvent transportés par 

inadvertance avec d’autres importations ou par des voyageurs. En général, la plupart 

des invertébrés et des pathogènes ont été introduits accidentellement, alors que les 

plantes et les vertébrés l’ont souvent été intentionnellement. Cette tendance est également 

valable pour la Suisse. Sur les 20 plantes envahissantes de la liste noire, 75 % ont 

été introduites principalement en tant que plantes ornementales et 35 des 37 vertébrés 

exotiques établis en Suisse ont été introduits délibérément. Il est donc important de 

constater que beaucoup d’envahisseurs, dont certains parmi les plus nuisibles, ont été 

introduits intentionnellement, souvent sans autre soucis que d’améliorer le paysage, 

comme c’est le cas pour les plantes et animaux d’ornement. 

L’impact des EEE est parfois considérable, en particulier quand l’envahisseur altère le 

fonctionnement d’un écosystème ou pousse les espèces indigènes vers l’extinction, 

comme cela a été souvent observé avec les oiseaux en milieu insulaire. Les impacts 

écologiques peuvent être causés par quatre mécanismes majeurs : la compétition, la 

prédation, l’hybridation et la transmission de maladies. Parmi les exemples les plus 

significatifs de compétition, nous pouvons citer la compétition entre les plantes indigènes 

et exotiques pour les nutriments et la lumière. La compétition pour les ressources a

Résumé 19 

également conduit au remplacement de l’écureuil roux indigène (Sciurus vulgaris) par 

l’écureuil gris américain (S. carolinensis) dans la plus grande partie de la Grande- 

Bretagne, et on s’attend à un même phénomène sur le continent. Le rat musqué (Ondatra 

zibethicus) est responsable du déclin des populations de moules indigènes par 

prédation, et l’amphipode Dikerogammarus villosus est un sérieux prédateur des 

invertébrés aquatiques indigènes. Un exemple bien connu d’hybridation en Europe est 

illustré par l’érismature rousse (Oxyura jamaicensis), un canard américain qui 

s’hybride avec l’érismature à tête blanche (O. leucocephala), une espèce européenne en 

danger d’extinction. Dans certains cas, les EEE peuvent abriter des maladies et agir 

comme vecteur d’infection pour les espèces indigènes. C’est le cas des espèces américaines 

d’écrevisse introduites en Europe, porteuses résistantes de la peste de l’écrevisse 

(Aphanomyces astaci), alors que l’écrevisse européenne (Astacus astacus) est très 

sensible à la maladie et a du mal à survivre au côté des espèces américaines introduites. 

En plus des impacts sur la biodiversité, les EEE ont des impacts considérables pour 

l’économie. Ces impacts économiques peuvent être liés aux pertes directes de produits 

agricoles ou forestiers ou à l’augmentation des coûts de production associés à la lutte 

contre les envahisseurs. Une étude américaine a calculé que les EEE coûtait aux Etats- 

Unis la somme de 138 milliards de dollars par an. De même, un récent rapport australien 

estime que les mauvaises herbes coûtent à l’agriculture australienne environ 4 

milliards de dollars australiens par an et que le coût de la lutte contre les plantes envahissantes 

dans les milieux naturels atteint 20 millions de dollars par an. En Europe, le 

coût de la berce du Caucase (Heracleum mantegazzianum) est estimé à € 10 millions 

en Allemagne, un million chacun pour les secteurs de l’environnement et de la santé 

publique, le reste représentant le coût pour les secteurs agricoles et forestiers. L’impact 

économique de la chrysomèle des racines du maïs (Diabrotica virgifera) augmente en 

même temps que sa dissémination en Europe. Certaines EEE ont un impact sur la santé 

publique. Par exemple, la berce du Caucase contient des substances phototoxiques 

(furanocoumarines) qui peuvent causer des brûlures sérieuses. Le chien viverrin (Nyctereutes 

procyonoides), introduit pour sa fourrure, peut, comme le renard indigène 

(Vulpes vulpes), être vecteur le l’échinococcose du renard (Echinococcus multilocularis 

), une dangereuse maladie parasitaire pouvant être transmise à l’homme. Les impacts 

connus des espèces introduites en Suisse sont présentés dans ce rapport. Comme 

plusieurs envahisseurs récents n’ont pas encore montré d’impacts écologiques en 

Suisse, les impacts observés dans d’autres pays sont également présentés. Mesurer les 

impacts écologiques des EEE est souvent une tâche difficile à cause de la complexité 

des écosystèmes. Cependant, les espèces exotiques présentes en très grand nombre, 

comme la renouée du Japon qui couvre totalement les bords de certaines rivières, ou 

une faune aquatique exotique composant 95 % de la biomasse animale dans le Rhin 

près de Bâle ont forcément un impact important sur les écosystèmes indigènes. Toutes 

les espèces utilisent des ressources et sont elle-mêmes ressources d’autres organismes 

vivants et, de ce fait, les espèces exotiques altèrent les chaînes alimentaires des écosystèmes 

dans lesquelles elles ont été introduites. 

Des recommandations pour la gestion (au sens le plus large) des espèces envahissantes 

sont données dans les chapitres respectifs et les fiches d’information. Une stratégie 

nationale appropriée contre les EEE est recommandée afin de gérer le problème de la


manière la plus appropriée, selon les exigences de la CDB. Le plan d’action devrait 

identifier l’agence responsable pour l’évaluation des risques posés par les introductions 

et proposer les mécanismes de financement ainsi que le support technique pour les 

moyens de lutte. Des mesures de prévention contre les invasions biologiques futures 

doivent être mises en place pour contenir l’implantation de nouvelles espèces, qu’elles 

soient accidentellement introduites avec le commerce ou les voyages ou importées de 

façon intentionnelle pour des raisons diverses. Les nouvelles introductions délibérées 

doivent être évaluées pour le danger qu’elles représentent et les espèces introduites 

uniquement après une analyse de risques et une étude d’impact écologique. Ce rapport 

mentionne les modes d’introduction les plus importants et montre qu’un grand nombre 

d’EEE ont été délibérément introduites. L’utilisation pour le jardinage de plantes 

indigènes et de plantes exotiques non-envahissantes devrait être promue. Une législation 

réglementant le commerce des plantes de la liste noire serait un premier pas dans 

la bonne direction pour réduire l’impact de ces espèces. Cependant, des restrictions 

d’utilisation pour les espèces déjà largement présentes en Suisse ne changeront pas 

grand-chose à la situation, à moins d’éradiquer ou de contrôler les populations déjà 

présentes. Les importations et implantations de poissons exotiques sont régulées par la 

loi fédérale sur la pêche, qui cite les espèces pour lesquelles une autorisation 

d’introduction est nécessaire, et celles dont l’introduction est prohibée. C’est une bonne 

base, bien que la loi pourrait être mieux adaptée à la situation actuelle, comme suggéré 

dans le chapitre relatif aux poissons. Le commerce des animaux d’aquarium et terrarium 

est un autre secteur important qui devrait être mieux régulé pour limiter les lâchers 

d’animaux de compagnie dans la nature. Un problème majeur lié aux EEE est 

que le coût de ces invasions est payé par le public alors que ces introductions sont 

motivées par des intérêts financiers privés. Le développement d’outils économiques 

transférant le coût des EEE aux bénéficiaires des échanges commerciaux impliquant 

ces organismes exotiques est une approche pour l’instant négligée (principe du pollueur-payeur). 

Par exemple, des contributions ou taxes pourraient être imposés aux 

importateurs d’organismes vivants ou de marchandises. La sensibilisation du public est 

également un outil important dans la prévention et la gestion des EEE. Une partie du 

public adhèrerait sans aucun doute aux recommandations s’il était au courant de leur 

importance et de leur raison d’être. 

Les chercheurs et décisionnaires ont également besoin d’un meilleur accès à l’information 

concernant les espèces envahissantes, leur impact et les moyens de lutte. Pour 

limiter l’impact des espèces envahissantes déjà présentes en Suisse, leurs populations 

doivent être gérées, c.-à-d. éradiquées ou contrôlées. Parmi les espèces pouvant être 

éradiquées, on peut citer le cerf sika (Cervus nippon), le mouflon (Ovis orientalis) et la 

tadorne casarca (Tadorna ferruginea) qui, dans le cas contraire, risquent d’élargir leur 

distribution et d’envahir des pays voisins. Un programme national pilote d’éradication 

ou de lutte, par exemple contre une plante de la liste noire, est recommandé comme 

étude de cas. Il est également recommandé de surveiller les populations de certaines 

espèces exotiques pour détecter les hausses soudaines de population pouvant indiquer 

un caractère envahissant. En faisant cela, des programmes de contrôle, ou même 

d’éradication, pourraient être décidés avant que les populations ne deviennent totalement 

ingérables. En accumulant l’information nécessaire à la rédaction de ce rapport, il 

est apparu clairement que trop peu d’information était disponible sur les EEE en

Résumé 21 

Suisse. Il est fortement recommandé d’étudier plus en détails ces espèces, en particulier 

leur impact, afin de démontrer leur importance aux décisionnaires et politiques. 

Les ressources financières étant limitées, il est nécessaire de dicter des priorités dans la 

lutte contre les EEE et d’allouer ces ressources là où elles auront l’impact le plus 

important. Il est nécessaire d’évaluer de manière critique la faisabilité de différentes 

méthodes de lutte, et de cibler en priorité les espèces pour lesquelles il n’y a pas de 

conflit d’intérêt. Par exemple, parmi les plantes de la liste noire, une action contre la 

berce du Caucase, une plante de faible intérêt ornemental et posant de sérieux problèmes 

de santé publique, ne devrait pas susciter d’opposition.


1 > Introduction 

The values of societies and the views on issues such as alien species change over time, 

and today the seriousness of alien species with their detrimental impacts on biodiversity, 

economics and human health is widely accepted and management options for 

invasive alien species (IAS) are sought. In the past people did not have the knowledge 

we have today and took many familiar species with them to new areas they were 

settling. Acclimatization societies were established with the goal of introducing European 

species to the new colonies and the newly discovered species of exotic lands into 

Europe. Thus, people cheered the arrival of the English sparrow in North America. The 

poet William Cullen Bryant wrote in ‘The Old World Sparrow’: 

“A winged settler has taken his place 

With Teutons and men of the Celtic race. 

He has followed their path to our hemisphere; 

The Old World Sparrow at last is here.” 

This report compiles published information about alien species and other information 

from experts in Switzerland and abroad on the alien flora and fauna of Switzerland. 

Species occurring in Europe but not (yet) in Switzerland but known to have invasive 

characteristics are also included in this publication. The fact that they are invasive and 

occur in neighbouring countries puts them on a Watch List for which monitoring 

and/or prevention measures would be advisable. 

Names of scientists who wrote chapters are given at the beginning of each one, but the 

many other people whose help was vital in preparing this report are acknowledged at 

the end of this chapter. 

Availability of lists varies tremendously between taxonomic groups, thus, unfortunately, 

it is not possible to list all the alien species of Switzerland. However, for groups 

that are well known, complete lists could be assembled. For some other groups only 

invasive species are given, and some groups are not covered at all. For these latter 

groups, lists of native species are not even available and the introduced or native status 

of many species discovered in Switzerland cannot be demonstrated with certainty. 

These species are called cryptogenic. It has to be emphasized that a report on the alien 

species of a region can only give a snapshot of the current situation, since more species 

will invade and be introduced as time goes by. As long as knowledge about the diversity 

and distribution of native taxa is incomplete, only invasions of taxonomically 

uncommon or high-impact species will be detected. Invasions of cryptic taxa often go 

unnoticed (Müller and Griebeler, 2002). In conclusion, a consistent approach between 

taxonomic groups is not possible due to gaps in knowledge. The groups are discussed

Résumé 23 

in this report on the basis of the available knowledge, which reflects difficulties in 

monitoring and taxonomy and also the importance of the different groups. 

The taxonomic groups chosen, i.e. vertebrates, insects, crustaceans, arachnids, molluscs, 

other animals, plants and fungi, are the basis of separate chapters presenting lists 

of alien species and additional information about them, Fact Sheets for the invasive 

species, and finally an evaluation of the status, impacts, pathways, control options and 

recommendations for the alien species of each group. The Fact Sheets summarize 

information on the invasive species under the headings taxonomy, description, ecology, 

origin, introduction, distribution, impact, management and references. A special focus 

is given to information on impacts of the species on the environment and economy to 

indicate their detrimental nature and the importance of managing them. This information 

is often difficult to find but crucial to show the true potential threat to Switzerland 

without being hysterical about it. 

All signatories to the Convention on Biological Diversity (CBD), including Switzerland, 

are obliged to prevent the introduction of, control or eradicate those alien species 

which threaten ecosystems, habitats or species. There are other international instruments, 

ratified by Switzerland, calling for management of invasive species, e.g. the 

Convention on the Conservation of Migratory Species of Wild Animals and the Convention 

on the Conservation of European Wildlife and Natural Habitats. This report 

can also be used in response to the call from the CBD Secretariat for countries to 

produce lists of alien species and can provide information for a national strategy on 

IAS. 

The importance of IAS is increasingly recognized in Central Europe, indicated by the 

recently published book Neobiota in Österreich (Essl and Rabitsch, 2002) and the very 

recently produced Gebietsfremde Arten; Positionspapier des Bundesamtes für Naturschutz 

in Germany (Klingenstein et al., 2005). 

The following sections of this chapter explain the definitions used in the report, then 

present a predominantly global perspective of the IAS issue, with examples from 

Switzerland. Evaluations of pathways, origins of the species, number of alien species in 

comparison to native species, their impacts, management options and other trends are 

given in the chapters on the taxonomic groups. An overall evaluation of these factors 

was attempted, but it became obvious that that was not a constructive exercise, since 

the clear trends in some taxonomic groups were diluted and combining groups with 

very different knowledge bases made it difficult to compare the results. However, 

within the groups, trends are often very obvious and for these readers are referred to 

the chapters on the taxonomic groups. 

1.1 Definitions 

Definitions used in relation to IAS are as varied as the species themselves. The term 

‘invasive’, for instance, is used in one extreme, to describe a population that is expand-


ing (invading somewhere) to another, for species which have a negative impact on 

native species, ecosystems and habitats. A set of widely used definitions is provided by 

the Convention on Biological Diversity, available on their websites (see Article 2, Use 

of Terms at: http://www.biodiv.org/convention/articles.asp?lg=0&a+cbd–02 and Annex 2 

of the item 8 at: http://www.biodiv.org/doc/meeting.aspx?mtg=sbstta–06&tab=1). 

As long as the terms are not harmonized, it is crucial to give the definitions used in a 

document. Thus, short definitions used in this report are presented below. In some 

chapters, separate definitions were used for reasons of clarity, and these are given at 

the beginning of the relevant chapters. 

> Introduction: the movement, by direct or indirect human agency, of a species or 

lower taxon into a new area. Indirect agency is, for instance, the building of a canal, 

while direct movement includes deliberate and accidental introductions. This can be 

either within Switzerland or from another country into Switzerland, breaching formerly 

insurmountable barriers for the species. The most obvious natural barriers for 

a species in Switzerland are the Alps between the Ticino and the rest of the country, 

but also the different watersheds, towards the North Sea, the Black Sea and the 

Mediterranean Sea. 

> Deliberate introduction: the purposeful movement by humans of a species into a 

new area. This includes also species introduced into confinement, e.g. aquariums 

and zoos. Thus, the introduction is defined here as the initial movement into a new 

area. They can subsequently escape or be released into the environment. 

> Accidental introduction: a species utilizing humans or human delivery systems as 

vectors. This also includes contaminants and diseases of deliberately introduced 

species. 

> Native species: a species living within its natural range. 

> Alien species: a species introduced outside its natural distribution. 

> Invasive alien species (IAS): an alien species which threatens ecosystems, habitats 

and species. These are addressed under Article 8(h) of the CBD. 

Some species are difficult to handle under these definitions because of a lack of information, 

e.g. it is often not possible to determine whether a European species arrived 

with human help or on its own wings or legs. Thus, these definitions should not be 

treated as cast in stone but are flexibly used for the purpose of this report. 

1.2 Invasive alien species – a global overview 

This report can only give a glimpse of the complex issue of IAS, to set the stage for an 

assessment of their importance. A good place to start browsing through the IAS literature 

is in books published on the topic, e.g. the classic Elton (1958), Drake et al. 

(1989), Di Castri et al. (1990), Williamson (1996), Mooney and Hobbs (2000), Shine et 

al. (2000), Low (2001), McNeely (2001), Wittenberg and Cock (2001), Baskin (2002), 

Kowarik and Starfinger (2002), Leppäkoski et al. (2002), Pimentel (2002), Kowarik 

(2003), Mooney et al. (2005) and others.

Résumé 25 

Changes in distribution of species are a natural phenomenon; ranges expand and retract 

and species colonize new areas outside their natural range by long-distance dispersal, 

for example reptiles on floating wood to new islands. However, these events are rare 

and mostly restricted by natural barriers. The relatively recent globalization of trade 

and travel has inadvertently led to the increased transport of organisms and introduction 

of alien species, tearing down these natural barriers. Alien species are not bad per 

se, in fact many species are used for human consumption, e.g. most crop species are 

aliens in the majority of regions where they are grown. However, some of them may 

subsequently become harmful and pose threats to the environment and human populations. 

IAS are increasingly recognized as one of the major threats to biodiversity. These 

negative effects are best documented in bird extinctions on islands where the majority 

since 1800 have been caused by IAS (BirdLife International, 2000). This global problem 

needs global and local responses, or, even better, proactive measures, and solutions. 

The complexity of the IAS topic stems from the very different species involved, their 

diverse origins, the variety of pathways used, their varied impacts on new environments, 

their relationships with indigenous and other alien species, the ecosystem 

changes caused, their dependence on other factors such as global warming, their human 

dimensions including changes in political and ethical views, and their on-going evolution. 

Invasive alien species are found in virtually every taxonomic group. The following 

examples will attest this statement. 

The West Nile virus causing encephalitis hitched a ride to the New World in an infected 

bird, mosquito or human (Enserink, 1999). 

The bacterium Vibrio cholerae (Pacini), the causal organism of the human disease 

cholera, is a member of brackish water communities and is frequently found in ballast 

water of ships (McCarthy and Khambaty, 1994), by which means some new highly 

virulent strains have been redistributed leading to epidemic outbreaks of cholera. 

Another bacterium, Erwinia amylovora (see Fact Sheet in chapter 9) is a serious threat 

to the fruit industry in Switzerland. 

Some fungal pathogens are amongst the IAS with the most disruptive impacts on 

ecosystems. Some well-known examples include fungi attacking trees, e.g. chestnut 

blight (Cryphonectria parasitica (Murrill) Barr) was introduced with alien chestnut 

trees to North America, where it virtually eradicated the American chestnut (Castanea 

dentata (Marsh.) Borkh.), which was a dominant tree in eastern forests, thereby changing 

the entire ecosystem and composition of the forests (Hendrickson, 2002) and is 

now, albeit with less severity, attacking trees in Switzerland. 

Weeds are another predominant group of IAS known to cause economic problems as 

well as deleterious effects on the environment. The giant reed (Arundo donax L.) is 

used in many countries, for example as windbreaks, and is readily invading natural 

areas; the small herb common ragweed (Ambrosia artemisiifolia L.) is swiftly expand-


ing its exotic range in Europe causing severe allergic problems for the human population. 

Many different kinds of worms found their way to new areas with human assistance, 

especially parasitic worms from the Plathelminthes and Nemathelminthes, for example 

the nematode Anguillicola crassus, which attacks the native eel (Anguilla anguilla L.). 

A spectacular disaster caused by an introduced snail was the introduction of the carnivorous 

rosy wolfsnail (Euglandina rosea (Férussac)) to many subtropical and tropical 

islands destroying the diverse endemic snail faunas. Another example of an introduced 

mollusc in Europe is perhaps the most aggressive freshwater invader worldwide, 

the zebra mussel (Dreissena polymorpha (Pallas)), inflicting not only huge economic 

costs but also severe biotic changes as it functions as an ecosystem engineer species 

(Karateyev et al., 2002). 

Small introduced crustaceans dominate the fauna of many rivers and lakes worldwide 

due to the increased ship traffic that transports organisms in ballast water to new areas, 

and also to the creation of canals connecting formerly insurmountable natural barriers 

between watersheds. Thus, alien species (mainly crustaceans and molluscs) dominate 

the Rhine in total abundance and produce a biomass of more than 80 % (Haas et al., 

2002). 

Interestingly, introduced insects, despite their diversity, have not shown a high potential 

for causing environmental problems, although they can be devastating pests in 

agriculture and forestry. However, several ant species destroy native faunas, especially 

on islands – but also, e.g. the Argentine ant (Linepithema humile (Mayr)), in southern 

Europe. 

The infamous cane toad (Bufo marinus (L.)) is spreading quickly through Australia 

feeding on everything smaller than itself and poisoning the bigger predators, such as 

quolls (Dasyurus spp. E. Geoffroy St.-Hilaire). 

One of the most devastating introduced reptiles is the brown tree snake (Boiga irregularis 

(Merrem)) on Pacific islands; it arrived on Guam on military equipment and 

brought a silent spring to the island by feasting on the bird species. Moreover, it causes 

frequent power cuts and is a danger to babies because of its venom. 

The Nile perch (Lates niloticus (L.)), introduced into Lake Victoria to improve fisheries, 

caused the extinction of more than 100 fish species of the cichlid family; most of 

them endemic to the lake – before the predator came it was called an evolutionary 

laboratory, afterwards an ecological disaster. 

The American ruddy duck (Oxyura jamaicensis (Gmelin)) was introduced to England 

as an addition to the wildfowl fauna, where it ostensibly does no harm, but then it 

spread to Spain where it has swiftly endangered the native close relative, the whiteheaded 

duck (O. leucocephala (Scopoli)) by hybridization.

Résumé 27 

Feral mammals introduced to islands brought many bird species to the brink of extinction 

or beyond by feeding on their eggs and chicks (e.g. Long, 2003). 

However, some taxonomic groups seem to include more invasive species than others 

do. Mammals are a major threat to island faunas and floras. Whereas rats, mongooses, 

mustelids and feral cats devastate the local bird and reptile fauna of islands, feral goats 

(Capra hircus L.) can diminish the native flora drastically. Weeds alter the vegetation 

on many archipelagos to the detriment of the entire ecosystem. Island ecosystems, 

including isolated lakes, are particularly vulnerable to these invaders. However, all 

continents and habitats seem to be vulnerable to invasions, although there appear to be 

some differences between continents. In the highly populated area of Central Europe, 

IAS seem to be of less importance to biodiversity than on other continents with large 

tracts of more natural habitats. The smaller reserves in Central Europe are easier to 

manage and control of alien species in these areas is often more practical. The long 

association between introduced species and the human population in Europe is a very 

different situation compared to other continents, as all habitats are highly altered and 

human-made habitats dominate. These human-made habitats are often regarded as 

valuable heritage in Central Europe and some of them are dominated by alien species 

introduced centuries ago. 

Comparing the numbers of species introduced to species that have established and 

species that have become invasive, one has to bear in mind the long lag phases which 

often occur. Most introduced species take some time before they become invasive, i.e. 

enter the log phase. Kowarik (2003) shows that for woody alien plants in one part of 

Germany, the average time lag between first introduction and expansion is about 147 

years. The occurrence of time lags makes predictions on invasiveness of alien species 

very difficult. A species doing no harm today can still become an invasive of tomorrow, 

especially in combination with other global changes. There are three major factors 

that determine the ability of a species to become invasive: 

1. Intrinsic factors or species traits, such as the ability to adapt to different conditions, a 

wide tolerance of abiotic factors, pre-adaptations to different climatic zones, and a 

high reproductive rate. 

2. Extrinsic factors or relationships between the species and abiotic and biotic factors, 

such as the number of natural enemies, the number of competing species (native and 

alien), other interactions with native and alien species (pollination, dispersal, food 

source, ecosystem engineers), climatic conditions, soil conditions, degree of disturbance 

(natural and human-induced), global climate change, change in land-use patterns, 

and control and eradication of other IAS. 

3. Human dimension. The attractiveness and importance of species to humans influence 

introduction pathways, vectors, the number of specimens introduced, the number 

of introductions, and the potential for eradication or control. 

Predictions about the invasive potential of a species prior to introduction, as now made 

in Australia and New Zealand, remain difficult, despite recent progress in science. The 

best indicator is still whether a species has become invasive in a similar area elsewhere 

(i.e. its invasion history).


1.3 Status of alien species in Switzerland 

As pointed out above, the accelerating pace of movement of people and goods is 

increasing the number of introductions of already established species and new arrivals. 

Therefore lists of alien species cannot be comprehensive, but give only a snapshot of 

the current knowledge. Moreover, the lack of both knowledge and taxonomists for 

some groups precludes lists for such groups being presented. 

The situation regarding IAS in Switzerland is similar to that in other Central European 

countries, in particular Austria, which is also a land-locked country containing part of 

the Alps. Some of the taxonomic sections present numbers of alien species recorded in 

other countries for comparison. A comparison between countries for all taxa cannot be 

given here, since the definitions and criteria used differ considerably between country 

reports and make it impossible to use the figures for comparison with neighbouring 

countries. The different levels of knowledge for the different groups and countries is 

another source of inaccuracy. Some features specific to Switzerland will allow a different 

guild of species to invade. The deep, cold lakes, for example, are probably preventing 

or at least reducing invasions by aquatic weeds that thrive in warm, shallow water. 

This report lists about 800 alien species and describes 107 IAS in Fact Sheets, i.e. five 

mammals, four birds, one reptile, three amphibians, seven fish, four molluscs, 16 

insects, six crustaceans, three spiders, two ‘worms’, seven fungi, one bacteria, and 48 

plants. As mentioned above, some of these species, e.g. the grey squirrel (Sciurus 

carolinensis Gmelin), have not yet entered Switzerland, but their arrival in the near 

future is likely. 

1.4 Pathways 

Pathways can be divided into those for species deliberately introduced and those for 

species accidentally moved around. Examples of species in the first category are 

species used in aquaculture, for fisheries, as forest trees, for agricultural purposes, for 

hunting, and plants used for soil improvement and solely to please humans as ornamentals. 

Most of these can also transport hitchhiking species and people can accidentally 

introduce species on cargo, their boots, etc. To summarize, most aquatics and invertebrates 

in general, are accidental arrivals, whereas most plants and vertebrates are 

deliberately introduced. Minchin and Gollasch (2002) and Carlton and Ruiz (2005) 

give excellent accounts of pathways and vectors in more depth. The latter divide 

pathways into cause (why a species is transported), route (the geographical path) and 

vector (how a species is transported). 

The global trend that vertebrates and plants are mainly deliberately introduced also 

holds true for Switzerland. 75 % (15) of the 20 Black List plants were introduced 

chiefly as ornamentals and 35 of the 37 vertebrates have been deliberately introduced. 

In general, the introduction pathways of species into Europe, rather than into Switzerland, 

have been analysed in this report, since some species arrived in Switzerland by

Résumé 29 

expanding their populations from neighbouring countries. In conclusion, many serious 

invaders were deliberately introduced, often without much incentive beyond the wish 

to colour the landscape, e.g. with ornamental plants and waterfowl. 

Prediction and prevention of new invaders is difficult since trade in species can be 

changed by changing demands. A group not currently a problem may yet become 

problematic in the near future. If, for example, the pet trade in reptiles shifts from 

predominantly tropical and subtropical species to species originating in regions in the 

same latitudes as Europe, such as North America and China, the situation could become 

much worse. 

1.5 Impacts of invasive alien species 

The impacts of IAS are often considerable, in particular where ecosystem functioning 

is being altered or species are being pushed to extinction, as has been shown for many 

bird species. Most extinctions are likely to be caused by a combination of factors and 

are not attributable to a single cause, but there is no doubt that IAS play an important 

role. The environmental impacts can be divided into four major factors: 

> competition, 

> predation (including herbivory), and more subtle interactions such as 

> hybridization and 

> transmission of diseases. 

All these factors alone or in concert with other factors can decrease biodiversity and 

cause extinction. The most obvious examples for competition are between introduced 

and native plants for nutrients and exposure to sunlight. Resource competition has also 

led to the replacement of the native red squirrel (Sciurus vulgaris L.) by the introduced 

American grey squirrel (S. carolinensis) in almost all of Great Britain and it is predicted 

that this trend will continue on the continent. The latter forages more efficiently 

for food and is stronger than the native species (Williamson, 1996). Impacts due to 

predation and herbivory are very extensive on island fauna and flora, as mentioned 

above. The brown tree snake eliminated most of the bird species on Guam, and feral 

goats are a menace to native vegetation on islands, where they were often released as a 

living food resource. A well-known example of hybridization from Europe is the ruddy 

duck, which hybridizes with the native white-headed duck, as mentioned above. In 

some cases IAS can harbour diseases and act as a vector for those diseases to native 

species. This is the case with American introduced crayfish species to Europe, which 

are almost asymptomatic carriers of the crayfish plague (Aphanomyces astaci Schikora), 

but the native noble crayfish (Astacus astacus (L.)) is highly susceptible to the 

disease, and thus is struggling to coexist with populations of the American crayfish 

species. Introduced species can interact with natives in a variety of ways and indirect 

effects can be very difficult to demonstrate. Direct and indirect effects can lead to very 

complex interactions and a combination of effects can cause complex impacts.


In addition to impacts on biodiversity, many IAS impose enormous economic costs. 

These costs can arise through direct losses of agricultural and forestry products and 

through increased production costs associated with control measures (US Congress, 

1993; Pimentel et al., 2000). One often-cited example is the costs inflicted on water 

plants by the zebra mussel, which clogs water pipes and other structures in the Great 

Lakes in North America. Costs for environmental problems are more difficult to calculate 

than costs imposed in the agricultural and other economic sectors. A North American 

study calculated costs of US$ 138 billion per annum to the USA from IAS (Pimentel 

et al., 2000). Some of the costs given in this paper are estimates rather than actual, 

however, even give or take an order of magnitude, it is still an enormous figure and 

shows the importance of IAS. A recently released report (Sinden et al., 2004) estimates 

that weeds are costing agriculture in Australia about Aus$ 4 billion a year, around 20 % 

of which is borne by the consumer, the other 80 % by the producer. According to this 

report, costs associated with lost production and controlling weeds are equivalent to 

0.5 % of gross domestic product, or 14 % of the value of agricultural production in 

Australia. The Aus$ 4 billion estimate is conservative, as it does not include the impact 

on the natural environment, the effect of pollen from the weeds on human health, and 

the cost of volunteer weed control. It also hides the combined Aus$ 1.8 billion cost to 

the economy of salinity and soil acidity. The amount spent on weed control rose by 

Aus$ 68,000 for each additional native plant that was threatened by the invasive weeds. 

Weed control in natural environments cost about Aus$ 20 million in the year from mid 

2001 to mid 2002. Turning to Europe, the costs of Heracleum mantegazzianum Sommier 

et Levier (giant hogweed) in Germany are estimated at € 10 million; € 1 million 

each to the environment and health sectors, and the remainder represents costs to the 

economy. 

Some IAS also have implications for human health. Giant hogweed was introduced 

from the Caucasus to Europe as an ornamental plant. It produces copious amounts of a 

sap containing phototoxic substances (furanocoumarins), which can lead to severe 

burns to the skin. Regularly children, in particular, are hospitalized after contact with 

the plant, especially when they have been playing with the hollow stems and petioles, 

using them as ‘peashooters’. The raccoon dog (Nyctereutes procyonoides Gray), introduced 

as a fur animal, can, like the native red fox (Vulpes vulpes (L.)), act as a vector 

of the most dangerous parasitic disease vectored by mammals to humans in Central 

Europe, i.e. the fox tapeworm (Echinococcus multilocularis Leuckart) (Thiess et al., 

2001). Although the raccoon dog is only an additional vector, this can have effects on 

the population dynamics of the parasite and lead to an increase in the disease in humans. 

Known impacts of species introduced into Switzerland are presented in the chapters on 

the taxonomic groups and their Fact Sheets. Some recent invaders are without demonstrated 

impact in Switzerland; in these cases impacts assessed in other countries are 

given. These provide a glimpse of the possible future. An example is Procambarus 

clarkii Girard (an American crayfish species) which has caused considerable economic 

losses in Italy (Gherardi et al., 1999). Demonstration of impacts is often difficult 

because of the complexity of ecosystems, but alien species occurring in high numbers, 

such as Reynoutria japonica Houtt. (Japanese knotweed) totally covering the banks of

Résumé 31 

a stream in a valley, or an animal biomass of alien species of up to 95 % in the Rhine 

near Basel, must have impacts on the native ecosystem. All species use resources and 

are resources to other creatures and so they alter the web and nutrient flow of the 

ecosystems they are living in. 

1.6 Discussion 

This report compiles the available information about IAS in Switzerland. During the 

compilation it became clear that it is impossible to list all alien organisms, for the 

simple reason that there is a gap in taxonomic knowledge, not only in Switzerland, but 

Europe and the world, reflecting a need for more taxonomic work. There are probably 

more than ten times the species described so far actually existing right now on the 

planet, and for the species that have been described we often know little more than 

their names. This gives a good indication that there will be more species of both native 

and alien origin found in Switzerland in the years to come. Since all knowledge and 

management are based on the concept of ‘species’, it seems obvious that taxonomic 

work is crucial. 

Despite the widespread view that IAS are of less concern in Central Europe than on 

other continents (and more especially on islands) for various reasons, including the 

small size of nature reserves and the high human impact on all ‘natural’ environments, 

and the long association of alien species and humans leading to adaptation, however, 

the number of cases of dramatic impacts is increasing and the awareness among scientists 

and the public is steadily evolving. Thus, the threats from IAS should not be 

underrated. One of the major consequences, which is undoubtedly unfolding before our 

eyes, is global homogenization (catchily called McDonaldization), with the unique 

character of places such as Switzerland being lost, the characteristic flora and fauna 

invaded by organisms which often accomplish to form the largest biomasses in certain 

ecosystems. This is fact and cannot be argued about, while confirmation of impacts is 

difficult to obtain and can be controversial. The concept of ‘bad species’ and ‘good 

species’ in our ecosystems is a rather anthropomorphic view. Even if a population of a 

native species is enhanced, it is not necessarily good for the ecosystem but can disturb 

the natural balances and nutrient and energy flows in the ecosystem. After an era of 

exploitation, it is now time to address global warming and global swarming. 

IAS should not be seen as a specific topic but rather as a part of conservation, trade, 

and other activities. The main question to be answered is not how to deal with IAS, but 

what should Switzerland look like, what are the goals for conservation, what should a 

particular nature reserve or the national park look like? These goals need to be set and 

IAS management will be part of this bigger picture to conserve and reinstate the unique 

ecosystems and habitats of Switzerland. The intact ecosystems can deliver ecosystem 

services in a sustainable manner.


1.7 Recommendations 

This section gives some important advice and recommendations, which emerged while 

compiling the report. Recommendations for groups of invasives and specific species 

are given in more detail in the respective chapters and Fact Sheets. 

Preparing a national strategy against IAS is recommended to deal with IAS in an 

appropriate way and as demanded by the CBD. This action plan should identify the 

agency responsible for assessing the risks posed by introductions, provide funding 

mechanisms and technical advice and support for control options. This is necessary not 

only to fulfil international commitments, but also to protect Switzerland’s ecosystems 

from the detrimental effects of future invasions. 

Prevention measures against further bioinvasions need to be put in place to stem the 

tide of incoming new species arriving accidentally with trade and travel or introduced 

deliberately for various purposes. New deliberate introductions must be assessed as to 

the threat they may present and only introduced on the basis of a risk analysis and 

environmental impact assessment. Scrutinizing imported goods can minimize accidental 

invasions. The report indicates some important pathways for consideration. Most of 

the known invasive species, apart from insects, are deliberately introduced, in particular 

as ornamentals and for fishing or hunting. The use of native plants and non-invasive 

alien plants for gardening should be promoted. Every meadow ploughed, pond filled, 

or forest cut for roads, homes or industrial zones leaves less space for the native flora 

and fauna. Gardens and parks supporting native plants could be a great boost for native 

biodiversity. 

Laws regulating trade in plant species on the Black List would be a first step in the 

right direction to reduce the impact of these species on the environment, economics 

and human health. However, restrictions for species already widely distributed within 

Switzerland will not drastically change the situation unless the populations already 

present are eradicated or controlled. Arrivals of new species with potential for being 

invasive need to be targeted well before they secure a beachhead and become unmanageable. 

Fish introductions are regulated by the Fisheries Act, which names species for 

which an authorization for release is needed and species for which release is prohibited 

altogether. This is a good basis, although the law could be better adapted to the current 

situation. This is described in the chapter on fish. The aquarium and terrarium trade is 

another important sector that could be more strictly regulated to stop releases of pets 

into the wild. With the increasing prohibition of the red-eared slider (Trachemys 

scripta Seidel) in Europe, other species will probably replace it in the pet trade. These 

species are not regulated and, if they are from a more temperate region, they would be 

of even more concern than the red-eared slider. 

A major problem with introductions of IAS is that the costs when they establish and 

become invasive are borne by the public, while the financial incentives for introducing 

them lie with individuals or specific businesses. Development of economic tools that 

shift the burden of IAS to those who benefit from international trade and travel is a 

neglected approach. This is also called the ‘polluter pays’ principle. Appropriate tools

Résumé 33 

would be fees and taxes, including fees levied on those who import the organisms or 

goods. The money raised can be used for prevention and management of IAS. 

Awareness raising is a significant tool in the prevention and management of IAS, since 

some people would adhere to advice if they knew about its importance and the reason 

for it, e.g. ‘freeing’ of pets into the environment. Scientists and decision-makers also 

need better access to information about invasive species, their impacts, and management 

options. This lack of organization of information can be addressed by databases 

or global compendia. This report is a basis for collating information on published 

eradication and management methods for harmful species occurring in Switzerland 

(including key contacts). 

Some key invasive groups to watch for in the future are plants, vertebrates, diseases 

and some invertebrates, as the most invasive species belong to these groups. Introductions 

of crayfish species, for instance, should be regulated; thus the European native 

species are of concern, although so far most attention is focussed on the American 


To address the impacts of some invasive species already present in Switzerland, their 

populations need to be managed: either eradicated or controlled. 

Monitoring for populations of some alien species is recommended to detect any sudden 

explosion in their populations and to watch for their potential invasiveness. By doing 

this, control or even eradication efforts can be employed before the populations become 

unmanageable. In most cases, the transition from a ‘sleeper’ species to an invasive 

species will go undetected without vigilant monitoring. 

Despite the efforts in this report to document impacts of alien species which have 

invasive characteristics, much information is still needed to assess the different impacts, 

direct and indirect, to the native biodiversity. More studies on alien species are 

highly recommended to ascertain the importance of IAS and to demonstrate their 

significance to policy-makers and politicians. 

The first Swiss-wide efforts to combat the populations of selected IAS are recommended. 

The most efficient control options need to be explored and implemented. 

Some species of high concern, such as giant hogweed, seem to be good targets for 

eradication campaigns throughout Switzerland. Populations of giant hogweed are 

currently exploding all over Europe (see, e.g., Kowarik (2003) for Germany and Czech 

Republic), they cause direct harm to people, and successful eradication has been 

achieved using mechanical and chemical control. 

Priority setting is always difficult. The limited resources need to be spent where they 

have the greatest impact in combating IAS. Important points, for example, are to 

consider the feasibility of an approach (will the goal be reached?) and to target species 

with no conflict of interest. Opposition to action against less-important ornamentals on 

the Black List and species of direct human health concern (giant hogweed) will be 

negligible. Other possible targets for eradication are a deer species (sika deer – Cervus 

nippon Temminck) or the mouflon (Ovis orientalis Gmelin), both species with a weak 

lobby.


1.8 Acknowledgements 

We would like to thank Sarah Brunel, Serge Buholzer, Laura Celesti-Grapow, Joao 

Domingues de Almeida, Helena Freitas, Jacques Maillet, Stefan Toepfer, Eduardo 

Sobrino Vesperinas, Gerhard Baechli, Hannes Bauer, Claude Besuchet, Wolfgang 

Billen, Rudolf Bryner, Daniel Burckhardt, Anne Freitag, Yves Gonseth, Jean-Paul 

Haenni, Bernhard Merz, Ladislaus Reser, Bernhard Seifert, Uwe Starfinger, Petr 

Pyšek, Baz Hughes, Ulrike Doyle, Simon Capt and Annette Otte for providing information 

on alien species in Europe and their help in the compilation of the list of alien 

species in Switzerland, as well as many more Swiss and European colleagues who 

helped us by sending reprints or giving advice. We are grateful to the Swiss Commission 

for Wild Plant Conservation (CPS-SKEW) group for their information on invasive 

species in Switzerland. The work on alien insects by Marc Kenis was partially supported 

by the ALARM project (EU 6 th Framework Programme – No. 506675). We 

thank also Tanja Reinhold, Beate Kiefer, Myriam Poll and Ghislaine Cortat for compiling 

information and the literature and Matthew Cock, Kurt Grossenbacher, Daniel 

Hefti, Robert Cowie, Christoph Vorburger, Christoph Scheidegger, Rudolf Müller, 

Piero Genovesi, Francis Cordillot, Harry Evans and Rebecca Murphy who greatly 

improved earlier drafts with their invaluable comments. Finally, we want to express 

deep appreciation to Hans Hosbach from the Bundesamt für Umwelt, Wald und Landschaft 

(BUWAL) for his immense help and financial support to prepare this report.

1 > Introduction 35 

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2 > Vertebrates – Vertebrata 

Prepared by Rüdiger Wittenberg 

All the Fact Sheets for vertebrates have been placed at the end of this chapter. They are 

presented in alphabetical order to make individual ones easier to locate, not in taxonomical 

sequence as in the text and lists below. 

2.1 Mammals – Mammalia 

There are currently about eight mammalian neozoa with established populations in 

Switzerland (Table 2.1), another species (coypu) is irregularly found, and the grey 

squirrel is discussed as a threat to Switzerland. Of the established species, one is greatly 

reduced in numbers (European rabbit) due to unfavourable climatic conditions, 

hunting, and introduced diseases such as myxomatosis and rabbit haemorrhagic disease 

(RHD) (see below). Three have only small, localized populations (Siberian chipmunk, 

sika deer, mouflon), one is currently in the process of invasion (raccoon dog), two are 

well-established and spreading through Switzerland (raccoon, musk rat) and one is 

abundant (brown rat). 

The European rabbit (Oryctolagus cuniculus L.) was widely distributed throughout 

Central and Southern Europe before the last glacial period (Kaetzke et al., 2003). 

During this period the distribution retracted dramatically and the European rabbit 

survived only on the Iberian Peninsula. Later it was distributed by humans, because it 

was prized for its meat, first along the Mediterranean Sea coast and then to Central 

Europe. However, it arrived relatively recently in Switzerland, where it was locally 

introduced in the 19 th century (Long, 2003). The distribution in Switzerland was always 

very patchy in lowlands around Basel, Genève and in the Valais and Ticino 

(Hausser, 1995) with a decreasing trend in its population sizes. While the European 

rabbit was able to adapt very well to the hot and arid interior of Australia, it suffers 

under cold winter temperatures and is restricted by the depth of the snow which covers 

its food (Flux, 1994). The small population of the European rabbit in Switzerland and 

the very few suitable habitats render this alien species unimportant. This is an interesting 

contrast to many other countries around the globe where the species is recognized 

for its detrimental effects on agriculture, forestry and the environment, including the 

more than 800 islands where it has been introduced. It should be noted that releases of 

other alien members of the family Leporidae should be discouraged. A North American 

species introduced for hunting at several locations in Europe, including Switzerland, 

France and Italy is Sylvilagus floridanus (J.A. Allan). The main concern is the possibility 

of transmission of diseases to native species, e.g. myxomatosis and RHD.

2 > Vertebrates – Vertebrata 37 

The only introduced squirrel is the Siberian chipmunk (Tamias sibiricus (Laxmann)). 

It was released into parks in Genève by pet lovers and established a small but stable 

population (Long, 2003). Its native distribution covers a large part of northern Asia and 

it is expanding its range westwards, and arrived in Finland in recent years (Grzimek, 

1975). This small beautiful squirrel is frequently kept as a pet and has escaped or been 

deliberately introduced in several European countries. In Switzerland only one small 

colony is known, but it has also established populations in Freiburg im Breisgau in 

Germany and in Italy (Personal observation; Andreotti et al., 2001). In Russia it is 

known to destroy half the average forest nut production and cause great damage to 

grain crops. Since the chipmunks mainly feed on the ground, they can severely affect 

crops and also damage gardens and orchards (Long, 2003). A Belgian study, which 

compared the abundance of birds in areas with and without the alien squirrel, concluded 

that T. sibiricus has no impact on bird populations (Riegel, 2001). In most of 

Europe, released populations have not increased and spread significantly, and it seems 

that the Siberian chipmunk is dependent on a rich food source, as it is most often found 

in parks and graveyards with a variety of different plant species (Krapp, 1978a, b). 

Thus, it should be regarded as a species with a low invasion potential. However, the 

release of pet animals should be of great concern and should probably be better regulated. 

In particular, the danger of diseases carried by alien pets to wildlife, other pets 

and humans should not be underrated, as demonstrated by the recent arrival of diseases 

with introduced pet rats from Africa to the USA. 

Another squirrel species, although one that has not yet arrived in Switzerland, is of 

great concern, as it is established in Italy and spreading. The grey squirrel (Sciurus 

carolinensis Gmelin) (see Fact Sheet) is one of the rare cases where the impact on a 

native congeneric species, i.e. the red squirrel (Sciurus vulgaris L.), is well documented. 

In Great Britain, except for some mountainous conifer forests, the red squirrel 

has been replaced completely by the grey squirrel. Today, the population in northern 

Italy is rapidly expanding its range and threatens to invade Switzerland in the next 20 

years or so. Swiss authorities should follow the expansion closely and put prevention 

methods in place to stop or delay the spread at the border. Whereas the invasion into 

the Ticino is more imminent, the modelled expansion of the grey squirrel to France is 

of greater concern, as from here it can expand into Switzerland around Genève. Moreover, 

if isolated populations outside the invasion front are encountered, they should be 

eradicated as long as they are small. Swiss authorities should also initiate discussion 

with Italian authorities to implement the approved action plan to eradicate the species 

in the Italian part of the Ticino valley. 

The re-introduction of beavers in some countries has been problematic in the past. In 

some areas, at least in Austria and Finland and perhaps Germany (Geiter et al., 2002), 

the American congeneric Castor canadensis Kuhl was introduced instead of the European 

beaver (C. fiber L.) (Freye, 1978; Englisch, 2002). These two species are very 

similar and indeed were considered to be one species until recently, but the karyotypes 

differ. No further introductions of the American species should be made in Europe. The 

introductions of C. fiber of different origins within Europe seem to be of less concern 

in many parts, since the species is genetically relatively uniform, with only a few


obvious subspecies. In general, specimens used for re-introductions should come from 

the same subspecies or populations, original to the specific area, whenever possible. 

The North American muskrat (Ondatra zibethicus (L.)) (see Fact Sheet) showed a 

tremendous expansion of its range in Europe in the 100 years after its first introduction 

to Prague (Elton, 1958). A discussion of the process of the spread is given by Williamson 

(1996). The invasion front is moving swiftly southwards in Switzerland. It has the 

potential to colonize all aquatic bodies in the lowland parts of Switzerland. The damage 

to waterways and the costs to control this species are enormous (Reinhardt et al., 

2003). However, given the severity of the damage and the negative impact on native 

mussels (Unionidae) through predation, an eradication or control programme should be 

considered. Options should be explored together with neighbouring countries, e.g. 

Germany. Eradication is probably not achievable given the large population already 

present in Switzerland and the existence of sources for new invasions in Germany and 

France. On the British Isle the muskrat was eradicated in 1939, but the population was 

still small and confined to several centres of introduction in England, Scotland and 

Ireland. The British Isles are not connected to continental Europe, thus it is easier to 

prevent re-infestation. It has also been suggested that the UK climate is not ideal for 

the species, so that eradication was more easily achieved. 

Another large rodent, the coypu (Myocastor coypus (Molina)) has been found in 

Switzerland on several occasions and in different areas, mainly in the north-west 

(Hausser, 1995). Its origin is the southern half of South America and it is confined to 

water edges. Like the muskrat, it was deliberately introduced into the wild for hunting 

because of its fur; like most aquatic animals, it has very dense fur to help it conserve 

heat in cold water. However, most coypu colonies are derived from animals that escaped 

from fur farms and established short-lived populations in Central Europe. They 

are not well-adapted to cold winters, thus severe winters often cause high mortality and 

local extinction. In the Mediterranean area (e.g. southern France and northern Italy) 

coypu populations thrive and they damage dams by burrowing and reduce crop yields 

(Southern, 1964). It can be concluded that the coypu is unlikely to establish permanent 

populations and cause an environmental impact in Switzerland, because of the prolonged 

frost periods. Most of the sightings will be of single specimens or temporary 

populations. However, it needs to be stressed that it is difficult to be confident about 

this prediction. The coypu was successfully eradicated from England, and casualties 

amongst non-target organisms, which had been considerable during the muskrat eradication, 

were reduced by using cage traps and releasing non-target species back into the 

wild (Williamson, 1996). 

The ubiquitous brown rat (Rattus norvegicus (Berkenhout)) (see Fact Sheet) is a 

species that adapted very well to human environments. The origin of the genus Rattus 

is the warm climate of South-east Asia, but R. norvegicus is from the northern part of 

the distribution, and is thus better adapted to a cold climate. However, it is surprising 

how well this species spread with humans all around the globe. Its omnivorous character, 

together with its ability to live in close vicinity to humans, led to its success. The 

recorded impacts from this rodent are considerable. Its negative impact on the environment 

is mainly evident on islands, where it has even caused bird extinctions. In


urban areas, the normal habitat in Central Europe, the environmental impact is probably 

less pronounced, although it is an additional omnivorous predator. However, its 

impact on structures and foodstuffs and its role as a disease vector in human settlements 

are unambiguous and the brown rat is controlled in many cities. 

The raccoon (Procyon lotor (L.)) (see Fact Sheet) is the only member of the family 

Procyonidae introduced to Europe. It was introduced from North America and released 

in Germany in 1934. From that and other subsequent releases, it spread through Germany 

and reached Switzerland in 1976. The spread continues and it will eventually 

inhabit the lowland parts of Switzerland to Genève in the south and the Valais. The 

impact of the species is disputed. A definitive conclusion cannot be reached without 

studies being carried out in Switzerland to assess its impact on the native wildlife and 

as a vector of diseases (Hohmann et al., 2002). This addition to the native fauna may 

have to be accepted, since control measures are not very effective and its impacts have 

not (yet) been demontrated. If incidences of diseases carried by the raccoon increase, 

hunters will have to focus more on this species. 

The only introduced dog (Canidae) in Central Europe is the east Asian raccoon dog 

(Nyctereutes procyonoides (Gray)) (see Fact Sheet), which was for decades and at 

many places in the former USSR extensively released as a fur animal. The acclimatization 

of the species and the value of the fur are questionable. However, it spread westwards 

and recently reached France. Incorrect identification based on field observations 

by laypeople may be frequent, because they are not familiar with this species and it can 

be confused with other predators, such as the raccoon. Thus, identification of dead 

animals is the most reliable way of evaluating its spread through Europe. Opinions 

about its impact vary between it being a benign species and a species causing severe 

impact on native wildlife. One argument is that, as a generalist on abundant food 

resources, it does no harm to rare organisms. Others argue that predation on bird 

species and amphibians might have a negative impact (Kauhala, 1996). The status of 

many amphibians as endangered in Central Europe and the fact that amphibians were 

found in proportions of up to 45 % in the diet of the raccoon dog (Barbu, 1972) indicates 

the potential harm. It also plays a role as a vector of diseases to humans and other 

predators (Weidema, 2000). It is recommended that the spread of the raccoon dog 

should be monitored and its impact in Switzerland evaluated. However, a control 

programme seems unlikely to achieve success, because of the raccoon dog’s secretive 

behaviour and its continuing invasion from the East. The raccoon dog and the raccoon 

are two additional predators with which native animals have to cope. Thus, although 

the impacts of the introduced predatory species are not so different from those of native 

origin, if they add to the total predator load, they are likely increase the predatory 

pressure, and destabilize existing populations and population cycles. 

The only established alien deer (Cervidae) in Switzerland is the sika deer (Cervus 

nippon Temminck). It is a fairly small deer species, intermediate in size between the 

native roe deer (Capreolus capreolus (L.)) and red deer (Cervus elaphus L.). The 

summer coat is chestnut brown to buff brown with white spots, while it is uniform 

grey-brown during winter. The rump patch is white with a black upper border and the 

white tail has a black stripe. The typical antlers have four points each. The sika deer is


mostly nocturnal, although this might be an adaptation to disturbance and hunting, 

since most deer species, if undisturbed, would probably be diurnal. It was introduced 

from its original range in eastern Asia to several countries in Europe, as well as North 

America, Africa, Madagascar, Australia and New Zealand (Long, 2003), as a game 

animal, for meat, and as a conservation measure. The sika deer in its natural distribution 

range, like most (Asiatic) deer species, is under threat due to high hunting pressure 

and many subspecies are rare (Kurt, 1988). Many sika deer introductions were successful, 

including one in southern Germany, which was the source of the Swiss population. 

The enclosure near Schaffhausen was opened in 1941 and a slowly increasing population 

established (Hausser, 1995). This population is still restricted to the north of the 

river Rhine. The sika deer is a serious forest pest, browsing young trees and also 

removing bark (Welch et al., 2001). Native deer show the same behaviour and their 

large populations have created an unresolved problem in many places. However, an 

additional, alien, deer species can intensify tree damage (Eisfeld and Fischer, 1996). It 

can damage crops, as do other ungulates, and can be a road hazard. A serious threat to 

the native red deer could potentially come from hybridization with the alien sika deer 

(Krapp und Niethammer, 1986; Welch et al., 2001). However, hybridization has not yet 

been demonstrated in Germany or Austria (Geiter et al., 2002; Welch et al., 2001). 

Thus, there is an urgent need to monitor the Swiss population of sika deer and study 

whether hybridization with the red deer occurs. The outcome of the study will be 

important for a decision on how to manage the sika deer population – eradication, 

containment or ‘harvest’ hunting. The other fact to be taken into consideration is the 

status of the endangered populations of sika deer in its native range. A population in 

Switzerland could be valuable for the conservation of the species. A problem with 

many European populations is the lack of knowledge concerning which subspecies 

were introduced, and many are of mixed origins. Thus, given that sika deer is common 

in other introduced areas, the species should preferably be eradicated in Switzerland or 

at least contained in the infested area. 

The mouflon (Ovis orientalis ssp. musimon Gmelin or O. ammon ssp. musimon (Pallas)) 

has established a small population over the last 20 years or so in the Valais, where 

they are slowly increasing in numbers. The mouflon is a member of a species-complex 

of wild sheep. The views on species status in that group vary considerably between 

authors. The mouflon was introduced to Central Europe from Corsica and Sardinia. 

However, the status of these populations is not clear. While some argue that the mouflon 

is native to these islands, Poplin (1979) and others provide evidence that the 

populations on Corsica and Sardinia are descendants from domestic animals that were 

introduced from Asia in the Neolithic Age. The animals were still very similar to their 

wild ancestors when brought to the Mediterranean islands. In about 1980, the mouflon 

entered the Valais from a population in France and established populations in the lower 

Valais. In some localities the mouflon competes with the chamois (Rupicapra rupicapra 

(L.)), but in general the environmental impact will not be significant (Andreotti 

et al., 2001). As long as the population in Switzerland is small, no significant economic 

damage will occur. A decision on the future of the mouflon in Switzerland needs to be 

taken before the populations spread any further. Excluding the game hunting aspect, it 

is an alien species with no value, and today the value of native species is a predominant 

consideration in nature conservation, therefore control of the species could be consid-


ered. It is recommended that the species at least be contained to the present infested 

area, using hunting as a measure of control. 

A list of species presenting a potential threat to native biodiversity is not complete 

without mentioning domestic animals. Cats (Felis catus L.), ferrets (Mustela furo L.), 

dogs (Canis familiaris L.) and goats (Capra hircus L.) are examples of domestic 

animals for which an environmental impact is documented (Long, 2003). As with most 

IAS, the impacts of the above-mentioned domestic animals are greatest on islands, 

however there are demonstrated impacts in Europe. Domestic cats are very efficient 

hunters and will kill wild prey, despite being fed. Based on a survey, the total number 

of mammals, birds, amphibians and reptiles killed by domestic cats in England per year 

has been estimated to exceed 89 million, including 25 million birds (Woods et al., 

2003). Feral cats, which depend entirely on wild food resources, add to this figure. 

Domestic populations can occur at high densities, because they are fed and belong to 

households. Urban and rural habitats, where the domestic cats mainly hunt, do not have 

many endangered species, but are a valuable habitat in highly populated Central Europe. 

Thus, the effect on native biodiversity is significant. However, a management plan 

for domestic cats, such as by-laws to keep cats indoors near nature reserves, is a thorny 

topic. The impact of hybridization with the wild cat (Felis silvestris Schreber) is not 

clear, but it seems to be a conservation issue in some areas (Randi et al., 2001). 

The feral ferret is a domesticated form of the eastern polecat (Mustela putorius L.) and 

escaped animals are widely found. Potentially there could be damage to native small 

mammal and ground-nesting bird populations and from introgression of genes into the 

wild form, but there is very little information about feral ferrets in the wild (e.g. 

whether there are self-sustaining populations). Feral dogs are more of a problem for 

game animals than to biodiversity in Central Europe. Problems with feral goats in 

Central Europe, in contrast to island ecosystems on a global scale, are rare and local 

and limited to hybridization with the native ibex (Capra ibex (L.)). 

About half of the alien mammal species occurring in (or threatening to invade) Switzerland 

(i.e. muskrat, coypu, grey squirrel, sika deer, raccoon and raccoon dog) are 

given as examples of species threatening European wildlife and habitats in the Appendix 

of Recommendation No. 77 (1999) on eradication of non-native terrestrial vertebrates 

of the Bern Convention on the Conservation of European Wildlife and Natural 

Habitats (for details on the recommendation for management, see 

http://www.nature.coe.int/english/main/Bern/texts/rec9977.htm). This recommendation 

was adopted by the Standing Committee and specifies the recommended action to be 

taken against IAS, including monitoring, control of sale, and efficacy of eradication 

efforts. The recommendation sets another framework for dealing with IAS in Europe. 

Despite the low number of mammalian neozoa, some patterns can be observed and are 

discussed below. The ten species listed above are members of nine families. Two of 

these families have no native members in Europe: Capromyidae occur only in the New 

World, and Procyonidae in either the New World and east Asia or exclusively in the 

New World, depending on whether the red panda, Ailurus fulgens (Cuvier), is included 

or not. The different phylogenetic origin of the ten species is reflected in the very


different biologies of the species, which include small rodents, large herbivores and 

carnivores. 

Five species are of Asian origin (four from eastern Asia and one from western Asia), 

four from the New World (one of those from South America), and one is Mediterranean. 

The pathways of their introductions reveal a clear pattern, which is generally true for 

introduced mammals: they were deliberately introduced into Europe. Only one species 

arrived as a stowaway animal in cargo, ships and other vehicles – the ubiquitous brown 

rat. The majority of the species are fur animals which were released and escaped from 

farms (four species); the two large ungulates were released to enrich the hunting fauna, 

one was used as a food resource and the other to enrich the fauna and for aesthetic 

reasons. One other interesting aspect is how the species arrived in Switzerland. The 

pathway analysis presented above shows how the species were transported into Europe. 

Only four of the ten species in Table 2.1 were actually introduced directly into Switzerland. 

The most (potentially) damaging species have spread into Switzerland from an 

introduction elsewhere in Europe, mainly Germany and France. This highlights the 

importance of international dialogue and collaboration on IAS issues. 

Some of the most destructive alien species on a global scale are mammals (Long, 

2003). Although the number of introduced species is fairly small in comparison to 

other groups, the impact is considered to be enormous, especially in island ecosystems. 

The large herbivores cause a major impact on plants because of their size and the 

amount they eat, while small carnivores (e.g. Mustelidae) and omnivorous mammals 

(e.g. Muridae) are intelligent and adaptable species, which are able to prey on a varied 

diet and can thrive in close proximity to humans. The latter trait facilitates their wide 

spread by human-mediated transport. The potential impacts of mammalian neozoa in 

Switzerland are discussed in the species descriptions and the Fact Sheets. Fact Sheets 

are provided for the five species which are likely to cause some impact. There is no 

obvious general pattern, besides the fact that the small mammals have had the highest 

impact through predation on native species and damage to human constructions, including 

waterways. The date of introduction and perceived impact show no correlation, 

since the potential for impact rather than the actual impact in Switzerland is used. 

Thus, the grey squirrel, which has not yet been found in Switzerland, is one of the 

species of concern. On the other hand, the two species introduced in the 19 th century 

comprise one highly damaging species and one which is now almost extinct. 

The small number of introduced species means that general patterns observed in larger 

data pools are unlikely to be replicated, due to chance. 

There are about 86 mammal species currently reproducing in Switzerland, of which 

nine are neozoa (coypu included), thus about 10 % are introduced. When the list of species 

is compared to those of the neighbouring countries Austria and Germany, there is a 

high overlap in species composition (Englisch, 2002; Geiter et al., 2002). The total 

number is a little smaller (Austria: 11; Germany: 11); the most obvious difference is 

the absence of fallow deer (Cervus dama (L.)) and mink (Mustela vison Schreber), both


established in the other two countries. Gibb and Flux (1973) list twice as many introduced 

mammals to New Zealand, i.e. 25, and the damage they cause is enormous, since 

the islands had only two native mammal species (both bats). The niches occupied elsewhere 

by terrestrial mammals were occupied in New Zealand by native bird species. 

The management options for the species are discussed in the text on individual species, 

above. The invasive or potentially invasive species are very difficult targets for eradication 

and control. The same traits that make them successful in the invasion process 

renders them difficult to control, e.g. adaptability and a high fecundity. 

Tab. 2.1 > Established alien mammals in Switzerland. 

Scientific name 

Oryctolagus cuniculus 

(L., 1758) 

Tamias sibiricus 

(Laxmann, 1769) 

Sciurus carolinensis 

Gmelin, 1788 

Ondatra zibethicus 

(L., 1766) 

Myocastor coypus 

(Molina, 1782) 

Rattus norvegicus 

(Berkenhout, 1769) 

Procyon lotor 

(L. 1758) 

Nyctereutes procyonoides 

Gray, 1834 

Cervus nippon 

Temminck, 1836 

Ovis orientalis 

musimon Gmelin, 

1774 

Family Origin Year Pathway Impact Note 

Leporidae Iberian Peninsula 19th century 

Sciuridae Asian 1975? Escaped and released to 

establish population 

from pet lovers 

Sciuridae Eastern North 

America 

Released for food Alteration of plant succession 

Agricultural pest 

- Released for aesthetic 

reasons 

Arvicolidae North America 1935 Escaped from fur farms 

and released to provide 

wild fur harvest 

Capromyidae South America - Escaped from fur farms 

and released to provide 

wild fur harvest 

Muridae Southeast Russia 

and northern China 

Procyonidae North and Central 

America 

19 th 

century 

Transported inadvertently 

in ships and other 

vehicles 

1976 Releases as a fur animal 

and to enrich the fauna 

Escapees from captivity 

Canidae East Asia 2003 Acclimatization as a fur 

animal 

Cervidae South-eastern 

Russia, eastern 

China, Japan and 

Korea 

1941 Released for sport 

hunting and for conservation 

of the species 

Bovidae Western Asia 1985? Released as a game 

animal 

Great damage to grain crops and forest 

nut production in its native area 

Replaces the native red squirrel 

Stripping bark of trees can cause 

damage in plantations 

Dramatic economic costs due to 

damage to waterways 

Predation on native mussel populations 

Damage to crops by feeding and water 

banks by burrowing 

Transmission of human diseases 

High control costs 

Damage to crops and structures 

Predator of invertebrates and vertebrates, 

with a possible impact through 

bird nest predation 

Nuisance in urban areas 

Problem in orchards? 

Vector of diseases 

Predator of vertebrates 

Vector of diseases 

Serious forest pest 

Hybridization with red deer (everywhere?) 

The species does not 

thrive in Switzerland 

due to the cold winters 

Only small local 

population in parks in 

Genève 

This species is not yet 

found in Switzerland, 

but is rapidly spreading 

in Italy 

Effective control 

options should be 

considered 

A permanent establishment 

seems 

unlikely because of 

harsh winters 

Generally, urban 

populations are 

controlled 

It will spread through 

the entire Mittelland 

within the next few 

years/decades 

It is only currently 

spreading into 

Switzerland from 

Germany and France 

Only one restricted 

population in Switzerland 

Local competition with chamois Only a small population 

in the lower Valais


2.2 Birds – Aves 

About a quarter of the 510 bird species recorded for Switzerland are alien. This is not 

surprising, since most birds are good flyers and many migrate regularly. The latter can 

easily go astray, especially during freak weather events. Hurricane ‘Lothar’, for example, 

was responsible for the accidental occurrence of a pelagic bird (generally found far 

out at sea), the European storm-petrel (Hydrobates pelagicus (L.)), in land-locked 

Switzerland (Keller and Zbinden, 2001). About 200 species breed regularly in Switzerland. 

Some bird species are spreading naturally through Europe and into Switzerland. They 

are not included in the list, although their spread might be triggered by human alterations 

to the landscape. The spread of these species is indirectly facilitated by human 

action, but they are not alien as defined here. The collared dove (Streptopelia decaocto 

(Frivaldszky)) has spread phenomenally from the Balkans north-west through most of 

Europe (Glutz von Blotzheim, 1980). Several hypotheses have been put forward to 

account for this spread, including an increased amount of food in rural areas and 

genetic changes in the bird population, but there is no agreement on the explanation. 

The species considered in this report are exclusively those which were released or 

escaped and became established, but not those that expanded their range to include 

Switzerland. However, species escaping from captivity and observed in the wild or 

found to breed irregularly are not included. Thus, the list provided here takes into 

account only birds with established populations in Switzerland or in neighbouring 

countries, from which spread into Switzerland can be reasonably expected. 

Firstly, bird species with established populations in Switzerland (six species) are 

discussed, and secondly, alien species established in nearby countries which have the 

potential to spread to Switzerland are considered. 

The cormorant (Phalacrocorax carbo L.) is a common guest during winter in Switzerland, 

but the first breeding pairs are now established along the Aare near Bern. The 

birds are probably from the population kept under semi-wild conditions in the zoo. 

Following the banning of hunting in numerous countries, the cormorant is spreading 

again in Europe and in many places the conflict between conservation and fishing 

interests is fervidly debated. Thus, in this specific case and in general, species should 

be held in secure captivity. Bearing in mind recently acquired knowledge about invasive 

bird species and the ease with which some are able to establish, keeping populations 

under semi-wild conditions in zoos and similar facilities is no longer always 

appropriate. In the recent past, zoos have increased this kind of open confinement to 

simulate a more natural situation for the benefit of visitors. Unfortunately, as it creates 

a new pathway for introductions, this approach has to be changed. A similar case is the 

cattle egret (Bubulcus ibis (L.)), which is frequently kept as free-flying populations in 

zoos, and individuals escape occasionally from captivity. Birds of exotic origin kept 

under semi-natural conditions can cause another problem: introgression of genes into 

native populations.


The mute swan (Cygnus olor (Gmelin)) (see Fact Sheet) was released on park ponds in 

the 17 th century and has subsequently spread to all suitable habitats. It has a stable 

population, so only local problems occur, and it is also a popular species with the 

human population, so that control should be limited to public education concerning the 

impact of feeding waterfowl (Schmid et al., 1998). Stopping the feeding of the swans 

will eliminate the high densities of mute swans. The mute swans would then distribute 

themselves more evenly, due to their territoriality based on intraspecific aggression. 

A second member of the Anatidae, the greylag goose (Anser anser (L.)), the wild form 

of the domestic goose, is not native in Switzerland, but has a growing breeding population 

in several places, apparently originating from illegally released specimens (Kestenholz 

and Heer, 2001), although the presence of wild birds that expanded their range 

cannot be ruled out. Greylag geese are native in an area extending from north-western 

to south-eastern Europe. They were probably released to enrich the local avifauna in 

Switzerland. It can be assumed that the populations will grow, without hunting pressure. 

No environmental impact is expected, since the Swiss population is not far from 

the southern border of the natural distribution, but there might be damage to crops and 

droppings on lawns close to lakes could mean the swans are considered a nuisance. 

The ruddy shelduck (Tadorna ferruginea (Pallas)) (see Fact Sheet) is a Central Asian 

and northern African species, which is a favourite asset of waterfowl collections 

throughout Europe for its striking plumage of an almost orange-brown body and a 

whitish head. In many cases the birds are not kept in cages and regularly escape. Some 

isolated breeding pairs are recorded in many countries. However, Switzerland has the 

only viable population of this species in Europe, and it is in the process of building up 

numbers. Its spread to neighbouring countries should be prevented, since if it were to 

cause subsequent damage and environmental impact, Switzerland would have some 

responsibility. Therefore, it is recommended that this unnecessary population should be 

eliminated while it is of manageable size. 

The mandarin duck (Aix galericulata (L.)) (see Fact Sheet) is the only alien duck 

species to have established in large numbers in Europe. As it is one of the most ornate 

waterfowl species, it was and is frequently held on park ponds in Europe, from where it 

escapes into the wild. Its origin is the eastern part of Asia, where populations have been 

dramatically reduced by habitat changes (mainly logging) and over-hunting. Consequently, 

the European populations might be of some importance for the species, especially 

if there is no demonstrated impact. Thus, a strategy for this species in Europe 

might recommend accepting it. 

The native range of the common pheasant (Phasianus colchicus (L.)) covers a large 

part of Asia with about 40 subspecies described. It has been kept in pheasant exhibitions 

for at least a thousand years in Europe (Geiter et al., 2002). However, it is believed 

that it established in the wild much later, perhaps only in the 18 th century, but its 

history cannot be established with certainty, since the numerous releases obscure the 

sustainability of wild populations. It is a favourite game bird all over Europe and 

millions are released every year. Thus naturalized populations are supported by frequent 

releases and are harvested by hunting, e.g. each year up to 20 million are re-


leased and 12 million are shot in the UK (Kestenholz and Heer, 2001). Almost all wild 

populations in Europe seem to be of hybrid origin from several subspecies, because of 

the many releases of different genetic material. Apparently, many wild populations are 

not able to sustain themselves without human help, e.g., by releases and winter feeding. 

Schmid et al. (1998) estimate a population of fewer than 1,000 for Switzerland, mainly 

in the lowland parts. It is recommended that releases of this alien species are stopped, 

so that naturalized populations may dwindle away. 

One domestic species needs to be mentioned in this section, the feral pigeon (Columba 

livia f. domestica L.). It is descended from the rock dove (Columba livia L.), which 

lives on sea-cliffs and in mountains in southern Europe and the UK. The feral pigeon is 

abundant in most cities of Europe and elsewhere because members of the public supplement 

their natural food. Today they are often recognized as a problem species due to 

their faeces altering the colour and destroying the surfaces of old buildings, statues and 

other artificial structures, and for their role in spreading disease. Most control methods 

have not been successful. The main hindrance is feeding, making education of the 

public a crucial aspect of feral pigeon control in cities. 

Species in other European countries which are expanding their range are discussed 

below, as they may enter Switzerland in the near future. 

The most successful avian invader in Europe is the Canada goose (Branta canadensis 

(L.)), following extensive releases and the availability of suitable habitat for this North 

American species throughout Central and northern Europe. It is rapidly increasing its 

population and expanding its range (Delany, 1993). If this spread continues, it is likely 

to invade Switzerland in the near future. While single individuals ahead of an invasion 

front could be eliminated, the spread of the species in Europe could only be addressed 

through an international effort. Competition with native waterfowl has been frequently 

observed (Madsen et al., 1999) and hybridization with greylag goose is of concern in 

countries with native populations of the latter species (Gebhardt, 1996). The growing 

populations of Canada goose are a cause for concern due to damage to crops and faeces 

deposited in parks and on golf ranges (Kestenholz and Heer, 2001). In spring pastures 

they cause damage by grazing, trampling and fouling. Fouling is also responsible for 

eutrophication and associated algal blooms on small, still waters (Welch et al., 2001). 

Another goose species, which in recent times rapidly spread from a nucleus population 

in the Netherlands, is the Egyptian goose (Alopochen aegyptiacus (L.)). Its native 

range is Sub-Saharan Africa, where it is a ubiquitous species. The Egyptian goose was 

already present in captivity in the UK in the 17 th century, and probably around 1967 

some birds escaped confinement in the Netherlands (Bezzel, 1996). If the affected 

countries employ no counter-measures it seems likely that the Egyptian goose will 

eventually spread into Switzerland, but that will take some time, unless further escapes 

occur in or close to Switzerland. Generally, as for other waterfowl, this species should 

be kept in closed cages to minimize escapes. During the breeding season, Egyptian 

geese are very aggressive, and this could have some impact on native waterfowl.


The introduction of North American ruddy duck (Oxyura jamaicensis (Gmelin)) (see 

Fact Sheet) into Europe led to one of the best-known cases of concern about an alien 

species in relation to conservation of a globally threatened native species, i.e. the 

white-headed duck (Oxyura leucocephala Scopoli)), classified as Vulnerable by IUCN 

(the World Conservation Union) (Hughes et al., 1999). The two species readily hybridize 

and it is likely that unless counter-measures are taken the white-headed duck population 

will be completely absorbed. A European action plan for eradication of the 

destructive invader has been set up to safeguard the small populations of white-headed 

duck in the western and eastern Mediterranean. The plan does not cover Asia, but it is 

to be hoped that the ruddy duck will be eradicated in continental Europe and considerably 

reduced in the UK, so that its spread to Asia becomes unlikely. The spread of 

the ruddy duck within the UK and then through Europe was facilitated by the fact that 

it is a migratory species. While the ‘Action Plan for the White-headed Duck’ (Green 

and Hughes, 1996) names eight threats and limiting factors, the introduction of the 

ruddy duck is the only one that is considered critical for its implementation. Tragically 

the white-headed duck population was just recovering in Spain, from a minimum of 22 

birds in 1977 to about 2,700 today due to a conservation programme, but it is now 

being hit by hybridization with the ruddy duck. Over 4,200 ruddy ducks have now been 

shot in the UK, where shooting at large wintering sites is crucial to the success of the 

action plan. Switzerland has endorsed the eradication plans and agreed to take action 

against the ruddy duck within its borders. Shooting of the ruddy duck has to be conducted 

in a co-ordinated way by hunting and conservation authorities. Firstly, the 

correct identity has to be confirmed, since the two Oxyura species can be very similar. 

It is clear from the current situation that ruddy ducks thrive in Europe, build up large 

viable populations, and spread rapidly. Therefore, keeping ruddy ducks in captivity 

needs to be regulated. While the ultimate goal for such a serious problem species is the 

prohibition of keeping them in captivity, an interim measure should be the monitoring 

of all specimens kept and acceptance of collections only in secure facilities. 

In Europe several parrot species frequently escape from captivity and some of those are 

able to establish in the wild under favourable conditions. Most of these colonies are in 

parks in cities, where a rich food source of fruit-bearing trees and bird feeders during 

the harsh winter time together with temperatures on average 2° C above the surrounding 

landscape allow their survival. The climate seems an important factor for these 

species that naturally inhabit lower latidudes. The most common parrot species are the 

rose-ringed parakeet (Psittacula krameri (Scopoli)) and the monk parakeet (Myiopsitta 

monachus (Boddaert)), which have established large colonies in several European 

cities, including some in neighbouring countries: France, Germany, Austria and Italy. 

There are single reports of breeding attempts of both species in Switzerland. They are 

apparently limited to city environments and it is not known whether there is any genetic 

exchange between the colonies in Europe. The colonies are probably isolated and 

will not spread that far. The rose-ringed parakeet nests in tree cavities, so that it will 

compete with native wildlife. The monk parakeet is unusual, building large communal 

nests on trees, buildings and power pylons. In their home ranges both species are 

recognized as agricultural pests. Other parrot species are found irregularly throughout 

Europe. Any parrots encountered in the wild in Switzerland should be captured.


This section, dealing with alien bird species established in Switzerland and those 

species that are established in neighbouring countries and spreading, illustrates the 

varied importance of bird families involved. There are four Anatidae, one Phasianidae 

and one Phalacrocoracidae established. Moreover, three further Anatidae are spreading 

in neighbouring countries and are expected to arrive in Switzerland in the near future. 

In addition, two Psittacidae are well established in cities of neighbouring countries. 

Thus, Anatidae dominate the species list of alien birds currently establishing colonies 

in the wild in Europe. Estimates of the number of established alien bird species in 

Europe vary depending on the author, but for example Kestenholz and Heer (2001) list 

22 species, of which eight belong to the Anatidae and eight to the Phasianidae. In 

conclusion, the Swiss composition of alien birds mirrors the European situation, with 

the exception of having fewer introduced Phasianidae. The latter group has been 

predominantly released in the UK and France as game birds. The six established species 

in Switzerland represent about 3 % of all breeding species (approximately 205). As 

birds are a vagile and migratory group, a comparison of breeding species is obviously 

the best approach to compare native versus alien species. 

The total of six alien bird species established in Switzerland is comparable with neighbouring 

countries (Table 2.2), especially given that Germany is much bigger. Schuster 

(2002) lists five species (three Anatidae, one Phasianidae, one Psittacidae) for Austria. 

Ten alien bird species (six Anatidae, three Phasianidae, one Psittacidae) are found in 

Germany (Geiter et al., 2002). Italy (Andreotti et al., 2001) has about eight species, but 

the taxonomic composition is different with one Anatidae, one Odontophoridae, two 

Phasianidae, two Psittacidae, one Paradoxornithidae and one Estrildidae.


Tab. 2.2 > Alien birds established () in selected countries of Europe. 

Family Species Country 

Germany Austria Switzerland Italy 

Anatidae Aix galericulata (L.) 

Cygnus olor (Gmelin) native 

Branta canadensis (L.) 

Alopochen aegyptiacus (L.) 

Anser cygnoides (L.) 

Anser indicus (Latham) 

Cygnus atratus (Latham) 

Tadorna ferruginea (Pallas) 

Anser anser (L.) native native 

Phasianidae Phasianus colchicus (L.) 

Meleagris gallopavo L. 

Syrmaticus reevesi (Gray) 

Alectoris chukar (Gray) 

Odontophoridae Colinus virginianus (L.) 

Phalacrocoracidae Phalacrocorax carbo L. native native native 

Psittacidae Psittacula krameri (Scopoli) 

Myiopsitta monachus (Boddaert) 

Paradoxornithidae Paradoxornis alphonsianus (Verreaux) 

Estrildidae Amandava amandava (L.) 

After Geiter et al., 2002 (Germany); Schuster, 2002 (Austria); this report (Switzerland); Andreotti et al., 2001 (Italy). 

The composition of established alien birds in Switzerland seems to reflect human 

activities, i.e. the frequency of release of the species, rather than their ecological traits. 

Therefore, an evaluation of what makes a bird species invasive is less informative than 

a discussion of the attractiveness of species to humans. 

Due to the small number of six established species (or 11, if we consider the spreading 

species of neighbouring countries), there is no obvious pattern to their origin. Three of 

the established species are from within Europe, two from Asia, and one from Africa/Asia. 

The year of introduction (i.e. when it was first found established in the wild) varies 

greatly. However, the very recent significant increase of establishment of species of 

Anatidae and Psittacidae, not only in Switzerland but also other European countries, 

gives rise to concern and points to the need to prevent further introductions. 

The pathways of introduction differ greatly between the three main groups, but are 

characteristic for each group. The Anatidae are either released for aesthetic reasons 

(e.g. mute swan) or have escaped from the numerous ornamental waterfowl collections. 

The members of the Phasianidae are released as game birds for hunting. The Psittacidae 

are, of course, escapees from captivity. The success of establishment in all three


groups is based on the support they receive from the human population, since some are 

released and most are fed in the wild (or receive some other human support). 

The environmental and economic impact of established alien birds in Switzerland is 

probably fairly negligible and limited to some local effects. The exception on a European 

scale is the ruddy duck, which is the critical issue for a native globally endangered 

species. The possible and certain impacts are summarized in Table 2.3. 

Birds seem to cause less concern and actual impact on biodiversity, as outlined above, 

than mammals, but their impressive capability for spread underlines the concern about 

both potential future spread and the unsatisfactory level of knowledge for predicting 

spread and impact. The rapid increase in the number of newly introduced bird species 

recorded in recent times and the spread of some older introductions underline the 

urgency of implementing effective strategies to address the issue. 

The pathway analysis indicates where prevention of future introductions will be most 

efficient. The three major pathways identified are listed below, together with measures 

to help close them. 

Escaped birds from captivity (Psittacidae and Anatidae). Measures to prevent escapes 

of alien bird species from captive collections can include strict standards of security for 

aviaries, a register and documented bird monitoring, and penal and administrative 

sanctions in the event of violation. 

Released birds for aesthetic reasons and to enrich the native fauna (Anatidae). Legislation 

to prevent deliberate introductions should be established, or improved and implemented. 

As can be easily seen from the cases of species spreading through Europe 

towards Switzerland, this issue needs to be tackled on a European scale. The international 

conventions are in place and need to be implemented, e.g. Convention on Biological 

Diversity (CBD), Bern Convention, Bonn Convention, Ramsar Convention. It 

should be noted here that the domestic duck can also pose a problem for the wild 

mallard (Anas platyrhynchos (L.)) because of hybridization. These noticeable hybrids 

are most often observed in urban areas, but they should be eliminated in the wild. 

Species released as game birds (Phasianidae). An environmental risk assessment needs 

to be undertaken for all species considered for release in Europe. In the past chukar 

(Alectoris chukar (Gray)) were released in the Alps, including Switzerland. They can 

hybridize with the native rock partridge (Alectoris graeca (Meisner)). The chukar is the 

eastern equivalent of the rock partridge. These releases are unnecessary and pose a 

potential danger to the indigenous rock partridge, which is one of the nine European 

endemic bird species. 

Management options for the species which can cause problems are detailed in the text 

relating to the species and in the Fact Sheets, e.g. ruddy duck and ruddy shelduck 

should be shot.


Four main recommendations are drawn from this compilation: 

> Based on international obligations to safeguard the globally endangered whiteheaded 

duck, the ruddy duck has to be eliminated (shot) whenever it is found in 

Switzerland. Furthermore, the species should not be kept in captivity. 

> Switzerland has a responsibility in relation to the potential spread of the ruddy 

shelduck. It should prevent the spread of the Swiss population and consider eradicating 

it. 

> Birds held in captivity should be monitored closely and escape prevented. Containment 

of birds under semi-wild conditions should be restricted or prohibited. 

> All releases of birds into the wild should be subject to authorization, whereby releases 

of alien species should be avoided and releases of native birds should be made 

using genetic material typical of the region. 

Tab. 2.3 > Established birds (neozoa) in Switzerland and species to watch for (last three species). 

Scientific name Family Origin Year Pathway Impact Note 

Phalacrocorax Phalacro- Europe 2000 Escaped from Breeding colonies destroy trees and First breeding attempts recorded 

carbo L. coracidae captivity other vegetation below trees. 

Impact on fishery heatedly debated. 

Fish farms 

Cygnus olor Anatidae North-eastern 1690 Releases for Decline of submerged aquatic A much-liked species 

(Gmelin) Europe aesthetic reasons vegetation 

Anser anser (L.) Anatidae Parts of 1983 Released as an Probably no environmental impact Wild form of the domestic goose 

Europe enrichment of the 

avifauna 

Damage of crop possible 

Tadorna ferrugi- Anatidae Central Asia 1997 Escaped from Aggressive behaviour towards other CH has responsibility for the only 

nea (Pallas) and northern captivity waterfowl viable population in the introduced 

Africa European range 

Aix galericulata Anatidae East-Asia 1958 Escaped from Competition for tree holes with other Population is small in CH, but other 

(L.) captivity cavity breeding species? European populations expanding 

Phasianus Phasianidae Asia 18th Released as Competition with native game birds? Pheasant densities are mainly detercolchicus 

(L.) cen- game Indirect effects by predator control to mined by the extent of releases 

tury? relieve pheasants from predation 

Branta canadensis Anatidae North America - Released as an Competition with native waterfowl Has not yet reached Switzerland 

(L.) enrichment of the Hybridization with greylag goose 

avifauna Damage to crops 

Droppings can be a nuisance and 

cause eutrophication in water 

Alopochen Anatidae Sub-Saharan - Escaped from Aggressive behaviour towards other Has not yet reached Switzerland 

aegyptiacus (L.) Africa captivity waterfowl 

Oxyura jamaicen- Anatidae North America - Escaped from Hybridization with the globally There is no established population, 

sis (Gmelin) captivity endangered white-headed duck only records of single birds. These 

threatens the extinction of the latter need to be shot under an EU-wide 

species effort.


2.3 Reptiles – Reptilia 

Three snake species have been relocated within Switzerland, from southern locations to 

colder, northern localities. Two of these relocations were very local. The reintroduction 

of the European pond terrapin used alien genetic material. The only alien 

reptile species in Switzerland as a country are aquatic turtles released from aquariums, 

but they seem not to have established populations yet (Table 2.4). 

The case of the Italian wall lizard (Podarcis sicula (Rafinesque-Schmaltz)) in Switzerland 

is rather mysterious (Hofer et al., 2001). It is not known whether the species is 

native or alien nor is it proven that an established population exists at all. Since specimens 

were found along the railway tracks in the Ticino, an accidental introduction 

from Italy seems likely. 

The dice snake (Natrix tessellata (Laurenti)) is one of the most endangered snakes in 

Switzerland, because it is at the north-western limit of its range (thus it is naturally 

rare). It is native to the Ticino, but was released north of the Alps at several lakes 

(Gruschwitz et al., 1999). Although it is rare in Switzerland, it should not be relocated 

to the north of the Alps. At the Lac de Genève, where it now occurs together with 

another rare snake species, the viperine snake (Natrix maura (L.)), it is probably competing 

with the native species for food and habitat, since the two species have a rather 

similar biology, one occurring in south-western Europe and the other in south-eastern 

Europe (Hofer et al., 2001). 

Small populations of the western whip snake (Coluber viridiflavus (Lacépède)) might 

have established at the Neuenburgersee and in the Valais, from specimens collected in 

the Ticino and released in these areas. The impacts of these populations are probably 

negligible and the populations themselves might not persist. Populations of the Aesculapian 

snake (Elaphe longissima (Laurenti)) at the Neuenburgersee and Bieler See 

may have originated in the same way and again have little impact. The latter species 

does seem to be established (Hofer et al., 2001). 

The status of the European pond terrapin (Emys orbicularis (L.)) in Switzerland is 

not yet resolved (Hofer et al., 2001). Some populations might still be native, but there 

were many re-introductions of the species. In most instances the origin of the specimens 

released is not known, but releases of non-native material could lead to genetic 

introgression into possibly surviving native populations. However, this concern remains 

hypothetical because of the lack of knowledge of the status of extant populations. 

The North American red-eared slider (Trachemys scripta (Seidel)) (see Fact Sheet) is 

representative here of a guild of potential IAS – aquatic turtles from several genera. In 

past years, several countries restricted the importation of this species, because of the 

potential threat. However, this merely leads to a shift to other species by the aquarium 

trade. The red-eared slider is still the species most often found in the wild in high 

numbers and many places, although, because of the direct releases in parks etc., the


species is predominantly recorded around agglomerations (Geiger and Waitzmann, 

1996). The red-eared slider is probably not yet established in the wild in Switzerland, 

but this might change through adaptation and future releases of specimens from a more 

northern natural distribution in North America. Reproduction has been repeatedly 

observed in areas of Europe with a Mediterranean climate. However, even without 

reproduction, the populations in certain areas of Switzerland are extremely high owing 

to frequent releases and the longevity of the species. Therefore there is the potential for 

native biodiversity to be affected, even if reproduction fails. A recent study by Cadi 

and Joly (2004) found both weight loss and high mortality in the native turtle Emys 

orbicularis (L.) in mixed groups and argues for applying a precautionary principle. The 

introduced species also outcompetes the native turtle for preferred basking places (Cadi 

and Joly, 2003). The red-eared slider is one of the species mentioned in the Recommendations 

of the Bern Convention, as described above. 

Since no alien reptile species has established populations in Switzerland, no general 

pattern can be discussed here, except to note that the situation in neighbouring countries 

is rather similar. 

Reptiles depend to a large extent on climate, especially temperature, because they can 

regulate their body temperature only to a certain degree. Thus, tropical and subtropical 

species, which are most frequently kept in terrariums, are not of concern, apart from 

escapes of the occasional crocodilian or dangerous snake. However, this is more a 

matter of interest for the media than a true threat. A real concern for native biodiversity 

are species from North America and east Asia (China), mainly turtles, which could 

become established in the Swiss climate. Two measures should be implemented to 

restrict this threat: 

1. Raising awareness in the human population of the potential problem, and especially 

in herpetological clubs and organizations. 

2. Implementing laws to minimize releases and escapes of species which could potentially 

cause problems, e.g. article 25 of the Eidgenössisches Tierschutzgesetz (Swiss 

Animal Protection Act) stipulates the penalties for releases of this kind. 

Tab. 2.4 > Established alien reptiles in Switzerland. 


Natrix tessellata Colubridae Ticino – 1920s Released Competition with Natrix maura Relocation within Switzerland 

(Laurenti) Switzerland 

Emys orbicularis (L.) Emydidae ? 1800s? Released Genetic introgression with native populations? Re-introduction 

Trachemys scripta Emydidae North America Fairly recent Released Competition with native turtles in Europe Perhaps not established, but 

(Seidel) Escaped? Predator 

Destroying and disturbing floating bird nests 

long-lived


2.4 Amphibians – Amphibia 

Currently 20 amphibian species are found in Switzerland. One species (Rana ridibunda 

Pallas), i.e. 5 % of the total Swiss species number, is introduced and established and 

will be discussed below and in a Fact Sheet. A second species has been relocated 

within Switzerland (Triturus carnifex (Laurenti)) and a third species is found occasionally 

but has not yet been able to establish a population, i.e. the North American bullfrog 

Rana catesbeiana Shaw (Table 2.5). 

The marsh frog (Rana ridibunda) (see Fact Sheet) is the only introduced alien amphibian 

species at the national level. It was introduced between 1920 and 1950, probably 

from Hungary, as was the case with specimens released in the UK (Zeisset and 

Beebee, 2003). The most probable explanation for the introductions is that they were 

imports for human consumption. The marsh frog has now established with a wide 

distribution in Switzerland, mainly in the west and the Valais and in the north-eastern 

region. The species should not be supported, as native amphibian species are, by local 

conservation groups, and releases on conservation grounds or as a food resource need 

to be stopped. The role of the genetic peculiarities in the green frog complex are not 

fully understood, but in most places where the marsh frog is increasing the other two 

related species are decreasing. Thus, a displacement is evident. 

Another species introduced into a new range is the Italian crested newt (Triturus 

carnifex) (see Fact Sheet), which is native to the south of Switzerland (Ticino) but was 

introduced to the canton of Genève. Genetic studies showed that the Genève population 

is closest genetically to a population in Tuscany, Italy (Arntzen, 2001). Most probably 

the species was imported for zoological experiments and released into a pond at the 

University of Genève. It completely replaced the closely related great crested newt 

(Triturus cristatus (Laurenti)) in that area. However, it is a complex situation and there 

is hybridization between the two species. The distribution and spread of the Italian 

crested newt should be monitored to provide information for future decisions about this 

species and its threat. 

The American bullfrog (Rana catesbeiana) (see Fact Sheet) has not (yet) colonized 

Switzerland, but there are some recent unconfirmed records of the species. However, it 

is established in the neighbouring countries of Germany, France, and especially Italy in 

the Po valley with some rapidly expanding populations. Research has demonstrated its 

high potential to cause a decline in native amphibians and reptiles. Thus, bullfrogs 

should not be tolerated in the wild. Monitoring of suspect water bodies and raising 

awareness in the human population for this potential menace to native biodiversity is of 

high priority. 

In Switzerland only one frog is introduced and established, this is 5 % of the 20 amphibian 

species currently found in Switzerland. In Austria (Schuster and Rabitsch, 

2002) and Germany (Geiter et al., 2002) no established amphibians are listed, although 

it is possible that the American bullfrog has established unnoticed in the recent past –


there is an increasing number of records from Germany. The introduced species in 

Switzerland, the marsh frog, is native in Austria and Germany. 

Species of edible frogs may be illegally released as a food resource and game animal. 

In certain areas, notably western Switzerland, R. ridibunda is still imported in large 

numbers for human consumption and it is likely that some escape. This has been 

particularly true in the past with less rigid control of transport and containment. Thus, 

the current populations have most probably developed from these escapees. It seems 

likely also that some amphibians are released or escape from captivity as pets. Thus the 

pet trade should have a responsibility to educate the public about the potential threat of 

alien species to native biodiversity. Trade in certain species, such as the American 

bullfrog, should be prohibited. 

All three species discussed here are known to cause severe damage to native amphibians 

by preying on the smaller species, through competition as tadpoles, as vector of 

diseases, or through hybridization. No negative economic impact has been reported. 

The major recommendations to reduce the risks caused by alien amphibian species are: 

> A stricter regulation of the (pet) trade and implementation of laws and conventions. 

> Besides the legislative options, the public needs to be made aware of the potential 

threats to native biodiversity. Some of them might voluntarily act in a more responsible 

way. 

> Any established populations of American bullfrogs should be eradicated. 

Tab. 2.5 > Established alien amphibians in Switzerland. 


Rana ridibunda Ranidae East Europe, 1920s? Released (as food resource?) Competition with native amphibians Spreading 

Pallas probably Hungary Escaped from imports for Genetic changes in native green frog 

human consumption complex 

Triturus carnifex Salaman- South Europe, Few Released or escaped from Replaced the great crested newt Native to Switzerland 

(Laurenti) dridae including the Ticino decades containment for scientific 

ago studies 

Rana catesbeiana Ranidae Central and eastern Recent Released or escaped Feeding on native amphibians and Probably no breeding 

Shaw North America reptiles population in CH, as 

Competition with native amphibians 

Disease vector 

yet 

2.5 Fish – Pisces 

The situation with regard to introduced fish species in Switzerland is interesting because, 

with the exception of asp (Aspius aspius (L.)), all other species are individually 

mentioned in Appendixes 2 or 3 of the Fisheries Act of 1993 (Ordinance relevant to the 

federal fisheries law). In this Act, Appendix 2 describes situations (garden ponds,


aquaculture plants, etc.) in which certain alien fish taxa can be released without authorization, 

while Appendix 3 names fish taxa which are unwanted in Switzerland. In 

this section, species mentioned in these two Appendixes are referred to as Appendix 2 

and Appendix 3 species, respectively. A total of 15 species will be discussed below 

(Table 2.7), although in some cases natural breeding has not yet been reported from 

Switzerland. In such cases, populations are based on frequent releases. However, the 

species lists in Appendixes 2 and 3 suggest all 15 species should be dealt with here, 

since they are regulated in Switzerland. The common carp (Cyprinus carpio L.) is not 

included in the species discussed in this section, because it is assumed to be an archaeozoa, 

arriving with the Romans in Central Europe. It was also found in most of 

Europe before the glacial era. Organisms which occurred before glacial times in Central 

Europe often stimulate discussions about definitions of native and alien species. 

The bighead carp (Aristichthys nobilis Richardson) (see Fact Sheet) has not yet been 

reported to reproduce in Switzerland. However, it is assumed that the species could 

breed, and that is the reason for adding the species to Appendix 3. It is reported to 

breed in the Danube (Donau). 

The asp (Aspius aspius) is a very recent invader in Switzerland, first recorded in 1994 

in the Rhine (Rhein) at Basel (Zaugg et al., 2003). It is probably expanding its range 

following its introduction into the Rhine in Germany, downstream of Basel. Its natural 

range seems to be Central and eastern Europe from Germany eastwards, including the 

Danube system. The Rhine population was either introduced for fishing purposes 

(Ladiges and Vogt, 1979) or spread from the Danube after the completion of the Rhine–Danube 

Canal. This is the only alien fish species which was not introduced directly 

into Switzerland but into a neighbouring country, in this case Germany, and is naturally 

spreading up the river Rhine. The asp is a large fish (up to one metre long) and prefers 

large rivers. It is one of the few cyprinids that is a piscivore. The adults eat mainly fish, 

but also mammals and birds, while the more gregarious living young eat smaller animals 

such as invertebrates. It is assumed that the species will colonize more parts of 

Switzerland. Since the natural range is close to Switzerland, the species might be 

acceptable, as a natural expansion rather than an invasion. 

The goldfish (Carassius auratus (L.)) is a favourite species for aquariums and garden 

and park ponds. Today, it has acquired an almost pan-global distribution through its 

ornamental use. It either escapes or is released into the wild. Its native range is Central 

and eastern Asia. The Carassius species (two more are discussed below) are difficult to 

identify and some records might be misidentifications (Arnold, 1990). Goldfish feed on 

a wide range of food including plants and small animals. In some places they are 

regarded as a nuisance due to the production of stunted populations. They produce 

large numbers of individuals, which mature at a much reduced size, thereby diminishing 

the usefulness of the population for sport or commercial fishing (Lehtonen, 2002). 

There are indications that they compete with native fish species and increase turbidity 

through their bottom dwelling behaviour, as does the common carp, thereby altering 

the aquatic community. Introductions limited to closed systems are possible without 

authorization (Appendix 2 species).


The crucian carp (Carassius carassius (L.)) is probably native to Central and eastern 

Europe, but was widely distributed by humans throughout western Europe in the 

Middle Ages for fishing. It was in the recent past, if not still, being sold as a bait fish. 

The crucian carp is a hardy species that can survive adverse conditions, such as low 

oxygen levels and frost. It is also an Appendix 2 species, and therefore its use as a bait 

fish is illegal. The crucian carp is rarely found in Switzerland. 

The third Carassius species is the Prussian carp (Carassius gibelio (Bloch)). The 

taxonomy of the three Carassius species is complicated and this species is sometimes 

considered conspecific with C. auratus. The species are very similar in many ways, 

including appearance, biology, food and potential impact. The actual distribution and 

the history of introductions and spread are not well known, since the species were 

probably often misidentified (Arnold, 1990). The Prussian carp is listed in Appendix 2, 

thus its release outside contained captivity must be authorized. 

The grass carp (Ctenopharyngodon idella (Cuvier & Valenciensis) (see Fact Sheet) is 

of Chinese origin, but as it is one of the most important aquacultural fish, it has acquired 

a wide distribution on five continents. Although natural reproduction has not 

been reported in the wild in Switzerland, it is a species of concern because of its potential 

to cause massive impacts on ecosystems by removing higher aquatic plants and 

thereby causing shifts in the producer guilds to other plant species. This impact at the 

bottom of the food chain can cause major alterations to ecosystems. The grass carp 

showed some potential to control water weeds in Switzerland, but Müller (1995) 

concludes that it only controls the symptoms of eutrophication instead of ameliorating 

the causes of the deteriorating water quality. The grass carp is listed in Appendix 3 and 

therefore all releases are prohibited. 

The silver carp (Hypophthalmichthys molitrix (Valenciensis)) (see Fact Sheet) is a 

highly specialized phytoplankton feeder. In many cases it was released to reduce 

phytoplankton densities or stop algal blooms. Its origin is China, but today it is found 

in many countries around the world. Spawning requires very specific conditions, but 

has been recorded in the Danube. Its reproduction in Switzerland cannot be ruled out 

with certainty, so the species was included in Appendix 3. 

The stone moroko (Pseudorasbora parva (Temminck & Schlegel)) (see Fact Sheet) is 

a very small cyprinid. It is the only established fish species accidentally introduced to 

Europe and Switzerland, with shipments of grass carp from China. Whereas the deliberately 

introduced fish species are of value to the commercial or sports sectors, the 

stone moroko has no value to humans. Thus, the potential for conflicts over management 

and legislative measures for the species is reduced and it is an Appendix 3 species. 

The American catfish (Ameiurus melas and A. nebulosus (Le Sueur)) (see Fact Sheet) 

belong to the family Ictaluridae, which is restricted to the subtropical and temperate 

zones of North America, and were introduced into Europe to investigate their potential 

as a fish for human consumption. However, they are of little value. The two species are


very similar not only in appearance but also in their biology. They are listed in Appendix 

3, because of their potential negative impacts on native biodiversity. 

The brightly coloured pumpkinseed (Lepomis gibbosus (L.)) (see Fact Sheet) is an 

example of an ornamental fish introduced into Europe. It has an interesting breeding 

behaviour and is very showy. However, in some cases the species flourished and has 

reached high densities. In these circumstances, this predatory fish will almost certainly 

have an impact on the food web through selective feeding. It is an Appendix 3 species. 

One of the most popular sport fish in North America, the largemouth bass (Micropterus 

salmoides (Lacépède) (see Fact Sheet), was widely distributed in North America 

outside its natural range, and imported to Europe in the 1880s. The adult is a specialized 

fish predator and a decline in native fish species was observed in Italy after its 

introduction (Welcomme, 1988). It was also one factor, amongst others, in the extinction 

of the Atitlán grebe (Podilymbus gigas Griscom) which was endemic to Guatemala 

(BirdLife International, 2000). The bird’s population dropped drastically to 80 as 

a result of competition and predation by the introduced largemouth bass, but recovered 

to a high of 232 in 1975 when the numbers of the bass plummeted (LaBastille, 1984). 

Later the grebe became extinct through other factors. 

The only established alien Percidae is the pike-perch (Sander lucioperca (L.)), a 

species from Central and eastern Europe. It is one of the most popular sport fishing 

species and a highly priced commercial fish. Hence it has been widely released and has 

built up self-sustaining populations. It prefers large rivers and lakes, where it is a 

ferocious solitary pelagic predator. In the UK negative impacts on native fish populations 

have been confirmed; populations of Esox lucius L. and Perca fluviatilis L. 

declined after the introduction of pike-perch (Welcomme, 1988). In Switzerland, 

releases of the pike-perch without authorization are allowed in contained water bodies 

and where the pike-perch already occurs without negative effects on the fauna and flora 

(Appendix 2 species). However, the latter is difficult to prove or disprove, so that this 

predatory species can be released in many open waters. It was found in 137 localities 

during the survey for the fish atlas of Switzerland (Zaugg et al., 2003). More rigid 

legislation would be desirable for this species. 

The rainbow trout (Oncorhynchus mykiss Walbaum) is probably the most widely 

distributed freshwater fish species and may be regarded as a species of global distribution 

today. It is a highly prized game fish as well as being widely valued for commercial 

use. In Switzerland its natural reproduction is suspected but has been proved only 

in the ‘Alpine Rhinesystem’. The observed populations are probably based on extensive 

stocking of the species. Zaugg et al. (2003) found it in 39 % of the Swiss lakes and 

regarded it as a common species. A self-sustaining population is undesirable, because it 

would be difficult to control its spread or prevent competition for breeding grounds 

with the native brown trout (Salmo trutta ssp. fario L.). Where rainbow trout is extensively 

released, it will have a negative impact on native salmonids. Mahan (2002) 

showed that the introduction of the rainbow trout into a North American lake caused a 

decline of an endemic congeneric species (O. negratis) with local extinctions. Drake 

and Naiman (2000) explain the impact on the habitat. The exception of authorization


(Appendix 2 species) for stocking in alpine lakes should be re-addressed, because of 

the potential impact on amphibians. Amphibian populations in naturally fishless ponds 

and lakes will suffer from introductions of alien predatory fish species. 

A favourite species for fly-fishing, the brook trout (Salvelinus fontinalis (Mitchill)), is 

today a common species in alpine and subalpine lakes of Switzerland (Zaugg et al., 

2003). This species probably competes with the native brown trout. Impacts on lake 

communities have not been studied in Switzerland. In a North American study Bechara 

et al. (1992) investigated the impact of brook trout on native communities. Overall, 

their results suggest that size-selective predation by brook trout can cause profound 

changes in the structure of epibenthic communities at primary as well as secondary 

trophic levels. Releases of this species are restricted, since it is also an Appendix 2 


The lake trout (Salvelinus namaycush (Walbaum)) was chosen to stock many high 

altitude lakes based on its cold-tolerant, northern distribution in North America. It is a 

large predatory fish, which can probably cause negative impacts on native fish species. 

The lake trout is a favourite in recreational fishing. Stocking alpine lakes with this 

Appendix 2 species is permitted. This will have an effect on amphibians sharing the 

habitat. 

The frequent stocking of water bodies with alien fish species, and also native fish 

species from abroad, for sport and commercial fishing increases the possibility of 

introducing diseases (see for example the nematode Anguillicola crassus in the Nemathelminthes 

section in the chapter on ‘other selected invertbrate groups’), in addition 

to the issue of the potential establishment of the alien fish species themselves. Environmental 

risk studies are recommended before any fish introductions to investigate 

potential threats. Once the decision to introduce a species is taken, the material may be 

imported as eggs and some type of quarantine measures should be adopted for imported 

material prior to its release into natural waters. 

The 15 introduced species in Switzerland belong to five families (Fig. 1.1) (as explained 

above, not all of the species definitely have established populations, but they 

are included here, since they are listed in Appendixes 2 and 3). Two families are 

naturally restricted to North America, thus they are new to Switzerland. The Cyprinidae 

are the most species-rich family in the world with about 2,000 species, so it is not 

surprising that the highest number of native as well as introduced species belong to this 

family. It is also interesting to note that eleven families with only one species occur in 

Switzerland, although several had more members before some became extinct. Today 

50 % of the salmonids in Switzerland are introduced (three species). 

The high number of introduced salmonids reflects their popularity as game fish and for 

aquaculture. On the other hand, as Table 2.6 shows by comparing the total number of 

species per family and the number of species introduced to Switzerland, the number of 

species is a stochastic phenomenon – the smaller families produced a higher percentage 

of invaders.


Fig. 2.1 > Numbers of native and introduced fish species in different families in Switzerland. 

Salmonidae 

Thymallidae 

Coregonidae 

Esocidae 

Cottidae 

Percidae 

Gobiidae 

Centrarchidae 

Blenniidae 

Gasterosteidae 

Gadidae 

Siluridae 

Ictaluridae 

Cyprinidae 

Cobitidae 

Balitoridae 

Clupeidae 

Anguillidae 

0 5 10 15 20 25 30 35 

No. species 

Tab. 2.6 > Total number of members of five fish families worldwide and the number of species 

in these families introduced into Switzerland. 

Total no. species per 

family 

No. species introduced to 

Switzerland 

Native 

Introduced 

Percentage of introduced to total 

number [%] 

Cyprinidae 2000 8 0.4 

Ictaluridae 35 1 2.9 

Centrarchidae 30 2 6.7 

Percidae 159 1 0.6 

Salmonidae 66 3 4.5 

The lack of certainty about which species are actually established, and which of these 

are invasive, combined with the different definitions used in national reports, which 

leads to anomalies regarding which species are listed and how they are categorized, 

makes a comparison with other European countries such as Austria and Germany 

difficult. However, the situation appears to be very similar, with the exception of 

species from Central Europe which are native to Germany. As discussed above, many 

species are of North American and Asian origin and were widely introduced to Europe, 

so that they occur also in neighbouring countries. 

The 15 introduced species represent about 25 % of the current fish fauna. This value is 

fairly high compared with the figures for the other groups of vertebrates, in which 

introduced species form less than 10 % of the Swiss fauna. This reflects the economic 

importance of fish species, but also indicates the potential threat to native biodiversity.


The origin of the 15 species is obviously correlated with the climate, since all species 

are from temperate climates in the Northern Hemisphere, with six each from North 

America and Asia, and three from other parts of Europe. Mikschi (2002) lists two 

cichlid species for thermal waters in Austria, and these tropical species can only survive 

in these warm waters. Three other species from the Neotropics (Poeciliidae) 

became extinct after their release in the same waters. 

The exact pathways for fish introductions are often not known and in many cases 

introductions have been carried out with more than one motive. Taking the most likely 

pathways for each species, those released for commercial and sport fishing and aquaculture 

will amount to 11 of the 15 species. Two species are ornamental releases and 

escapes, and one was introduced as a control measure for unwanted vegetation. Interestingly, 

only one species arrived accidentally. However, its arrival is also connected 

with aquacultural practices, since it was a contaminant in grass carp shipments. In 

conclusion, the potential threats to native biodiversity are primarily due to fishing 

activities. Fish releases need to be considered carefully, their threats evaluated, and 

specimens quarantined to prevent spread of diseases. The number of introductions on a 

global scale has dramatically decreased since the 1960s, when they peaked, partially 

because growing awareness of possible negative consequences has led to legislation, 

but also because of a saturation effect as some species had been introduced to all 

suitable recipient areas (Welcomme, 1988). 

The demonstrated impacts of the 15 species are detailed in Table 2.7 and in the accounts 

for individual species, above. They encompass the entire range of effects measured, 

i.e. predatory and grazing pressure, competition with native species, changes in 

water quality, community and food-web changes, disease vectoring and hybridization. 

All potentially harmful species are regulated by Swiss law and are listed in Appendix 2 

or 3. This is a very good basis for management of alien fish species in Switzerland, 

although some of the Appendix 2 species which harm native biodiversity can be stocked 

in alpine lakes without authorization. This is especially worrisome in the case of 

predatory fish released into previously fishless lakes, where they can damage the 

amphibian populations. 

Therefore it is recommended that the species of Appendix 2 are re-addressed and 

stricter regulations are provided for those species. 

Another point of concern are species native to Switzerland released outside their native 

range, as noted in the sections of this chapter on reptiles and amphibians. The roach 

(Rutilus rutilus (L.)), for example, is native to the northern side of the Alps but was 

released in the Ticino, where it competes with the native fish fauna.


Tab. 2.7 > Alien fish species in Switzerland. 


Aristichthys nobilis Richardson Cyprinidae China ? Released for fishing Changes of community and habitat? Appendix 3 

species 

Aspius aspius (L.) Cyprinidae Central and 1994 Released for fishing in Harmless Not in the 

eastern Europe Germany Appendixes 

Migration through new 

canal systems 

Carassius auratus (L.) Cyprinidae Central and ? Released and escaped; Competition with native fish Appendix 2 

eastern Asia imported as ornamental species? species 

fish Community changes by increasing 

water turbidity? 

Carassius carassius (L.) Cyprinidae Europe ? Released for fishing Competition with native fish Appendix 2 

Bait fish species? species 

Community changes by increasing 


Carassius gibelio (Bloch) Cyprinidae Probably Asia ? Released for fishing Competition with native fish Appendix 2 

species? species 

Community changes by increasing 


Ctenopharyngodon idella (Cuvier Cyprinidae China ? Aquaculture Can change the ecosystem by Appendix 3 

& Valenciensis) Released to control removing aquatic plants species 

aquatic vegetation 

Hypophthalmichthys molitrix Cyprinidae China 1970 Released for control of Community and food-web changes Appendix 3 

(Valenciensis) phytoplankton by feeding on phytoplankton species 

Pseudorasbora parva (Temminck Cyprinidae East Asia 1990 Accidental introductions Community and food-web changes Appendix 3 

& Schlegel) with other cyprinid imports by selective feeding on zooplankton species 

Chances in water chemistry 

No commercial value 

Ameiurus melas and A. nebulosus Ictaluridae Central and ? Aquaculture Predator Appendix 3 

(Le Sueur) eastern North Aquarium releases Competition with native fish species species 

America Little commercial value 

Lepomis gibbosus (L.) Centrarchidae Eastern North ? Ornamental reasons Predator of small invertebrates and Appendix 3 

America Released for fishing vertebrates species 

Micropterus salmoides (Lacé- Centrarchidae Central and ? Released for fishing Decline of native fish species Appendix 3 

pède) eastern North species 

America 

Sander lucioperca (L.) Percidae Central and ? Released for fishing Ferocious predator Appendix 2 

eastern Europe species 

Oncorhynchus mykiss Walbaum Salmonidae North America 1887 Released for fishing Predator of native fish and am- Appendix 2 

Stock from Aquaculture phibians species 

Germany Competition with native salmonids 

Salvelinus fontinalis (Mitchill) Salmonidae Eastern parts of 1883 Released for fishing Competition with native salmonids Appendix 2 

North America Aquaculture species 

Stock from 

Germany 

Salvelinus namaycush (Walbaum) Salmonidae North America 1888 Released for fishing Predator of native fish Appendix 2 

Competition with native salmonids species


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3 > Crustaceans – Crustacea 65 

3 > Crustaceans – Crustacea 


It is not possible to draw up a comprehensive list of established alien crustaceans in 

Switzerland owing to gaps in knowledge for some groups and some regions. Another 

complicating factor is the rapid changes in species composition in the large rivers. 

Some new invaders are showing an explosive expansion in their ranges and densities. 

Despite these shortcomings, a preliminary list has been compiled using available 

information. As with all lists of alien and invasive alien species, it is crucial to update 

and add new information about distribution, impacts and management options as it 

becomes available. However, this list is believed to be a good basis for future expansion, 

since a comparison with neighbouring Austria shows similarities in species and 

species numbers. 

Table 3.1 summarizes available information on 17 established alien crustacean species 

in Switzerland. Six of them are considered to be harmful to the environment. More 

information on these species is presented in the Fact Sheets at the end of this chapter. 

There is little information available on Daphnia parvula Fordyce (Cladocera) and 

Atyaephyra desmaresti (Millet) (Atyidae) and their invasions might be of little significance 

for native biodiversity. 

The copepod Cyclops vicinus Uljanin is thought to have impacted native species by its 

predatory behaviour. 

The amphipod Corophium curvispinum (Sars) (Corophiidae) (see Fact Sheet) is a 

considerable threat to native ecosystems. This species is an ecosystem engineer and 

occurs at fairly high densities. In the Rhine between Basel and Bodensee it was the 

species with the third highest number of specimens per square metre, i.e. about 9,200 

individuals (Rey and Ortlepp, 2002). 

Six members of the family Gammaridae are established alien species in Swiss waters. 

Four of these are of Ponto–Caspian origin, while one invaded Central Europe from 

south-western Europe and one species came from North America. Of the three species 

Echinogammarus ischnus (Behning), E. trichiatus (Martynov) and E. berilloni Catta 

only the first-named is known to have a negative impact on the environment (see Table 

3.1), while insufficient is currently known about the other species to judge. The American 

species Gammarus tigrinus Sexton may change the food web after invasion. Two 

Dikerogammarus species have invaded Switzerland, D. haemobaphes (Eichwald) and


D. villosus (Soyinski). The latter species is the largerst of the invaders and has considerable 

impact on the ecosystem (see Fact Sheet). 

Introduced freshwater crayfish species, comprising four species in two families, 

Astacidae and Cambaridae, represent one of the greatest threats to Swiss biodiversity. 

Astacus leptodactylus Eschscholtz (see Fact Sheet) introduced from parts of southeastern 

Europe and south-western Asia is of least concern, although it can potentially 

compete with native crayfish. The other three species (Pacifastacus leniusculus (Dana), 

Orconectes limosus (Rafinesque) and Procambarus clarkii Girard) (see Fact Sheets) 

are of North American origin. They are not susceptible to the crayfish plague (see the 

chapter on Fungi), but they are vectors of the disease, carrying it into European crayfish 

(Astacus astacus (L.)) populations. The severity of the disease in these populations 

raises grave concerns about the survival of the native crayfish species. 

The three Isopoda species (see Table 3.1) may not pose a threat to Swiss freshwater 

ecosystems, despite the enormous densities of the tiny Ponto–Caspian invader Jaera 

istri Veuille. 

With respect to the taxonomic composition of the established species, two groups are 

dominant, i.e. the amphipods with seven species and the crayfish with four species. The 

amphipods are a successful group of about 6,000 species (Pöckl, 2002). They often 

dominate ecosystems in numbers of individuals as well as in biomass owing to their 

high fecundity under optimal conditions. Their omnivorous behaviour renders them 

adaptive to changing species compositions. The rapid invasions and build up of tremendous 

densities of alien amphipods are legendary. The interactions of native and 

rapidly invading alien species are very complex and difficult to understand. The fluctuations 

in densities are considerable and sometimes new invaders replace earlier 

invaders. Haas et al. (2002) give an overview of changes in abundance of alien species 

in the Rhine. The crayfish, as the second dominant group, belongs to the Decapoda, 

whose major centre of distribution is in North America and there are only a few species 

in Europe. The economic importance of crayfish is, of course, the major incentive for 

introducing alien crayfish into Europe. 

A comparison of alien crustaceans established in Switzerland and in neighbouring 

countries is not without flaws, because of gaps in knowledge. However, the 17 species 

listed here compare quite well with the 19 species recorded for Austria (Essl and 

Rabitsch, 2002). Geiter et al. (2002) list 26 species for Germany, but this includes 

species living in marine and brackish environments. 

The origin of the alien crustaceans established in Switzerland is equally divided between 

North America (including three crayfish species), the Ponto–Caspian region 

(five of the seven amphipods) and Mediterranean parts of Europe. The Ponto–Caspian 

region is essentially the area of the Black and Caspian Seas and their adjacent rivers. 

Many species endemic to the Ponto–Caspian region have become established in Europe, 

the Baltic Sea and, more recently, the Great Lakes in North America. This extraordinary 

spread has been facilitated by the construction of numerous canals allowing 

species to disperse by active migration and, to a greater extent, with ship traffic (in


ballast tanks and through hull-fouling). Many Ponto–Caspian crustaceans were also 

transplanted between water bodies as food for native fish to stimulate fish production 

within the former USSR. 

Although the exact time and place of the first introductions of many species are not 

documented, the data available suggest that many of them have invaded Switzerland 

fairly recently. Thus, further spread and increase in species densities in the short or 

long term are very likely. Moreover, other species are expected to arrive via river 

systems. 

With the exception of the crayfish species, almost all the crustacean invasions of 

Switzerland have been facilitated by the construction of canals and ship traffic. In most 

cases it is difficult to prove the exact pathways for the various species. Natural migration 

of some mobile species along rivers and canals is likely to be important over short 

distances. However, the rapid expansion of most species and some isolated records 

indicate spread by ship traffic, either in ballast tanks or on hulls. The crayfish species, 

however, were deliberately introduced as a food resource for human consumption. 

Additionally, escapees from aquaculture facilities have founded several populations. A 

third pathway is the importation of live crayfish for consumption. Crayfish are a delicacy 

and have to be added to boiling water alive. Thus, they are imported alive and 

some may have escaped. Moreover, some specimens escape from aquariums and 

garden ponds, or are released by their owners, who no longer want to keep them. 

The impacts of the species, especially the six high-risk species, are detailed in the Fact 

Sheets and in Table 3.1. The three North American crayfish species are of greatest 

concern with regard to the survival of the native crayfish populations, because they act 

as a vector of the devastating crayfish plague. The two amphipod species D. villosus 

and C. curvispinum alter the invaded habitats by predation, competition and causing 

changes to the substrate. Demonstrating impacts of alien species on native biodiversity 

and ecosystems is always difficult owing to the complex interactions. In conclusion, 

species thought to be harmless may turn out to have some, as yet undetected, negative 

impacts. This is especially true for freshwater ecosystems. Many of the alien species 

occur in enormous abundance. This must have some impact on the ecosystem, since 

each individual uses some resources and is a resource for others. Rey and Ortlepp 

(2002) found that the biomass in the Rhine near Basel was dominated by alien species 

– 97 % of the animal biomass and more than 90 % of the individuals were of alien 

origin. Thus, the original character of the Rhine has vanished; in this area it is not the 

typical Rhine anymore. Most of the alien species have invaded this stretch of the Rhine 

within the past five years. This suggests that their distribution will further expand and 

their dominance in other areas will increase. The dominance of alien species in European 

(and other continental) inland waters is dramatic. 

In most cases, eradication of established problematic species is not feasible. Control 

has limited success in open freshwater systems, such as rivers. Some species, in particular 

the crayfish, have economic value and intensive fishing could reduce their 

numbers. However, a reduction in the crayfish population might not be a sufficient 

goal, given the great threat they pose to native crayfish. One crayfish plague-infested


alien crayfish could be enough to wipe out a healthy population of their European 

relatives. Migrating specimens of alien crayfish were observed even in low-density 

situations, so a reduction might not prevent their spread. Thus, prevention of further 

introductions of species into and within Switzerland should have highest priority to 

safeguard native biodiversity and ecosystems. North American crayfish species are of 

greatest concern. With respect to releases of problematic freshwater species (e.g. for 

fishing and from aquarium dumping) an awareness-raising campaign would be crucial 

to sensitize the public to the potential problems caused by alien species. Accidental 

arrival of new species with ship traffic can only be minimized by effective treatment of 

ballast water and ships’ hulls. Crayfish species other than those mentioned above must 

be regulated too. An Australian species, Cherax destructor Clark for example, has been 

found in Switzerland (Stucki and Jean-Richard, 2000) and is being kept as a pet in 

aquariums and garden ponds owing to its beautiful appearance. The release of pets is 

illegal, but the unfortunate fact is that it is used as a way of getting rid of unwanted 

individuals, and they are also capable of escaping from ponds.


Tab. 3.1 > Established alien crustaceans in Switzerland. 

Scientific name Taxonomic Origin Year Pathway Impact Note 

group 

Daphnia parvula Fordyce Cladocera America 1972 Ship traffic Change in food web? First European record in the 

Bodensee (Lake Constance) 

Cyclops vicinus Uljanin Copepoda Europe 1954 Fish releases? Predator of native crusta- Found in the Bodensee. 

ceans 

Atyaephyra desmaresti Atyidae Mediterranean ? Expanding along No impact shown Likely to expand further throughout 

(Millet) canals, ship Europe 

traffic? 

Corophium curvispinum Corophiidae Ponto– 1980s Ballast water Change of ecosystem by Rapid colonization of the Rhine 

(Sars) Caspian Also migration transferring hard substrate to 

muddy areas. 

Reduces available habitat for 

hard substrate species 

Echinogammarus ischnus Gammaridae Ponto– 1990s Ship traffic Modifies substrate sediment. Invader of a large portion of Europe 

(Behning) Caspian Migration Alters energy flow between 

pelagic and benthic organisms. 

Additional prey for fish. 

Excludes competing species 

Echinogammarus Gammaridae Ponto– - Ship traffic Not known Likely to reach Switzerland in the 

trichiatus (Martynov) Caspian near future 

Echinogammarus berilloni Gammaridae South-western 20 th century Migration through Not known Probably still invading Europe 

Catta Europe canals 

Dikerogammarus Gammaridae Ponto– 1990s Ship traffic Not known Decreasing in Europe, because of 

haemobaphes (Eichwald) Caspian Migration the invasion of D. villosus 

Dikerogammarus villosus Gammaridae Ponto– Late 1990s Ship traffic Predator of alien and native Replacing earlier invaders 

(Sovinski) Caspian gammarids and other prey 

Gammarus tigrinus Gammaridae North America 1990s Ship traffic Changes in food web? Introduced from North America in 

Sexton Migration ballast water 

Astacus leptodactylus Astacidae South-eastern 1980s Release for Competition with native Important competitor for native 

Eschscholtz Europe fishing crayfish species crayfish species, but also vulnerable 

to the crayfish plague 

Pacifastacus leniusculus Astacidae North America ? Release for Competition with native Very destructive invader, displacing 

(Dana) fishing crayfish species native crayfish species 

Vector of the crayfish plague 

Orconectes limosus Cambaridae North America Before 1976 Release for Competition with native Very destructive invader, displacing 

(Rafinesque) fishing crayfish species. native crayfish species 


Procambarus clarkii Cambaridae Southern ? Release for Competition with native Very destructive invader, displacing 

Girard North America fishing crayfish species. native crayfish species 


Proasellus coxalis Asellidae South-western Second half Ship traffic Not known Rhine, but not common 

(Dollfuss) Europe of 20 th 

century 

Proasellus meridianus Asellidae South-western Second half Ship traffic Not known Rhine, near Basel, but not common 

(Racovitza) Europe of 20 th 

century 

Jaera istri Veuille Jaeridae Ponto– End of Ship traffic Not known, but very abun- One of the species with the highest 

Caspian 1990s dant abundance – likely to increase 

further


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4 > Insects – Insecta 71 

4 > Insects – Insecta 

Prepared by Marc Kenis 

4.1 Introduction 

Insects probably represent the most numerous exotic organisms in Switzerland. A list 

of insects that are considered to be of exotic origin has been drawn up, with the help of 

specialists (see Tables 4.1–4.6). It includes 311 species of exotic origin that have 

certainly or probably been introduced into Switzerland or neighbouring countries by 

human activities. It does not include species that are spreading naturally into Switzerland, 

unless they were first introduced into neighbouring countries. This list is by no 

means complete, but it will be maintained and new records will be added when data 

become available. In collaboration with taxonomists for the various insect groups, we 

also intend to publish this list in peer-reviewed journals, with more details on the 

occurrence, distribution and biology of the exotic species. The two published lists of 

alien organisms in Austria and Germany (Essl and Rabitsch, 2002; Geiter et al., 2002) 

have been of great help in the construction of the Swiss list. 

Many problems were encountered in drawing up the list, the main ones being detailed 

below. 

> There is an obvious lack of information sources in Switzerland. Up-to-date, published 

checklists are available for a few insect groups only (e.g. Diptera, Orthoptera, 

Odonata). The ‘Centre Suisse de Cartographie de la Faune’ (CSCF) is maintaining 

incomplete lists with the input of Swiss taxonomists, and several lists of other important 

insect groups are in the process of being completed (e.g. Coleoptera, Lepidoptera, 

Aphidoidea, etc.). The CSCF and individual taxonomists were very cooperative 

in helping us check and complete the list of exotic insects; nevertheless, it 

has been a rather difficult task. For some groups, there is presently little expertise in 

Switzerland, and no recent checklist is available (e.g. most primitive orders and 

Mallophaga, which are therefore not included in the list, and also parts of the Hymenoptera, 

Heteroptera, etc.). Additionally, it must be noted that in the few checklists 

published, the origin of the species is often not clearly indicated. For future 

checklists, we suggest including the ‘exotic character’ and the area of origin in the 

data set. 

> Many alien insects in Switzerland originate from the Mediterranean region. Some of 

these species, particularly Hemiptera, were evidently introduced with their host 

plants, which are often planted as ornamentals or crops in Switzerland. However, for 

other species, it is not clear whether they were introduced by human activities or 

arrived naturally (e.g. the Heteroptera Arocatus longiceps and Deraeocoris fla-


vilinea). Some species undoubtedly migrated unaided from southern Europe to 

Switzerland, possibly because of global warming. This is, for example, the case for 

the dragonflies Sympetrum meridionale (Selys) and Crocothemis erythraea (Brullé). 

Likewise, many Lepidoptera species (e.g. Helicoverpa armigera (Hübner) and 

Mythimna unipuncta (Haworth), which used to be observed only occasionally in 

summer in southern Switzerland, are now overwintering in the country more frequently. 

Eastern European insect species are also increasingly observed in Switzerland. 

For most of them, it is not clear whether their introduction into Switzerland 

was natural or by human-mediated transport, and whether they are firmly established 

or not. In general, species whose establishment in Switzerland seems to be the result 

of a natural process were not included in our list. However, this phenomenon would 

merit further studies. 

> High numbers of tropical or subtropical insects are found in Switzerland in houses, 

greenhouses and other confined environments. Many of them are important pests of 

greenhouse crops (e.g. several thrips and whiteflies) or stored products (e.g. various 

beetle and moth species). However, it is not always easy to determine whether these 

insects are firmly established, or regularly introduced from abroad with new plant 

material. Furthermore, some species that were thought to be confined to greenhouses 

are now found outdoors in natural environments. Examples include, among others, 

the scale insects Icerya purchasi, Coccus hesperidum and Dynaspidiotus britannicus 

(Kozar et al., 1994). 

> Today, many insects, particularly those feeding on stored products and crops and 

occurring as ectoparasites of vertebrates are considered to be of cosmopolitan distribution 

and, therefore, it is often difficult to assess their exotic status and some will 

finally be concluded to be cryptogenic species. Only insects that are suspected to be 

exotic, for any reason (e.g. because they feed only on an exotic plant, or because the 

genus is considered exotic) are included in the list. 

Invasive alien insects are serious threats to agriculture, economies, the environment 

and human and animal health worldwide. In some regions, such as North America, 

South Africa and many oceanic islands, exotic insect pests are considered to be as 

important as native pests, if not more so. Traditionally, problems have been less severe 

in Central Europe. Only a few exotic insects are known to cause serious damage in 

Switzerland, usually as stored product pests or on agricultural crops. However, in 

recent years several pests of economic importance have invaded Europe, stimulating 

more interest in the issue of exotic insects. For example, the western corn rootworm, 

Diabrotica virgifera ssp. virgifera is seriously threatening European maize production, 

and the horse chestnut leaf miner, Cameraria ohridella, is causing much public concern 

because of its spectacular damage to urban trees in Central Europe. 

Worldwide, environmental impacts have been studied less for alien insects than for 

other groups of invasive organisms such as plants or mammals. However, many insects 

are known to cause serious environmental damage in invaded habitats. Here again, 

most of these cases are from outside Europe. For example, the hemlock woolly adelgid, 

Adelges tsugae Annand, is threatening unique forest ecosystems in North America 

(Jenkins et al., 1999); the scale insect Orthezia insignis Browne was in the process of 

pushing the endemic gumwood tree Commidendrum robustum DC. in Saint Helena to


the brink extinction when a successful biological control programme was implemented 

(Fowler, 2004). In Europe, there have been few similar examples. Recently, however, 

the Argentine ant Linepithema humile has been causing changes in invertebrate and 

plant communities in the Mediterranean region by predation and displacement of native 

species (Gómez and Oliveras, 2003). The horse chestnut leaf miner is an urban pest in 

Central Europe but, in the Balkans, it is threatening the few remaining indigenous 

horse chestnut populations. In general, most alien insects have not been the targets of 

serious environmental impact studies. Their interaction with the native fauna and flora 

has been rarely investigated, particularly if their habitat is of little economic concern. 

Environmental impacts may be direct (on a plant for a herbivore, or on a prey for a 

predator), but the invader may also have an indirect impact on co-occurring organisms, 

e.g. through sharing the same food webs. Among the over 300 recorded exotic insects 

in Switzerland, surely more than one has an important environmental impact within the 

newly invaded ecosystem? Investigations on the impact of invasive species should not 

be restricted to species of economic importance, but should also focus on abundant 

species in poorly studied ecosystems, in which important environmental impacts may 

have been overlooked. 

The gaps in knowledge of the Swiss insect fauna, as explained at the beginning of this 

chapter, precludes any conclusive evaluation of its status, i.e. what percentage of the 

Swiss insect fauna is alien, the origins of the alien species, and the pathways by which 

they reached Switzerland. However, the fact that many species were apparently introduced 

with their host plants and food indicates that trade in commodities is a major 

pathway of insect introduction into Switzerland. Furthermore, it is certain that the 

majority of the alien insect fauna was accidentally introduced. Prevention of entry of 

pest species is addressed by quarantine regulations and interception; however, species 

of environmental concern are mostly not covered by these measures. Control of alien 

insect populations is also focussed on species of economic importance. 

4.2 Coleoptera 

There is no recent checklist of Coleoptera of Switzerland. However, Lucht (1987), in 

his catalogue of Coleoptera of Central Europe, includes distribution data for northern 

Switzerland. Furthermore, Claude Besuchet, Muséum d’Histoire Naturelle, Genève, is 

currently compiling a checklist for Switzerland, and he kindly helped us complete our 

list with his unpublished data. 

Over 120 beetle species are known, or suspected, to be of exotic origin in Switzerland, 

which accounts for about 40 % of the list of alien insects. Many of these exotic species 

are domestic pests, often feeding on stored products, construction material, etc. The 

main pests of stored products are found in the families Anobiidae, Bostrichidae, Bruchidae, 

Cucujidae, Curculionidae, Dermestidae, Mycetophagidae, Nitidulidae, Ptinidae, 

Silvanidae and Tenebrionidae. Most of them have been transported with their food and 

are now found worldwide. Their artificial cosmopolitan distribution renders the identification 

of their origin difficult. Some species, in particular many Dermestidae, may 

Advisor: 

Claude Besuchet, Muséum 

d’Histoire Naturelle, Genève


actually be native to Central Europe. Thus the inclusion of some species in the list is 

questionable. 

Some of the stored product pests are of tropical origin and are strictly domestic in 

Switzerland, whereas others can also survive and reproduce under outdoor conditions. 

Many more species than those listed in this study are found associated with stored 

products in Switzerland. However, it is not always clear whether these species are 

established, or regularly introduced with imported goods. Our list includes only the 

species thought to be established, although, in several cases, the decision on whether to 

include them or not was rather subjective. For example, we did not include the coffee 

bean beetle, Araecerus fasciculatus De Geer, a species often found in imported coffee 

and cocoa beans in Swiss food factories, but not clearly established in the country. 

Hoppe (1981) surveyed stored commodities in Switzerland and found the most destructive 

beetles to be the curculionids Sitophilus granarius and S. orizae, the silvanid 

Oryzaephilus surinamensis and the tenebrionids Tribolium castaneum and T. confusum, 

all considered to be of exotic origin. 

Apart from stored product pests, few exotic beetles are recorded as agricultural pests in 

Switzerland. However, two important chrysomelid beetles are worth mentioning. The 

infamous Colorado potato beetle, Leptinotarsa decemlineata invaded Europe from 

North America in the 1920s and reached Switzerland in 1937. It is a major pest of 

potato in Europe and North America (see Fact Sheet). More recently, the western corn 

rootworm, Diabrotica virgifera ssp. virgifera, a Nearctic species, took the same road 

and arrived in Belgrade in 1992. Twelve years on, it has spread to more than 12 European 

countries, including Switzerland (see Fact Sheet). D. virgifera virgifera is considered 

the major pest of maize in North America and substantial economic damage has 

already been observed in Central and eastern Europe. 

Some exotic beetles are damaging to forest and ornamental trees. Xylophagous insects 

are notorious for being easily introduced into new regions through the importation of 

timber or solid wood packing material. At least six Scolytidae in Switzerland are of 

alien origin. In particular, the Asian Xylosandrus germanus and the North American 

Gnathotrichus materiarius damage freshly cut logs and reduce timber quality. They 

both arrived in Switzerland in the 1980s (see Fact Sheet for X. germanus; Hirschheydt 

(1992) for G. materiarius). Other wood boring scolytids arrived in Switzerland very 

recently: Tripodendron laeve from East Asia or Scandinavia, Xyleborinus alni from 

East Asia, and Xyleborus punctulatus from Siberia (C. Besuchet, pers. comm.). Similarly, 

the cerambycids Neoclytus acuminatus and Xylotrechus stebbingi, xylophagous 

beetles from North America and the Himalayas, respectively, have recently been found 

in the Ticino (C. Besuchet, pers. comm.). Although these species have not yet caused 

economic or environmental damage in Switzerland, their introductions show that 

international movement of timber and timber products is an important introduction 

pathway for bark and wood boring beetles that may eventually lead to the establishment 

of serious forest pests. Among these potential introductions are the two Asian 

cerambycids Anoplophora glabripennis (Motschulsky) and A. chinensis (Forster). Both 

species are important pests in Asia, attacking and killing a whole range of tree species


(see Fact Sheets for both species). They were both introduced into North America in 

the 1990s, where they are now the targets of large-scale eradication programmes. 

These species have been often intercepted at ports of entry into Europe and, in the last 

four years, field populations have been found at various sites in Europe (in Austria, 

Germany and France for A. glabripennis; in Italy and France for A. chinensis). Eradication 

programmes have been established but the population of A. chinensis in Italy, at 

least, is considered to be established. The potential damage these two species could 

cause in Europe is unclear, but it could be spectacular. A. glabripennis is usually 

introduced as eggs, larvae or pupae in solid wood packing material, i.e. crating, pallets 

or packing blocks from China. A. chinensis has been transported to North America, 

France and Italy in bonsai trees from Asia. 

Not all introduced beetles in Switzerland are of economic importance. Many exotic 

species are found in decaying plant material, compost, litter, etc., in particular several 

fungus beetles (Latridiidae) and rove beetles (Staphylinidae), but also species in the 

families Hydrophilidae, Languridae, Merophysiidae, Orthoperidae, Ptiliidae, etc. 

Considering how little attention has been paid to these insects and their ecosystems, it 

is likely that many more exotic species remain unrecorded in Switzerland, and in 

Europe in general. Some of the recorded species are particularly abundant in their 

habitat, suggesting that direct or indirect interactions with the native fauna occur. 

Finally, another invasive beetle worth mentioning in the multicoloured Asian ladybeetle, 

Harmonia axyridis. This coccinellid is a biological control agent widely used in 

greenhouses against aphids. It recently became established outdoors in several European 

countries. The first specimen was found in Basel in 2004 (Klausnitzer, 2004). It is 

also established since the late 1980s in North America, where it has become a human 

nuisance because of its habit of invading houses and buildings in large numbers. Furthermore, 

it seems to decrease the diversity of native Coccinellidae, and it has also 

become a pest of fruit production, particularly in vineyards (see Fact Sheet). 

4.3 Lepidoptera 

The Lepidoptera of Central Europe has been quite well studied, and the distribution of 

both native and exotic species is fairly well known compared with most other insect 

orders. In this group, the main difficulty in establishing a list of exotic species came 

from the high numbers of Mediterranean species that are occasionally observed in 

Switzerland. The exotic or invasive status of most of these species is unclear. For 

example, Rezbanyai-Reser (2000) lists Mediterranean Geometridae and Noctuidae 

which occasionally overwinter in the Ticino. Some species apparently became established 

only recently, such as the noctuids Mythimna unipuncta and Acantholeucania 

loreyi (Duponchel), perhaps as a result of climate change. Others, such as the well 

known noctuid pest Spodoptera exigua (Hübner), are occasional visitors that can 

overwinter in the warmest areas of the country. Many other southern or eastern European 

species, including migrant species, are occasionally recorded in Switzerland. In 

general, these Lepidoptera are not included in our list, because their introduction and 

Advisors: 

Ladislaus Reser, Natur-Museum 

Luzern; Rudolf Bryner, Twann


establishment in Switzerland are natural phenomena and not mediated by human 

activity. A few species whose invasive status is in doubt are included in the list, such as 

the geometrid Eupithecia sinuosaria, a European species for which the spread through 

Central Europe has been particularly well studied (Rezbanyai-Reser et al., 1998). 

Similarly, Caradrina ingrata is a noctuid of eastern Mediterranean origin and is increasingly 

observed in urban areas, where it could have become established in warmer 

microclimates (Rezbanyai-Reser et al., 1997; Whitebread, 1997). 

Many Lepidoptera of exotic origin are primary or secondary pests. Among the bestknown 

exotic species are several leaf miners in the family Gracillariidae, which all 

invaded Europe in the last 30 years. Leaf miners are easily introduced into new areas 

because the mines on fresh or dead leaves are often inconspicuous and readily carried 

over long distances. In addition, several species pupate in or near the leaf mine, and 

these stages are less vulnerable to adverse conditions. The horse chestnut leaf miner, 

Cameraria ohridella, is a moth of unknown origin that was first found in Macedonia in 

1984 and in Switzerland in 1998 (Kenis and Forster, 1998; see also Fact Sheet). In less 

than 20 years, it has invaded most of Europe. The rapid spread of the moth in Europe is 

explained by the transport of adults and dead leaves containing pupae in or on vehicles. 

It causes severe defoliation to horse chestnut (Aesculus hippocastanum L.) trees in 

urban areas in most European regions as well as to indigenous horse chestnut stands in 

the Balkans, where it represents a threat to the survival of the tree species in the wild. 

The North American species Phyllonorycter robiniella and Parectopa robiniella mine 

leaves of their original host, the North American black locust Robinia pseudoacacia L. 

(see Fact Sheet in the plants chapter). Phyllonorycter platani, a moth originating from 

the Balkans and Asia Minor, is commonly found on Platanus trees. Phyllonorycter 

leucographella, also of eastern Mediterranean origin, has spread all over Europe and 

feeds on Pyracantha and Crataegus. Another gracillariid, the eastern Asian Caloptilia 

azaleella, mines on Rhododendron in greenhouses. Ornamental Cupressaceae in Europe 

are attacked by another North American leaf miner, the yponomeutid Argyresthia 

thuiella. 

The arctiid moth Hyphantria cunea is another interesting case of an invasive Lepidoptera. 

Originating from North America, H. cunea arrived in the 1940s in Hungary, from 

where it spread to most of Europe. It was first found in the Ticino in 1991 (Jermini et 

al., 1995; see also Fact Sheet). This polyphagous defoliator is considered a serious pest 

of forest and ornamental trees and shrubs in some eastern European countries and 

eastern Asia, where it was also introduced. Cydia molesta is an Asian species present 

in orchards in Switzerland where it feeds on various fruit trees. The noctuid Helicoverpa 

armigera is a cosmopolitan, polyphagous pest, probably of African origin, 

which occurs in Switzerland mainly in greenhouses. It is now also regularly found 

overwintering in the Tessin, where it probably arrived by itself. Another greenhouse 

pest of African origin is the banana moth, Opogona sacchari, which feeds on various 

woody and perennial ornamentals. 

Several exotic moths are pests of stored products in Switzerland. Most of them have 

been introduced with commodities into most parts of the world. The pyralid Plodia 

interpunctella is a major pest of stored products in warehouses, grain elevators and


food factories, as well as in private households. It feeds on grains, nuts and various 

other dried products. In Switzerland, it is particularly prevalent in chocolate factories, 

together with other pyralids, Ephestia elutella and Cadra cautella (Hoppe, 1981). The 

pyralids E. kuehniella and Sitotroga cerealella are also cosmopolitan species, found 

mainly in stored grains. These pests of stored products are usually well controlled in 

Switzerland and other developed countries, but their management makes extensive 

resource demands on the industry. 

4.4 Hymenoptera 

Only two Symphyta in the Swiss fauna are known to be of exotic origin. The wood 

wasp Sirex cyaneus is a secondary forest pest. Larvae live in dead or dying trunks of 

Abies, mainly, but also Larix and Pseudotsuga (Schwenke, 1982). The insect originates 

from North America but invaded Europe a long time ago, without causing damage. It is 

interesting to note that a European congeneric species, S. noctilio F., in Europe nearly 

as harmless as S. cyaneus, has become a major introduced pest of pine plantations in 

Australia, New Zealand, South Africa and South America. The second exotic sawfly in 

Switzerland is the nematine tenthredinid Nematus tibialis, an American species established 

in Europe where it feeds on its original host, Robinia pseudoacacia. 

Most Hymenoptera belong to the Apocrita, and of these the vast majority are parasitic 

insects. These are among the least known insects. There is no checklist of parasitic 

Hymenoptera for Switzerland, and new, undescribed species are found every year in 

Central Europe. Many European species are known to occur on other continents as well 

but, for most of them, it is impossible to know whether their wide distribution is the 

result of an introduction of exotic species into Europe, or vice versa. Only the few 

species deliberately introduced into Europe as part of biological control programmes 

are definitely exotic. For example, at least three alien parasitoid species have been 

introduced into Switzerland and have become permanently established. The aphelinid 

Aphelinus mali was released against the woolly aphid Eriosoma lanigerum as early as 

1922 (Greathead, 1976). Another aphelinid wasp, Encarsia perniciosi, was introduced 

more recently against the San José scale Quadraspidiotus perniciosus, and the dryinid 

Neodryinus typhlocybae was released in the Ticino in 1998–99 to control the flatid 

planthopper Metcalfa pruinosa (Mani and Baroffio, 1997; Jermini et al., 2000). Other 

parasitoids were released in neighbouring countries and were subsequently recovered 

in Switzerland, such as Aphytis proclia, Encarsia berlesei and E. lounhuryi, all introduced 

in Italy to control scale insects (Greathead, 1976; Noyes, 2002). The encyrtid 

Ooencyrtus kuvanae, an Asian egg parasitoid of the gypsy moth, Lymantria dispar L., 

was released in many European countries. It is has not been recorded from Switzerland, 

but since it is present in all neighbouring countries, there is no doubt that it also occurs 

in Switzerland (Greathead, 1976; Noyes, 2002). 

Other parasitic Hymenoptera of exotic origin are used as augmentative biological 

control agents in Swiss greenhouses. The most commonly used species, such as the 

whitefly parasitoid Encarsia formosa, are mentioned in our list because they have 

Advisor: 

Bernhard Seifert, Staatliches 

Museum für Naturkunde, Görlitz, 

Germany (Formicidae)


become part of greenhouse ecosystems although, in most cases, they cannot survive 

winter conditions outdoors. 

Many exotic seed chalcids of the genus Megastigmus (Torymidae) have been accidentally 

introduced into Europe with seed trading, some of them having become pests in 

European seed orchards (Roques and Skrzypczynska, 2003). Only M. spermothrophus, 

the North American Douglas fir seed chalcid, is reported from Switzerland, but many 

other species are known from neighbouring countries and, thus, are probably present in 

Switzerland. 

Two sphecid wasps have recently invaded Switzerland. The American Isodontia 

mexicana has been found in the Ticino and the Lemanic region since the early 1990s 

(Vernier, 1995, 2000). It feeds on crickets and, given its abundance, its impact on 

native ecosystems would merit further attention. Sceliphron curvatum is an Asian 

species which arrived in Europe in the 1970s. The first specimens were found recently 

in Switzerland (Gonseth et al., 2001). Its nests are commonly found in houses and other 

buildings. 

Five exotic ant species are recorded for the Swiss fauna (Freitag et al., 2000; Neumeyer 

and Seifert, 2005). These are ‘tramp’ ants of tropical and subtropical origin but transported 

by human activities to most regions of the world. The most common is the 

Asian species Monomorium pharaonis, very abundant in buildings and often considered 

as an urban pest. Hypoponera schauinslandi is found in greenhouses and other 

heated buildings in Central Europe (Seifert, 2004). Linepithema humile is the famous 

Argentine ant, which has invaded a vast territory along the Mediterranean coast and 

has been occasionally recorded in Switzerland (e.g. Kutter, 1981). Neumeyer and 

Seifert (2005) state that it could soon become established in outdoor situations because 

of global warming. Tapinoma melanocephalum and Paratrechina longicornis have 

been observed in few occasions indoors in Switzerland and their establishment is not 

firmly established (Dorn et al., 1997; Freitag et al., 2000). Another ant, Lasius neglectus 

Van Loon, Boomsma & Andrasfalvy, an Asian species, is rapidly invading Europe, 

causing some damage in urban areas (Seifert, 2000). It is not yet recorded from Switzerland, 

but its occurrence in neighbouring countries (France, Italy and Germany) 

suggests that it may be already present. 

Finally, the chestnut gallwasp, Dryocosmus kuriphilus Yasumatsu (Hym.: Cynipidae), 

is worth mentioning as a potential threat for the European chestnut, Castanea sativa, in 

Switzerland and the rest of Europe. This Chinese species was found for the first time in 

Northern Italy in 2002 and is considered as the most serious insect pest of Castanea 

spp. worldwide (Bosio, 2004). Attacks of Dryocosmus kuriphilus reduce growth of 

young chestnuts and fruiting. Yield reductions of 50–70 % are observed and severe 

infestations may result in the dead of the tree.


4.5 Diptera 

Checklists of Swiss Diptera have been published recently (Merz et al., 1998, 2001). 

These do not contain information on the exotic or invasive status of the species but the 

authors (Drs. B. Merz, J.-P. Haenni and G. Baechli) were contacted and kindly reviewed 

the list to extract the species which are thought to be exotic. 

Less than 20 dipteran species in Switzerland are of alien origin. Some are agricultural 

or horticultural pests. The Nearctic agromyzids Liriomyza huidobrensis and L. trifolii 

are pests of vegetables, mainly in greenhouses but occasionally found outdoors. Another 

agromyzid fly, Napomyza gymnostoma, was recently found in Switzerland (Eder 

and Bauer, 2003). N. gymnostoma, previously known as a harmless insect from some 

European countries, but not Switzerland, mysteriously became a serious pest of onions 

and leeks one or two decades ago in several Central and western European countries. 

Its origin is not known, although it may be a virulent ecotype of a European species 

that unexpectedly adapted itself to agricultural systems and crops. Its sudden pest status 

and spread may also be due to changes in pest control methods in leek and onion crops, 

or to global warming. 

Two of the world’s most serious fruit flies (Tephritidae), the olive fly Bactrocera oleae 

and the Mediterranean fruit fly, Ceratitis capitata, both originating from the Mediterranean 

region, are also established in Switzerland, where they have reached their 

climatic limit and, thus, cause little damage. Two North American tephritids have 

recently invaded the country. Rhagoletis completa feeds on walnut and is considered a 

pest in its native region. It was discovered in the Ticino in 1991 (Merz, 1991) and, 

since then, has spread rapidly to many regions north of the Alps (see Fact Sheet). 

Populations are increasing and severe damage has been observed in Switzerland and 

Italy. Another American species, R. cingulata, was found at the same time, in cherries 

(Merz, 1991, as R. indifferens). Until now, populations have remained very low and it 

does not seem to spread as quickly as R. completa. 

The North American Drosophilidae Chymomyza amoena attacks various fruits of 

broadleaved trees, such as apple, walnut, plum, acorn, etc. It is present in high numbers 

in both urban and forest environments. Its spread and ecology in Switzerland have been 

studied in detail (e.g. Burla and Baechli, 1992; Band, 1995; Band et al., 1998, 1999). 

Another drosophilid, Drosophila curvispina, originating from east Asia, is present in 

the Ticino, Vaud and Valais (Bächli et al., 2002; Bächli, pers. comm.). 

Other alien Diptera occurring in Switzerland are saprophagous or coprophagous. These 

species are often of cosmopolitan distribution. The calliphorid Chrysomya albiceps and 

the muscid Hydrotaea aenescens are found on human cadavers and other decaying 

matters. The black soldier fly, Hermetia illucens (Stratiomyidae), was found in very 

high numbers in composted plants in the Ticino (Sauter, 1989). In North America, this 

very common species is often associated with poultry houses and other farming or 

animal-rearing activities. Only one milichiid, Desmometopa varipalpis, is mentioned in 

our list as clearly exotic. However, the Milichiidae are small, often cosmopolitan and 

Advisors: 

Bernhard Merz, Muséum 

d’Histoire Naturelle, Genève; 

Jean-Paul Haenni, Muséum 

d’Histoire Naturelle, Neuchâtel; 

Gerhard Baechli, Zoologisches 

Museum, Zürich; Wolfgang Billen, 

Amt für Landwirtschaft, Lörrach, 

Germany


poorly known insects, and it is possible that other milichiid members of the Swiss 

fauna are also of exotic origin (B. Merz, pers. comm.) 

Exotic mosquitos (Culicidae) represent a major threat to human health worldwide. The 

tiger mosquito, Aedes albopictus, was found in Switzerland for the first time in the 

Ticino in 2003 (see Fact Sheet). Besides causing human nuisance through its bites, A. 

albopticus is also a potential vector of various illnesses. In Asia, its region of origin, it 

is a natural vector of dengue fever and other arboviruses, as well as filaria for both 

human and domestic animals. In North America, it is a vector of the West Nile virus. 

4.6 Hemiptera 

This order probably encompasses the highest number of exotic pests worldwide. Small 

Hemiptera, particularly aphids, scales, whiteflies and psyllids, are very easily carried 

around the globe on plant material. Many are pests of worldwide distribution and it is 

sometimes difficult to assess their region of origin. Among the cosmopolitan species of 

doubtful origin and listed as exotic in Switzerland, for example, are the aphids Myzus 

persicae, Aphis gossypii and Cinara cupressi, the whitefly Bemisia tabaci, and the 

scales Dynaspidiotus britannicus, Quadraspidiotus pyri and Planococcus citri. Many 

other cosmopolitan species are not included in this list because they are supposed to be 

of European origin (e.g. the aphids Acyrthosiphon pisum, Brevicoryne brassicae and 

Rhopalosiphum padi), although their origin is unclear and the possibility that they 

entered Switzerland a long time ago cannot be ruled out. 

Another problem, particularly prevalent in Hemiptera, is the high number of tropical or 

subtropical pest species introduced into greenhouses with their host plants. The most 

abundant species have been included in the list because there is no doubt that they have 

become established in Switzerland in indoor conditions. For example, the aphid Aphis 

gossypii, the whiteflies Bemisia tabaci and Trialeurodes vaporarium and the scale 

Planococcus citri are recurrent problems in protected crops and plants in Switzerland. 

Many other tropical and subtropical species are occasionally reported from greenhouses 

and indoor plants, but it is difficult to say whether their presence results from a 

permanent establishment or from regular introductions. In addition to those species 

included in our list, Kozar et al. (1994) mentions several species of scale insects that 

have been recovered from greenhouses and indoor plants in Switzerland. Interestingly, 

three of these scale species previously known only from greenhouses (Diaspidiotus 

distinctus, Coccus hesperidum and Icerya purchasi) are now found established in the 

field (Kozar et al., 1994). Other ‘greenhouse’ Hemiptera of exotic origin and not 

mentioned in our list are bug species of the genera Orius and Xylocoris (Anthocoridae), 

commonly used as biological control agents against thrips, spider mites or aphids. 

Many hemipteran species in Switzerland have migrated from neighbouring countries, 

especially the Mediterranean region. In most cases these have probably been introduced 

with their host plant. For example, most Psyllidae and Triozidae, included in the 

list feed specifically on plants of Mediterranean origin which are used in Switzerland 

Advisors: 

Daniel Burckhardt, 

Naturhistorisches Museum Basel 

(Psyllina); Gerolf Lampel, Pensier, 

and Yves Gonseth, Centre Suisse 

de Cartographie de la Faune, 

Neuchâtel (Aphidina); Ralf 

Heckmann, Konstanz, Germany 

(Heteroptera)


as ornamentals. However, other southern European species may have entered Switzerland 

independently. In particular, four true bugs, the lygaeids Arocatus longiceps, 

Orsillus depressus and Oxycarenus lavaterae, and the mirid Deraeocoris flavilinea are 

clearly expanding their range from southern to Central Europe (e.g. Adlbauer and 

Rabitsch, 2000; Rabitsch, 2002). Whether the spread is purely natural or not remains 

unclear. 

Most of the known exotic Hemiptera included in the list are recognized as pests, feeding 

on crops, ornamentals and forest trees in Switzerland. It is likely that many other 

exotic Hemiptera remain undetected because they feed on non-commercial plants. 

Among aphids, one of the best-known cases of exotic pests in Europe is the grape 

phylloxera, Viteus vitifoliae which invaded Europe from North America in the 19 th 

century, causing serious damage to vineyards and endangering the European wine 

industry. The problem was solved by grafting European cultivars on less susceptible 

American rootstocks; however, the level of damage has increased again in recent years, 

including in Switzerland. Other aphid species, such as Myzus persicae, Macrosiphum 

euphorbiae and Aphis gossypii, attack a wide range of vegetable crops, both indoors 

and outdoors. They are also vectors of serious viral diseases. The Russian wheat aphid, 

Diuraphis noxia (Kurdjumov), a serious pest of cereals, has not yet been reported from 

Switzerland, but has already invaded France, Italy and Austria (CABI, 2001; Lethmayer 

and Rabitsch, 2002). Orchard trees in Switzerland, in particular apple trees, can 

be severely damaged by the North American woolly aphid Eriosoma lanigerum and the 

Asian Aphis spiraecola. In forestry, the most serious exotic aphid is certainly the 

woolly aphid Dreyfusia nordmannianae, a pest of firs (Abies) of Caucasian origin, but 

other species such as Gilletteella cooleyi on Pseudotsuga and Elatobium abietinum on 

Picea, both from North America, may cause some concern to foresters. 

Only two exotic whitefly species (Aleyrodidae) are known to occur in Switzerland, 

Bemisia tabaci and Trialeurodes vaporarium, but these are among the main pests of 

vegetables in greenhouses. Control is achieved using aphelinid parasitoids in the 

genera Encarsia and Eretmocerus. 

A number of exotic scale insects are also known as pests in Switzerland, particularly on 

orchard and ornamental trees. The San José scale, Quadraspidiotus perniciosus, is an 

Asian species that has invaded nearly all continents, including Europe, where it is still 

expanding its range. It is already distributed in most parts of Switzerland, where it 

causes serious damage to orchards, particularly apple, peach and plum (see Fact Sheet). 

Another congeneric species, Q. pyri, also attacks fruit trees, but its origin remains 

uncertain, and it may be indigenous. In recent years, serious damage by scale insects 

has been observed on urban trees. The diaspidid Pseudaulacaspis pentagona, an insect 

of Asian origin and known to be polyphagous attacking mainly mulberry and peach 

trees, has caused severe damage to ornamental trees such as Sophora, Aesculus and 

Catalpa in Swiss cities (Mani et al., 1997). Similarly, the coccid Pulvinaria regalis 

(see Fact Sheet) is a polyphagous exotic species of uncertain origin that has recently 

caused heavy damage to Tilia and Aesculus in Zürich (Hippe and Frey, 1999).


Only seven species of Auchenorrhyncha are listed as exotic in Switzerland. However, 

some of them are of economic importance. Metcalfa pruinosa, a flatid planthopper of 

American origin, has recently invaded the Ticino through Italy (see Fact Sheet). This 

polyphagous species is found on many trees and shrubs, but also on crops such as 

soyabean. It can be particularly harmful to fruits such as grape, pear, apple, citrus and 

peach. It is expected that M. pruinosa will expand its distribution to most of Switzerland. 

Another North American species, the vine leafhopper Scaphoideus titatus, recently 

entered Switzerland. It does not cause direct damage to vine, but it transmits a 

severe mycoplasma disease, the ‘flavescence dorée’ (Günthart, 1987). Two other North 

American species are present in Switzerland, the cicadellid leafhopper Graphocephala 

fennahi on Rhododendron, and the membracid treehopper Stictocephala bisonia, a 

polyphagous species found mainly in orchards, but neither of them causes serious 

damage. 

The only heteropteran bugs of non-European origin known to occur in Switzerland are 

the two North American lace bugs Corythucha ciliata and Corythucha arcuata. 

C. ciliata is a serious pest of Platanus in urban areas in Europe. Heavy infestations 

cause discolouration of leaves and premature leaf fall. It was first observed in Switzerland 

in 1983 and its distribution now covers most of western Switzerland (see Fact 

Sheet). Corythucha arcuata is a similar species, feeding on oak. It was first found in 

Italy in 2000 and in 2003 in Switzerland (Ticino) (see Fact Sheet). Similarly, another 

American bug, the coreid Leptoglossus occidentalis Heidemann, has recently been 

found in high numbers in northern Italy. It feeds on various conifer seeds and is considered 

a serious pest in seed orchards in North America (Villa et al., 2001). 

4.7 Orthoptera 

The Orthoptera of Switzerland and their distributions are listed in Thorens and Nadig 

(1997). Only two species established in the country are clearly exotic. The house 

cricket Acheta domesticus is a cosmopolitan species, probably of North African origin. 

In Central Europe, it lives mainly in buildings, although in summer it is also commonly 

found outdoors, particularly in the Valais. The house cricket is omnivorous, feeding 

mainly on refuse and, occasionally, on stored products. 

The greenhouse camel cricket, Tachycines asynomorus, probably originates from east 

Asia, but is now found worldwide. It was introduced into Europe in the 19 th century. In 

Switzerland, it lives mainly in greenhouses, where it feeds on fruits, seedlings and 

insects. It is also occasionally found outdoors, e.g. in botanical gardens. 

Some Mediterranean species such as the Egyptian grasshopper Anacridium aegyptium 

(L.) are occasionally caught in Switzerland. Specimens found in the Ticino may have 

migrated from the South, however, it seems that at least some catches in various regions 

may be related to the importation of food products. (Nadig and Thorens, 1991; 

Rezbanyai-Reser, 1993). 

Advisor: 

Hannes Bauer, Naturhistorisches 

Museum, Bern


4.8 Dictyoptera 

At least five exotic cockroach species are known to be established in Switzerland. 

Others may be introduced occasionally with imported goods. Unlike the native cockroaches, 

the exotic species are synanthropic, i.e. they are always found in association 

with humans. These cockroaches are of tropical and subtropical origin but they now 

occur worldwide. Some species, such as Blatta orientalis and Periplaneta americana, 

have been cosmopolitan for such a long time that their origin is uncertain. B. orientalis, 

P. americana, P. australasiae and B. germanica have been established in Switzerland 

for a long time, whereas Supella longipalpa is a recent introduction. 

All these species are considered as serious urban pests. They are gregarious, nocturnal, 

and difficult to eradicate in houses. They can eat almost anything, e.g. human food and 

animal feed, bookbindings, wallpaper, excrement, leather products, etc. They can carry 

organisms causing human diseases, have a repulsive odour, and can cause allergic 

reaction and anxiety in some individuals. In Switzerland, the most problematic species 

are B. germanica, S. longipalpa and B. orientalis, whereas Periplaneta spp. are of 

minor importance (Landau et al., 1999). 

4.9 Isoptera 

There is no record of establishment of exotic termites in Switzerland. However, in 

recent years, subterranean termites of the genus Reticulitermes have invaded new areas 

(see Fact Sheet). The North American R. flavipes (Kollar) is introduced in some German 

and Austrian cities. The southern European R. grassei Clément occurs now in 

southern England and R. santonensis de Feytaud, a species of uncertain origin (and 

perhaps synonymous with R. flavipes) has spread from south-western to northern 

France. These termites undoubtedly have the potential to invade the warmest areas in 

Switzerland. They live in colonies in the soil, mainly in urban areas. They are particularly 

harmful to wooden elements in building but can also attack living trees. The 

spread of subterranean termites in France is causing major concern. New regulations 

have been set up to limit the spread. 

4.10 Thysanoptera 

Many exotic thrips species are found, regularly or occasionally, in Switzerland in 

greenhouses. However, it is not always clear whether they are firmly established in the 

country. At least four species are considered permanently established, mainly in greenhouses. 

Three of them, Frankliniella intonsa, F. occidentalis and Heliothrips haemorrhoidalis 

are polyphagous, cosmopolitan pests on ornamentals, vegetables, and fruits. 

F. occidentalis, the western flower thrips, is among the most destructive greenhouse 

pests in Switzerland (Ebener et al., 1989; Schmidt and Frey, 1995). It is also a vector of 

various viruses. The pest status of F. occidentalis is relatively recent. It occurs naturally 

in North America on wild flowers and emerged as a greenhouse pest in the Neth-


erlands in 1983. Since then, it has spread all around the world (CABI, 2001). In Switzerland, 

F. intonsa is particularly associated with strawberry crops (Linder et al., 

1998). 

The gladiolus thrips, Thrips simplex, originates from South Africa and was introduced 

in many regions with gladiolus corms. It reproduces only on gladiolus corms and 

leaves but adults are found on many other plants (CABI, 2001). In Switzerland, it does 

not survive outdoors. 

4.11 Psocoptera 

Psocoptera, or psocids, are rather poorly known insects. Most species live in woodlands, 

but some are domestic, i.e. they inhabit houses, warehouses, etc., feeding on 

organic matter. The domestic species can become a nuisance, although they rarely 

cause economic damage. Partial European and Swiss lists of Psocoptera exist, but the 

origin of the species is often unclear. Lienhard (1994) lists 29 species that are totally, 

essentially or occasionally domestic in Switzerland. Most of them are not, or very 

rarely, found in the field, suggesting that they are not indigenous. We have included in 

our list the species that Lienhard (1994) mentions as exclusively or essentially domestic 

in Switzerland, keeping in mind that some of them might be indigenous but poorly 

known in their natural habitat. 

Three species of the genus Dorypteryx are most likely of exotic origin. Their spread in 

Europe is illustrated in Lienhard (1994). D. domestica, described from Zimbabwe in 

1958, was first found in Switzerland in 1973. From there, it has spread rapidly to most 

European countries where it has become one of the most frequent domestic species. D. 

longipennis, a species of unknown origin, was first found in Luxembourg in 1988. It 

reached Switzerland in 1992 and is now spreading very rapidly. D. pallida is an older 

introduction. It was first described from North America, and found in Germany in 

1890. Its spread seems to be slower than that of the other two species. Other species 

that are most probably exotic include Liposcelis mendax, Ectopsocus pumilis and E. 

richardsi, which have been found associated with an importation of dry mushrooms 

from Asia. Whether these rare species are established in Switzerland is unclear. Other 

species are found outdoors in the Mediterranean regions but only indoors in Switzerland, 

e.g. Trogium pulsatorium and Ectopsocus vachoni. 

4.12 Ectoparasites 

Ectoparasitic insects of vertebrates include mainly Siphonaptera (fleas – on birds and 

mammals), Anoplura (sucking lice – on mammals) and Mallophaga (biting lice – on 

birds and mammals). Undoubtedly, several of the ectoparasites present in Switzerland 

are allochtonous, having arrived in the region with their hosts. However, these insects 

are rather poorly studied, particularly in Switzerland, and their origin is often unclear. 

In their work on the Siphonaptera of France and the western Mediterranean region, 

Advisor: 

Yves Gonseth, Centre Suisse de 

Cartographie de la Faune, 

Neuchâtel


Beaucournu and Launay (1990) provided data for Switzerland. At least two fleas 

appear to be definitely exotic in the country. The cat flea, Ctenocephalides felis felis, 

has a cosmopolitan distribution but is probably not of European origin (Beaucournu 

and Launay, 1990). The rabbit flea, Spilopsylus cuniculi, is a vector of myxomatosis 

and probably originates, like its host, from the Iberian Peninsula, while the disease was 

introduced into Europe from South America. Some other fleas present in Switzerland 

are of doubtful origin and are not included in the list. For example, the human flea 

Pulex irritans L., which feeds on many carnivores, is now cosmopolitan but belongs to 

a Nearctic genus. However, its arrival in Europe was probably in the distant past. 

Büttiker and Mahnert (1978) listed 25 Anoplura for Switzerland. Only one, Haemodipsus 

ventricosus, is very likely to be of exotic origin because it seems to be restricted to 

rabbits. Sucking lice of doubtful origin include the cosmopolitan rat louse, Polyplax 

spinulosa (Burmeister), and the dog sucking louse, Linognathus setosus (v. Olfers). 

There is no recent list of Mallophaga for Switzerland. Mey (1988) provides a list of 

mammalian Mallophaga in Europe, but data for Switzerland are scarce. Three South 

American species, Gyropus ovalis Burmeister, Gliricola porcelli (Schrank) and Trimenopon 

hispidum (Burmeister), are found on guinea pigs in neighbouring countries 

and, thus, are probably present in Switzerland. Similarly, it is possible that the Nearctic 

Trichodectes octomaculatus Paine and Pitrufquenia coypus Marelli, parasites on 

raccoons and coypus, respectively, in Central Europe, are present in Switzerland with 

their host. 

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thrips Frankliniella occidentalis in greenhouses. Mededelingen Faculteit 

Landbouwkundige en Toegepaste Biologische Wetenschappen, 

Universiteit Gent 60, 847–850. 

Schwenke, W. (ed) (1972) Die Forstschädlinge Europas, I. Band. Würmer, 

Schnecken, Spinnentier, Tausendfüssler und Hemimetabole Insecten. 

Paul Parey, Hamburg and Berlin. 

Schwenke, W. (ed) (1982) Die Forstschädlinge Europas, 4. Band. 

Hautflüger und Zweiflüger. Paul Parey, Hamburg and Berlin. 

Seifert, B. (2000) Rapid range expansion in Lasius neglectus 

(Hymenoptera: Formicidae) – an Asian invader swamps Europe. 

Mitteilungen aus dem 

Museum für Naturkunde in Berlin. Deutsche Entomologische Zeitschrift 

47, 173–179. 

Seifert, B. (2004) Hypoponera punctatissima (Roger) and H. schauinslandi 

(Emery) – tow morphologically and biologically distinct species 

(Hymenoptera: Formicidae). Abhandlungen und Berichte des 

Naturkundemuseums Görlitz 75, 61–81. 

Skuhrava, M. and V. Skuhravy (1997) Gall midges (Diptera: 

Cecidomyiidae) of Switzerland. Mitteilungen der Schweizerischen 


Stary, P. (1995) Natural enemy spectrum of Aphis spiraephaga (Hom., 

Aphididae), an exotic immigrant aphid in Central Europe. Entomophaga 

40, 29–34. 

Thorens, P. and A. Nadig (1997) Atlas de distribution des orthopteres de 

Suisse: sauterelles, grillons, criquets (Orthoptera), mante religieuse 

(Mantodea). Centre Suisse de Cartographie de la Faune, Neuchâtel. 

Vernier, R. (1995) Isodontia mexicana (Sauss.), un Sphecini américain 

naturalisé en Suisse (Hymenoptera, Sphecidae). Mitteilungen der 


Vernier, R. (2000) Isodontia mexicana (Sauss.) (Hymenoptera, Sphecidae) 

est apparu dans le Bassin lémanique. Bulletin Roman d’Entomologie 18, 

143–145. 

Villa, M., Tescari, G. and S.J. Taylor (2001) Nuovi dati sulla presenza in 

Italia di Leptoglossus occidentalis (Heteroptera Coreidae). Bolletino della 

Societa Entomologica Italiana 133, 103–112. 

Watson, G.W., Voegtlin, D.J. Murphy, S.T. and R.G. Foottit (1999) 

Biogeography of the Cinara cupressi complex (Hemiptera: Aphididae) on 

Cupressaceae, with description of a pest species introduced into Africa. 

Bulletin of Entomological Research 89, 271–283. 

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als unerwünschter Gast im Hause (Lepidoptera: Noctuidae). Mitteilungen 

der Entomologischen Gesellschaft Basel 47, 9–11.


Tab. 4.1 > Established alien Insects in Switzerland: Coleoptera. 

Species Habitat – life traits Origin Reference for Switzerland 

COLEOPTERA 

Anobiidae 

Lasioderma serricorne (F.) Stored products, especially tobacco Tropics and subtropics C.Besuchet, pers. comm. 

Stegobium paniceum (L.) Stored products, very polyphagous Cosmopolitan Lucht, 1987 

Oligomerus ptilinoides (Wollaston) Feeds on wood products Mediterranean region, possibly C. Besuchet, pers. comm. 

native 

Anthicidae 

Stricticomus tobias Marseul Feeds on rotten plant tissue Asia Minor, Central Asia, India C. Besuchet, pers. comm. 

Apionidae 

Alocentron curvirostre (Gyllenhal) In stems of Alcea rosea L. Asia, Middle East C. Besuchet, pers. comm. 

Aspidapion validum (Germar) In fruits of Alcea rosea Asia, Middle East C. Besuchet, pers. comm. 

Rhopalapion longirostre (Olivier) In seeds of Alcea rosea Asia, Middle East C. Besuchet, pers. comm. 

Bostrichidae 

Rhyzoperta dominica (F.) Stored products, mainly cereals Tropics and subtropics C. Besuchet, pers. comm. 

Bruchidae 

Acanthoscelides obtectus (Say) In leguminous seeds, mainly beans South and Central America Lucht, 1987 

Acanthoscelides pallidipennis (Motschulsky) In seeds of Amorpha fruticosa North America C. Besuchet, pers. comm. 

Bruchus pisorum (L.) In peas North America or Near East Lucht, 1987 

Callosobruchus chinensis (L.) In leguminous seeds East Asia C. Besuchet, pers. comm. 

Buprestidae 

Agrilus guerini Lacordaire Xylophagous, on Salix Eastern Europe, Russia? Barbalat and Wermelinger, 

1996 

Carabidae 

Perigona nigriceps (Dejean) Predator, in various environments South Asia Lucht, 1987 

Cerambycidae 

Gracilia minuta (F.) Xylophagous, polyphagous, often found in wicker Mediterranean region Lucht, 1987 

Nathrius brevipennis (Mulsant) Xylophagous, polyphagous, often found in wicker Mediterranean region Lucht, 1987 

Neoclytus acuminatus (F) Xylophagous, on Fraxinus, Ticino North America C. Besuchet, pers. comm. 

Phymatodes lividus (Rossi) Xylophagous, on broadleaved trees Mediterranean region C. Besuchet, pers. comm. 

Xylotrechus stebbingi Gahan Xylophagous, polyphagous, on aspen in Ticino Himalayas C. Besuchet, pers. comm. 

Cerylonidae 

Murmidius ovalis (Beck) Stored products, especially mouldy cereals, hay, Cosmopolitan C. Besuchet, pers. comm. 

etc. 

Chrysomelidae 

Diabrotica virgifera virgifera LeConte Pest on Maize, root feeder, Ticino Mexico, Central America Mario et al., 2001 

Leptinotarsa decemlineata (Say) Defoliator, pest on Solanaceae North America Lucht, 1987 

Cleridae 

Korynetes caeruleus (De Geer) Predator on anobiids in wood Cosmopolitan Lucht, 1987 

Necrobia ruficollis (F.) Domestic, insect predator Cosmopolitan Lucht, 1987 

Necrobia rufipes (De Geer) Domestic, in stored products, also predator Tropics, subtropics Lucht, 1987 

Necrobia violacea (L.) Mainly domestic, also on cadavers Cosmopolitan Lucht, 1987 

Tarsostenus univittatus (Rossi) Predator in wood, found in Genève only Cosmopolitan C. Besuchet, pers. comm.


Species 

Habitat – life traits Origin Reference for Switzerland 

Coccinellidae 

Harmonia axyridis (Pallas) Polyphagous predator (perhaps not yet established) East Asia Klausnitzer, 2004 

Rodolia cardinalis (Mulsant) 

Colydiidae 

Predator of scale insects, released and established 

in Ticino 

Australia C. Besuchet, pers. comm. 

Myrmecoxenus vaporariorum Guerin- 

Meneville 

Cryptophagidae 

In greenhouses, manure, compost, etc. Unclear Lucht, 1987 

Atomaria lewisi Reitter In decaying plant material East Asia Lucht, 1987 

Caenoscelis subdeplanata Brisout de 

Barneville 

Cucujidae 

In decaying wood and plant material North America C. Besuchet, pers. comm. 

Cryptolestes ferrugineus (Stephens) Stored products, mainly cereal grains Cosmopolitan Lucht, 1987 

Cryptolestes spartii (Curtis) Stored products Cosmopolitan C. Besuchet, pers. comm. 

Cryptolestes turcicus (Grouvelle) 

Curculionidae 

Domestic, on plant products Perhaps Turkey C. Besuchet, pers. comm. 

Pentarthrum huttoni Wollaston Decaying wood South-western Europe (native?) C. Besuchet, pers. comm. 

Sitophilus granarius (L.) Stored products India Lucht, 1987 

Sitophilus oryzae (L.) Stored products Asia Lucht, 1987 

Sitophilus zeamais Motschulsky 

Dermestidae 

Stored products Asia C. Besuchet, pers. comm. 

Anthrenus festivus Rosenhauer Domestic Mediterranean region C. Besuchet, pers. comm. 

Anthrenus flavipes LeConte Domestic, feeds on furnitures, fabrics, etc. Cosmopolitan (Mediterranean 

region?) 

C. Besuchet, pers. comm. 

Attagenus brunneus Faldermann Domestic Cosmopolitan (native?) C. Besuchet, pers. comm. 

Attagenus quadrimaculatus Kraatz Domestic Cosmopolitan (native?) C. Besuchet, pers. comm. 

Attagenus rossi Ganglbauer Domestic Cosmopolitan (native?) C. Besuchet, pers. comm. 

Attagenus smirnovi Zhantiev Domestic Cosmopolitan (native?) C. Besuchet, pers. comm. 

Attagenus unicolor (Brahm) Domestic, feeds mainly on fabrics Africa Lucht, 1987 

Dermester ater DeGeer Domestic, on animal products, fabrics, etc. Cosmopolitan (southern Europe?) C. Besuchet, pers. comm. 

Dermestes maculatus DeGeer Domestic, on animal products Cosmopolitan (North America?) Lucht, 1987 

Dermestes peruvianus La Porte de C. Domestic, on animal products, fabrics, etc. Central and South America C. Besuchet, pers. comm. 

Reesa vespulae (Milliron) Domestic and in museum collections North America C. Besuchet, pers. comm. 

Trogoderma angustum (Solier) Domestic and in museum collections South America C. Besuchet, pers. comm. 

Trogoderma glabrum Herbst Domestic and in nests of solitary wasps Cosmopolitan (native?) Lucht, 1987 

Trogoderma granarium Everts Stored products, especially cereals India C. Besuchet, pers. comm. 

Trogoderma versicolor (Creutzer) 

Histeridae 

Domestic and in museum collections Cosmopolitan Lucht, 1987 

Carcinops pumilio Erichson 

Hydrophilidae 

Predator on Diptera Cosmopolitan Lucht, 1987 

Cercyon laminatus Sharp In various humid environments East Asia Lucht, 1987 

Cryptopleurum subtile Sharp 

Languriidae 

In various humid environments East Asia Lucht, 1987 

Cryptophilus integer (Heer) On decaying plant material Cosmopolitan Lucht, 1987


Species 


Latridiidae 

Adistemia watsoni (Wollaston) Feeds on fungus, found in herbarium Cosmopolitan Lucht, 1987 

Corticaria ferruginea Marsham On fungus, on decaying plant material Cosmopolitan C. Besuchet, pers. comm. 

Corticaria fulva (Comolli) On fungus, on decaying plant material Cosmopolitan Lucht, 1987 

Corticaria pubescens Gyllenhal On fungus, on decaying plant material Cosmopolitan Lucht, 1987 

Corticaria serrata Paykull On fungus, on decaying plant material Cosmopolitan Lucht, 1987 

Dienerella filum (Aubé) On fungus, on decaying plant material Central America Lucht, 1987 

Lathridius minutus (L.) On fungus, on decaying plant material Cosmopolitan Lucht, 1987 

Migneauxia orientalis Reitter On fungus, on decaying plant material Mediterranean region C. Besuchet, pers. comm. 

Stephostetus (= Aridius) bifasciatus (Reitter) Feeds on fungus in various environments Australia C. Besuchet, pers. comm. 

Stephostetus nodifer (Westwood) Feeds on fungus in various environments New Zealand Lucht, 1987 

Thes bergrothi (Reitter) 

Lyctidae 

On fungus, on decaying plant material North-eastern Europe C. Besuchet, pers. comm. 

Lyctus africanus Lesne Domestic, in wood Africa C. Besuchet, pers. comm. 

Lyctus brunneus (Stephens) Domestic, in tropical wood South-east Asia Lucht, 1987 

Lyctus cavicollis Le Conte 

Merophysiidae 

Domestic, in wood North America C. Besuchet, pers. comm. 

Holoparamecus caularum (Aubé) 

Mycetophagidae 

On fungus, on decaying plant material Cosmopolitan C. Besuchet, pers. comm. 

Berginus tamarisci Wollaston Found on pine trees in Switzerland Canary Islands C. Besuchet, pers. comm. 

Litargus balteatus Le Conte On fungus, on decaying plants, e.g. cereals North America C. Besuchet, pers. comm. 

Typhaea stercorea (L.) 

Nitidulidae 

On fungus, on decaying plants, e.g. cereals North America Lucht, 1987 

Carpophilus dimidiatus (F.) On stored products and cultivated fields, mainly 

cereals 

North America C. Besuchet, pers. comm. 

Carpophilus hemipterus (L.) Feeds on fruits, dry fruits, cereals Cosmopolitan Lucht, 1987 

Carpophilus marginellus Motschulsky Mainly domestic, on cereals South-east Asia C. Besuchet, pers. comm. 

Carpophilus quadrisignatus Erichson Feeds on dry fruits Probably America C. Besuchet, pers. comm. 

Glischrochilus fasciatus (Olivier) Feeds on vegetables, fruits, etc. North America C. Besuchet, pers. comm. 

Glischrochilus quadrisignatus (Say) Feeds on vegetables, fruits, etc. North and Central America C. Besuchet, pers. comm. 

Urophorus rubripennis (Heer) 

Orthoperidae 

Under oak bark and on Apiaceae Perhaps Mediterranean region C. Besuchet, pers. comm. 

Orthoperus aequalis Sharp 

Ostomidae 

In compost, in Ticino Hawaii C. Besuchet, pers. comm. 

Tenebroides mauritanicus (L.) 

Ptiliidae 

On stored products, especially cereals Africa Lucht, 1987 

Acrotrichis insularis (Maeklin) In organic matters, from Vaud and Weissenstein North America C. Besuchet, pers. comm. 

Acrotrichis sanctaehelenae Johnson 

Ptilodactylidae 

In organic matters, Ticino St Helena, Africa? C. Besuchet, pers. comm. 

Ptilodactyla exotica Chapin 

Ptinidae 

Domestic, indoor plants North America C. Besuchet, pers. comm. 

Gibbium psylloides (Czempinski) Domestic, on stored products Cosmopolitan Lucht, 1987 

Niptus hololeucus (Faldermann) Domestic, feeds on fabrics Asia Minor, southern Russia Lucht, 1987


Species 


Ptinus tectus Boieldieu Domestic, on stored products Australia, New Zealand Lucht, 1987 

Epauloecus (=Tipnus) unicolor (Piller & Mitt.) In barns, cowshed, animal burrows, etc 

Scolytidae 

Cosmopolitan Lucht, 1987 

Gnathotrichus materiarius (Fitch) Xylophagous, on conifers North America Hirschheydt, 1992 

Phloeosinus aubei (Perris) Xylophagous, on Cupressaceae Mediterranean region Lucht, 1987 

Tripodendron laeve Eggers Xylophagous, on Picea East Asia, Scandinavia C. Besuchet, pers. comm. 

Xyleborinus alni (Niisima) Xylophagous, on broadleaved trees East Asia C. Besuchet, pers. comm. 

Xyleborus punctulatus Kurentzov Xylophagous, on broadleaved trees Siberia C. Besuchet, pers. comm. 

Xylosandrus germanus (Blandford) 

Silvanidae 

Xylophagous, polyphagous East Asia Lucht, 1987 

Ahasverus advena (Waltl) Feeds on fungus on rotten stored products South America Lucht, 1987 

Oryzaephilus mercator (Fauvel) On stored products, polyphagous Tropics C. Besuchet, pers. comm. 

Oryzaephilus surinamensis (L.) 

Staphylinidae 

On stored products, polyphagous Cosmopolitan Lucht, 1987 

Acrotona pseudotenera (Cameron) Mouldy hay East Asia C. Besuchet, pers. comm. 

Carpelimus zealandicus (Sharp) Sandy banks New Zealand C. Besuchet, pers. comm. 

Edaphus beszedesi Reitter Compost, rotting plant material Pehaps Mediterranean region Lucht, 1987 

Leptoplectus remyi Jeannel Unclear, found in Ticino Asia C. Besuchet, pers. comm. 

Lithocharis nigriceps (Kraatz) Compost, rotting plant material Asia Lucht, 1987 

Micropeplus marietti Jaquelin Du Val Waste land, fallow land Southern Europe, Caucasus C. Besuchet, pers. comm. 

Oligota parva Kraatz Domestic, in compost South America Lucht, 1987 

Oxytelus migrator (Fauvel) In compost, stable litter, etc. South East Asia C. Besuchet, pers. comm. 

Paraphloeostiba gayndahensis MacLeay Fermenting plant matters Australia C. Besuchet, pers. comm. 

Philonthus parcus Sharp In compost, stable litter, fermenting plant material, 

etc. 

East Asia C. Besuchet, pers. comm. 

Philonthus rectangulus Sharp In decomposing matters East Asia Lucht, 1987 

Philonthus spinipes Sharp In stable litter, cadavers, etc. East Asia C. Besuchet, pers. comm. 

Thecturota marchii (Dodero) Waste land, compost Southern Europe Lucht, 1987 

Trichiusa immigrata Lohse 

Tenebrionidae 

In compost and manure North America C. Besuchet, pers. comm. 

Alphitobius diaperinus (Panzer) In stored products, polyphagous Tropics C. Besuchet, pers. comm. 

Alphitophagus bifasciatus (Say) Mainly domestic, In rotten fruits Cosmopolitan C. Besuchet, pers. comm. 

Gnatocerus cornutus (F.) Stored products Central America Lucht, 1987 

Latheticus oryzae Waterhouse Stored products, cereals India C. Besuchet, pers. comm. 

Tenebrio molitor L., polyphagous Stored products Cosmopolitan Lucht, 1987 

Tribolium castaneum (Herbst) Stored products Cosmopolitan Lucht, 1987 

Tribolium confusum Jacquelin du Val Stored products Perhaps America, cosmopolitan Lucht, 1987 

Tribolium destructor Uyttenboogaart Stored products South America C. Besuchet, pers. comm. 

Tribolium madens Charpentier Stored products Cosmopolitan C. Besuchet, pers. comm.


Tab. 4.2 > Established alien insects in Switzerland: Lepidoptera. 

Species Habita – Life traits Origin References for Switzerland 

LEPIDOPTERA 

Arctiidae 

Hyphantria cunea (Drury) Polyphagous defoliator, in Ticino North America Rezbanyai-Reser, 1991; Jermini 

et al., 1995 

Gelechiidae 

Scrobipalpa ocellatella (Boyd) Defoliator/ borer on Chenopodiaceae, particularly on beet Southern Europe Karsholt and Razowski, 1996; 

CABI, 2001 

Sitotroga cerealella (Olivier) On stored products North America CABI, 2001 

Geometridae 

Eupithecia sinuosaria Eversmann On Chenopodium (not sure if established in Switzerland) Eastern Europe Rezbanyai-Reser et al., 1998 

Gracillariidae 

Cameraria ohridella Deschka & Dimic Leaf miner on Aesculus Unknown Kenis and Förster, 1998 

Caloptilia azaleella (Brants) Leaf miner on Rhododendron, in greenhouses EastAsia CSCF, unpublished list 

Parectopa robiniella Clemens Leaf miner on Robinia North America Sauter, 1983 

Phyllonorycter leucographella (Zeller) Leaf miner on Pyracantha and Crataegus East Mediterranean Region Sauter, 1983 

P. platani (Staudinger) Leaf miner on Platanus Balkans, Asia Minor M. Kenis, personal observation 

P. robiniella (Clemens) Leaf miner on Robinia North America M. Kenis, personal observation 

Lycaenidae 

Cacyreus marshalli (Butler) On Pelargonium, in Ticino South Africa Y. Gonzeth, pers. comm. 

Noctuidae 

Caradrina ingrata Staudinger Defoliator (not sure if established) East Mediterranean Region Rezbanyai-Reser L. 1983, 

Withebread, 1997 

Chrysodeixis chalcites Esper Vegetables, in glasshouses, migrant (not sure if established) 

Helicoverpa armigera (Hübner) Polyphagous defoliator, mainly in glasshouses (not sure if 

established) 

Mediterranean Region? Hächler et al., 1998 

Africa? Rezbanyai-Reser L. 1984, 

Hächler et al., 1998 

Sedina buettneri (Hering) Defoliator, mainly on Carex Siberia Blattner (1959) 

Psychidae 

Typhonia beatricis Hättenschwiler Polyphagous, in particular on mosses Eastern Mediterranean Hättenschwiler (2000) 

Pyralidae 

Cadra cautella (Walker) On stored products Africa Hoppe (1981) 

Ephestia elutella (Hübner) On stored products Cosmopolitan Hoppe (1981) 

E. kuehniella (Zeller) On stored products North and Central America Hoppe (1981) 

Plodia interpunctella (Hübner) On stored products Cosmopolitan Hoppe (1981) 

Sclerocona acutella (Eversmann) On Phragmites Siberia Grimm (1986) 

Saturniidae 

Samia cynthia walkeri (C. and R. Felder) Defoliator on Ailanthus East Asia CSCF, unpublished list 

Tineidae 

Monopis crocicapitella (Clemens) On fabrics Cosmopolitan CSCF, unpublished list 

Opogona sacchari (Bojer) Polyphagous pest in glasshouses Africa CABI, 2001 

Tortricidae 

Cydia molesta (Busck) Orchard pest, on Rosaceae East Asia CABI, 2001 

Yponomeutidae 

Argyresthia thuiella (Packard) Leaf miner on Cupressaceae North America Fischer (1993)


Tab. 4.3 > Established alien insects in Switzerland: Hymenoptera. 

Species Habitat – Life traits Origin References for Switzerland 

HYMENOPTERA 

Symphyta 

Siricidae 

Sirex cyaneus Fabricius Feeds on conifer trunks (mainly Abies) North America Pschorn-Walcher and Taeger, 1995 

Tenthredinidae 

Nematus tibialis Newman Defoliator on Robinia North America Liston, 1981, Pschorn-Walcher and 

Taeger, 1995 

Apocrita 

Aphelinidae 

Aphelinus mali (Haldeman) Parasitoid of Eriosoma lanigerum (Hausmann), introduced 


North America Greathead, 1976; Noyes, 2002 

Aphytis proclia (Walker) Parasitoid of scale insects, introduced in Italy Asia Greathead, 1976; Noyes, 2002 

Encarsia berlesei (Howard) 

Encarsia formosa Gahan 

Encarsia lounshuryi (Berlese & Paoli) 

Encarsia perniciosi (Tower) 

Braconidea 

Parasitoid of Pseudaulacaspis pentagona (Targioni- 

Tozzetti), introduced in Italy 

Biocontrol agent against whiteflies. Only in greenhouses 

Parasitoid of Chrysomphalus dictyospermi (Morgan), 

introduced in Italy 

Parasitoid of San José scale, introduced in Switzerland 

Aphidius colemani Viereck Biocontrol agent against aphids in greenhouses India 

Dryinidae 

East Asia 

South and Central America 

Madeira 

Probably Asia 

Mani et al., 1997 

Greathead, 1976; Noyes, 2002 

Greathead, 1976; Noyes, 2002 

Mani and Baroffio, 1997 

Neodryinus typhlocybae (Ashmead) Parasitoid of Metcalfa pruinosa Say, introduced in Ticino North America Jermini et al., 2000 

Encyrtidae 

Metaphycus helvolus (Compere) Biocontrol agent against scale insects. Only in greenhouses 

Ooencyrtus kuvanae (Howard) Parasitoid of Lymantria dispar L., introduced in Europe. 

Not reported from Switzerland but from all adjacent 

countries 

Formicidae 

South Africa Noyes, 2002 

East Asia Greathead, 1976; Noyes, 2002 

Hypoponera schauinslandi (Emery) Antropophilic, in greenhouses or other heated buildings. Unclear, tropics Neumeyer & Seifert, 2005 

Linepithema humile (Mayr) Various habitats indoors and outdoors, perhaps not 

established in Switzerland 

South America Kutter, 1981 

Monomorium pharaonis (L.) On stored products, antropophilic, mainly indoors South Asia Freitag et al., 2000 

Paratrechina longicornis (Latreille) 

Tapinoma melanocephalum (F.) 

Sphecidae 

Isodontia mexicana (Saussure) 

Sceliphron curvatum (F. Smith) 

Torymidae 

Omnivorous, antropophilic, found in Zürich airport in 

1999, perhaps not established 

On stored products, antropophilic, indoors only 

Predatory wasp, feeds on criquets, In Ticino 

Lemanic region 

Predatory wasp, anthropophilic 

Old world tropics 

Cosmopolitan, tropics 

Freitag et al., 2000 

Dorn et. al., 1997 

and North America Vernier, 1995, 2000 

Asia 

Gonseth & al. 2001 

Megastigmus spermotrophus Wachtl Feeds on seeds of Pseudotsuga North America Roques and Skrzypczynska, 2003 

Trichogrammatidae 

Trichogramma brassicae Bezdenko Biocontrol agent against Lepidoptera Eastern Europe Noyes, 2002


Tab. 4.4 > Established alien insects in Switzerland: Diptera. 

Species 

DIPTERA 

Agromyzidae 

Liriomyza huidobrensis (Blanchard) 

Liriomyza trifolii (Burgess) 

Napomyza gymnostoma (Loew) 

Calliphoridae 

Chrysomya albiceps (Wiedemann) 

Cecidomyiidae 

Rhopalomyia chrysanthemi (Ahlberg) 

Culicidae 

Habitat – Life traits Origin References for Switzerland 

Polyphagous leaf miner, pest in glasshouses 

Polyphagous leaf miner, pest in glasshouses in 

Europe, particularly on Chrysanthemum 

Leaf miner on Allium spp., especially onion and 

leek. 

On cadavers 

Pest on Chrysanthemum 

Aedes albopictus (Skuse) Human nuisance through its bites, and potential 

vector of various diseases 

Drosophilidae 

Chymomyza amoena (Loew) 

Drosophila curvispina Watabe & Toda 

Milichiidae 

Fruits of various broadleaved trees (apple, walnut, 

plum, etc.) 

Fruits 

Central and South America 

North America 

Unclear, perhaps indigenous 

CABI, 2001 

CABI, 2001 

Eder and Baur (2003) 

Cosmopolitan Rognes, 1997 

North America Skuhrava and Skuhravi 1997 

South-east Asia Unpublished information 

North America 

East Asia 

Burla and Bächli, 1992 

Bächli et al., 2002 

Desmometopa varipalpis Malloch Saprophagous/coprophagous Probably Cosmopolitan Merz et al., 2001 

Muscidae 

Hydrotaea aenescens (Wiedemann) On human or animal cadavers North America Merz et al., 2001 

Phoridae 

Dohrniphora cornuta (Bigot) Saprophagous, sometimes carnivorous Tropical, Cosmopolitan Prescher et al., 2002 

Stratiomyidae 

Hermetia illucens (L.) 

Tephritidae 

Bactrocera oleae (Gmel.) 

Ceratitis capitata (Wiedemann) 

Rhagoletis cingulata Curran 

Rhagoletis completa Cresson 

Ulidiidae 

Saprophagous, very abundant in Ticino. 

Fruit fly, on olive, in Ticino 

On various fruits, e.g. peach, apricot, peer, etc. 

Fruit fly, on cherry. First determined as R. indifferens 

Curran (B. Merz, pers. comm.) 

Fruit fly, on walnut 

North and South America , 

Africa 

Mediterranean region 

Africa 

North America 

North America 

Sauter, 1989 

Neuenschwander, 1984 

CABI, 2001 

Merz 1991, Mani et al., 1994 

Merz 1991, Mani et al, 1994 

Euxesta pechumani Curran In carrion and dung, in Ticino North America B. Merz., pers. comm.


Tab. 4.5 > Established alien insects in Switzerland: Hemiptera. 

Species 

Host plant Origin Reference for Switzerland 

HEMIPTERA 

Sternorrhyncha 

APHIDINA 

Adelgidae 

Dreyfusia nordmannianae (Eckstein) On Abies Caucasus Eichhorn, 1967 

Dreyfusia prelli Grosmann On Abies Caucasus Eichhorn, 1967 

Eopineus strobus (Hartig) On Pinus strobus L., Picea spp. Not recorded but 

probably in Switzerland 

North America Schwenke, 1972 

Gilletteella cooleyi (Gillette) 

Aphididae 

On Picea and Pseudotsuga North America Forster, 2002 

Acyrthosiphon caraganae (Choldokovsky) On Caragana and other Fabaceae Siberia CSCF/Lampel, unpublished list 

Aphis forbesi Weed On strawberry North America Meier, 1975 

Aphis gossypii Glover Polyphagous, mainly Cucurbitaceae and Malva- Cosmopolitan, tropical CABI, 2001 

ceae, in greenhouses in Central Europe 

regions 

Aphis spiraecola Patch Polyphagous, e.g. Citrus, apple East Asia Hohn et al., 2003 

Aphis spiraephaga F.P. Müller On Spiraea Central Asia Stary, 1995 

Appendiseta robiniae (Gillette) On Robinia North America Lethmayer and Rabitsch, 2002 

Aulacorthum circumflexum (Buckton) Polyphagous, in greenhouses South East Asia CSCF/Lampel, unpublished list 

Elatobium abietinum (Walker) On Picea North America CABI, 2001 

Idiopterus nephrelepidis Davis On ferns, mostly indoors Neotropics CSCF/Lampel, unpublished list 

Illinoia azaleae (Mason) On Rhododendron and other Ericaceae North America CSCF/Lampel, unpublished list 

Illinoia lambersi (Mac Gillivray) On Rhododendron and Kalmia North America CSCF/Lampel, unpublished list 

Impatientinum asiaticum Nevsky On Impatiens Central Asia CSCF/Lampel, unpublished list 

Macrosiphoniella sanborni (Gillette) On Chrysanthemum East Asia Meier, 1972 

Macrosiphum albifrons Essig On Lupinus North America CSCF/Lampel, unpublished list 

Macrosiphum euphorbiae (Thomas) Polypgagous, on vegetables North America Derron and Goy, 1995 

Megoura lespedezae (Essig & Kuwana) On Lespedeza, Japanese clover East Asia Giacalone & Lampel, 1996 

Microlophium primulae (Theobald) On Primula Asia CSCF/Lampel, unpublished list 

Myzus ascalonicus Doncaster On Allium spp. Near East CSCF/Lampel, unpublished list 

Myzus cymbalariae Stroyan 

Polyphagous Not clear. In UK, South Meier, 1972 

(=cymbalariellus Str.) 

Africa, New Zealand and 

Australia 

Myzus ornatus Laing On Prunus cornuta (Wallich ex Royle) (primary 

host) and many herbaceous plants (secondary 

hosts 

Himalaya CSCF/Lampel, unpublished list 

Myzus persicae (Sulzer) Polyphagous Cosmopolitan, probably from 

Asia 

CABI, 2001 

Myzus varians Davidson On Clematis East Asia Giacalone & Lampel, 1996 

Nearctaphis bakeri (Cowen) Maloideae (primary hosts) and Fabaceae (secondary 

hosts) 

North America CSCF/Lampel, unpublished list 

Pentatrichopus fragaefolii (Cockerell) On strawberry North America CSCF/Lampel, unpublished list 

Rhodobium porosum (Sanderson) On Rosa, in greenhouses in Central Europe Tropics and subtropics Meier, 1972 

Rhopalosiphoninus latysiphon (Davidson) Polyphagous North America CSCF/Lampel, unpublished list 

Rhopalosiphum maidis (Fitch) On Maize, Sorghum, sugar cane and other 

Poaceae 

Probably Asia Meier, 1975


Species 


Toxoptera aurantii (Boyer de Fonscolombe) Polyphagous, in Europe mainly on Citrus Cosmopolitan, tropics and 

subtropics 

CSCF/Lampel, unpublished list 

Uroleucon erigeronense (Thomas) 

Callaphididae 

On Asteraceae (Erigeron, Coniza, etc.) North America CSCF/Lampel, unpublished list 

Myzocallis (=Lineomyzocallis) walshii 

(Monell) 

On Quercus North America Giacalone and Lampel (1996) 

Takecallis arundicolens (Clarke) On bamboo South East Asia Lampel and Meier (2003) 

Takecallis arundinariae (Essig) On bamboo South East Asia Giacalone and Lampel (1996) 

Takecallis taiwanus (Takahashi) On bamboo South East Asia Giacalone and Lampel (1996) 

Tinocallis nevskyi Remaudière, Quednau & 

Heie 

Chaitophoridae 

On Ulmus Western Asia Giacalone and Lampel (1996) 

Periphyllus californiensis (Shinji) 

Pemphigidae 

On Acer East Asia Lampel and Meier (2003) 

Eriosoma lanigerum (Hausmann) 

Lachnidae 

On orchard trees North America CPC 

Cinara cupressi (Buckton) 

Phylloxeridae 

On Cupressaceae North America? Taxonomy 

confusing 

Lampel, 1974. Watson et al., 

1999 

Viteus vitifoliae (Fitch) 

PSYLLINA 

Psyllidae 

On grapevine North America CPC 

Acizzia jamatonica (Kuwayama) On Albizia julibrissin Durazz East Asia D. Burckhardt, pers. comm. 

Bactericera trigonica Hodkinson On Daucus carota L. Mediterranean region Burckhardt and Freuler, 2000 

Cacopsylla fulguralis (Kuwayama) On Elaeagnus East Asia D. Burckhardt, pers. comm. 

Cacopsylla pulchella (Löw) On Cercis siliquastrum L. Mediterranean region Burckhardt and Freuler, 2000 

Camarotoscena speciosa (Flor) On Populus. Maybe natural spread Probably Mediterranean 

region, or Asia 

Burckhardt and Freuler, 2000 

Ctenarytaina eucalypti (Maskell) On Eucalyptus Australia D. Burckhardt, pers. comm. 

Homotoma ficus (L.) On Ficus carica L. Mediterranean region and 

Middle East 

Burckhardt and Freuler, 2000 

Livilla spectabilis (Flor) On Spartium junceum L. Mediterranean region Schaefer, 1949 

Livilla variegata (Löw) On Laburnum Southern Europe Schaefer, 1949 

Phyllopecta trisignata (Löw) On Rubus fruticosus L. Maybe natural spread Southern Europe, Near East Schaefer, 1949 

Spanioneura fonscolombii Foerster 

Triozidae 

On Buxus sempervirens L. Maybe natural spread Mediterranean region Schaefer, 1949 

Trioza alacris Flor On Laurus nobilis L. Mediterranean region to 

Caucasus 

Schaefer, 1949 

Trioza centranthi (Vallot) 

ALEYRODINA 

Aleyrodidae 

On Centranthus rubber (L.) Mediterranean region Schaefer, 1949 

Bemisia tabaci (Gennadius) Polyphagous, in greenhouse Cosmopolitan, probably Asia CABI, 2001 

Trialeurodes vaporariorum Westwood 

COCCINA 

Diaspididae 

Polyphagous, in greenhouse Central America CABI, 2001 

Aonidia lauri (Bouché) Polyphagous, on ornamentals Mediterranean region Kozar et al., 1994


Species 


Diaspidiotus distinctus (Leonardi) On Corylus, Matricaria and Quercus Mediterranean region. Maybe 

indigenous 

Kosztarab and Kozar, 1988 

Diaspidiotus osborni (Newell & Cockerell) On Platanus, Corylus and Gleditsia North America Kozar et al., 1994 

Dynaspidiotus britannicus (Newstead) Polyphagous, indoors and outdoors Unclear Kozar et al., 1994 

Pseudaulacaspis pentagona (Targioni- 

Tozzetti) 

Polyphagous, on ornamental and orchard trees East Asia Mani et al., 1997 

Quadraspidiotus labiatarum (Marshal) Polyphagous Mediterranean region. Maybe 


Kozar et al., 1994 

Quadraspidiotus lenticularis (Lindinger) Polyphagous on broadleaved trees Mediterranean region. Maybe 



Quadraspidiotus perniciosus (Comstock) Polyphagous, pest in orchards East Asia Mani and Baroffio, 1997 

Quadraspidiotus pyri (Lichtenstein) 

Ortheziidae 

Polyphagous, pest of fruit trees Mediterranean region. Maybe 



Orthezia insignis Browne 

Pseudococcidae 

Polyphagous, in greenhouses Neotropics Kozar et al., 1994 

Peliococcus multispinus (Siraiwa) On Thymus East Asia, Caucasus? Kozar et. al, 1994 

Planococcus citri (Risso) Polyphagous, in greehouses and on indoor plants Tropics and subtropics Kozar et. al, 1994 

Trionymus penium (Williams) 

Coccidae 

On Pseudosasa South-east Asia Kozar et. al, 1994 

Chloropulvinaria floccifera (Westwood) Polyphagous Mediterranean region or East 

Asia? 


Coccus hesperidum L. Polyphagous, indoors and outdoors Cosmopolitan, but prob. not 

from Europe 


Eupulvinaria hydrangeae (Steinweden) Polyphagous on broadleaved trees Perhaps East Asia Kozar et al., 1994 

Pulvinaria regalis Canard 

Margarodidae 

Polyphagous on broadleaved trees Perhaps East Asia Kozar et al., 1994 

Icerya purchasi Maskell 

Auchenorrhyncha 

Cicadellidae 

Polyphagous, indoors and outdoors in Switzerland Australia Kozar et al., 1994 

Edwardsiana platanicola (Vidano) On Platanus Unknown. Introduced from 

Northen Italy 

Günthart, 1987 

Eupteryx decemnotata Rey On Salvia Southern Europe Günthart, 1987 

Graphocephala fennahi Young On Rhododendron North America Günthart, 1987 

Orientus ishidae (Matsumura) On Salix and Betula East Asia Günthart et al., 2004 

Scaphoideus titanus Ball 

Flatidae 

On vine, vector of ‘flavescence dorée’ North America Günthart, 1987 

Metcalfa pruinosa Say 

Membracidae 

Polyphagous North America Bonavia and Jermini, 1998 

Stictocephala bisonia Kopp & Yonke 

Heteroptera 

Lygaeidae 

Polyphagous North America Günthart, 1987 

Arocatus longiceps Stal On Platanus Mediterranean region, 

perhaps expanding naturally 

Giacalone et al., 2002 

Orsillus depressus Dallas On Cupressaceae Mediterranean region, 


R. Heckmann, pers. comm.


Species 


Oxycarenus lavaterae (F.) 

Miridae 

On Malvaceae and Tiliaceae Mediterranean region, 


R. Heckmann, pers. comm. 

Deraeocoris flavilinea (A. Costa) 

Tingidae 

Predator on aphids on broead-leaved trees Mediterranean Region, 


Rabitsch, 2002 

Corythucha arcuata (Say) On Quercus North America Meier et al., 2004 

Corythucha ciliata (Say) On Platanus North America Barbey, 1996 

Tab. 4.6 > Established alien insects in Switzerland: Orthoptera, Dictyoptera, Thysanoptera, Psocoptera, Syphonaptera and Anoplura. 

Species 


ORTHOPTERA 

Gryllidae 

Acheta domesticus (L.) 

Rhaphidophoridae 

Omnivorous, synanthropic, also ouside in the 

Valais 

North Africa, Cosmopolitan Thorens and Nadig, 1997 

Tachycines asynamorus Adelung 

DICTYOPTERA 

Blattellidae 

Omnivorous, greenhouses and botanical gardens Cosmopolitan, probably from 

East Asia 

Thorens and Nadig, 1997 

Blattella germanica (L.) Omnivorous, synanthropic Cosmopolitan Landau et al., 1999 

Supella longipalpa (F.) 

Blattidae 

Omnivorous, synanthropic Africa Landau et al., 1999 

Blatta orientalis L. Omnivorous, synanthropic Cosmopolitan, possibly 


Landau et al., 1999 

Periplaneta americana (L.) Omnivorous, synanthropic Africa, cosmopolitan, Landau et al., 1999 

Periplaneta australasiae (F.) 

THYSANOPTERA 

Thripidae 

Omnivorous, synanthropic Cosmopolitan, tropics and 

subtropics 

Landau et al., 1999 

Frankliniella intonsa (Trybom) Polyphagous, mainly in greenhouses East Asia CABI, 2001, Linder et al., 1998 

Frankliniella occidentalis (Pergande) Polyphagous, mainly in greenhouses North America. Now cosmopolitan 

CABI, 2001, Ebener et al., 1989 

Heliothrips haemorrhoidalis (Bouché) Polyphagous, in greenhouses Probably tropical America. 

Now cosmopolitan 

CABI, 2001 

Thrips simplex (Morison) 

PSOCOPTERA 

Trogiomorpha 

Trogiidae 

Develops on Gladiolus, but found also on many 

other plants, in greenhouses 

Probably South Africa CABI, 2001 

Cerobasis annulata (Hagen) Domestic Unclear (see text) Lienhard, 1994 

Lepinotus inquilinus von Heyden Domestic, rarely outdoors Unclear (see text) Lienhard, 1994


Species 


Lepinotus patruelis Pearman Domestic, rarely outdoors Unclear (see text) Lienhard, 1994 

Lepinotus reticulatus Enderlein Domestic, occasionally outdoors Unclear (see text) Lienhard, 1994 

Trogium pulsatorium (L.) Domestic Unclear, perhaps Mediterranean 

region (see text) 

Psyllipsocidae 

Dorypteryx domestica (Smithers) 

Dorypteryx longipennis Smithers 

Dorypteryx pallida Aaron 

Psyllipsocus ramburii Sélys-Longchamps 

Troctomorpha 

Liposcelididae 

Domestic 

Domestic 

Domestic 

Domestic and in caves 

Unclear, perhaps Africa (see 

text) 

Unclear (see text) 

Unclear, perhaps North 

America (see text) 


Lienhard, 1994 





Liposcelis bostrychophila Badonnel Domestic, occasionally outdoors Unclear (see text) Lienhard, 1994 

Liposcelis brunnea Motschulsky Domestic, occasionally outdoors Unclear (see text) Lienhard, 1994 

Liposcelis corrodens (Heymons) Domestic, occasionally outdoors Unclear (see text) Lienhard, 1994 

Liposcelis decolor (Pearman) Domestic, occasionally outdoors Unclear (see text) Lienhard, 1994 

Liposcelis entomophila (Enderlein) Domestic Unclear (see text) Lienhard, 1994 

Liposcelis mendax Pearman 

Liposcelis pearmani Lienhard 

Domestic 

Domestic, occasionally outdoors 

Unclear, perhaps Asia (see 

text) 




Liposcelis pubescens Broadhead Domestic Unclear (see text) Lienhard, 1994 

Sphaeropsocidae 

Badonnelia titei Pearman Domestic Unclear (see text) Lienhard, 1994 

Psocomorpha 

Ectopsocidae 

Ectopsocus pumilis (Banks) 

Ectopsocus richardsi (Pearman) 

Ectopsocus vachoni Badonnel 

SIPHONAPTERA 

Pulicidae 

Ctenocephalides felis felis 

Spilopsylus cuniculi (Dale) 

ANOPLURA 

Hoplopleuridae 

Domestic 

Domestic 

Domestic 

(Bouché) Ectoparasite on cat and, occasionally, other 

carnivores 

Ectoparasite on rabbit and, occasionally, other 

mammals 


text) 


text) 

Unclear, perhaps Mediterranean 

region (see text) 

Cosmopolitan, probably not 

Europe 

Probably Iberian Peninsula 




Beaucournu and Launay (1990) 

Beaucournu and Launay (1990) 

Haemodipsus ventricosus (Denny) Ectoparasite on rabbit Probably Iberian Peninsula Büttiker and Mahnert (1978)

5 > Spiders and Allies – Arachnida 101 

5 > Spiders and Allies – Arachnida 

Prepared by Theo Blick, Ambros Haenggi and Rüdiger Wittenberg 

5.1 Introduction 

This chapter summarizes the available information on Arachnida, except Acari, covering 

species’ distribution, biology, and potential harm to the environment and economy. 

Since knowledge of the natural distribution, origins and movement for the Arachnida is 

very limited, it was decided to use specific definitions for the terms described below, 

so that coverage of invasive species is expanded to include native species which are 

spreading, thereby not discriminating between natural spread and human-mediated 

expansion. The following definitions characterize the framework for this chapter, and 

explain which species are covered and which are not. 

> Neozoa (Geiter et al., 2002): A neozoan animal has been introduced, by direct or 

indirect human mediation, to a region to which it is not native and has established a 

population there. 

> Invasive Species (Geiter et al., 2002): This term does not discriminate between 

natural and human-mediated colonization of a new territory and focuses on species 

causing problems. 

The spiders discussed in this report are categorized mainly by habitat and biology, as 

follows: 

> Species of natural habitats: spiders and their relatives which live in natural, nearnatural 

or human-influenced habitats (e.g. crop fields), but not in close proximity to 

human buildings. The report focuses on species which have changed their distribution, 

mainly during the last two decades because of a lack of older data. It is based 

on pitfall trap results, since continuous and standardized information on orb web 

species is not available. 

> Species inside, and in close proximity, to human buildings: spiders and their 

relatives which typically inhabit walls of buildings or live in direct contact with humans, 

and which have expanded their distribution range into Central Europe during 

recent decades. 

> House-dwelling species: spiders and their relatives which exclusively occur in 

buildings, and no populations in natural habitats are known. 

> Greenhouse-inhabiting species: spiders and their relatives which, in Central 

Europe, exclusively inhabit greenhouses and other similarly warm buildings. They 

have established populations in these warm environments, but cannot survive out-


side due to their climatic requirements. They can also be introduced into houses, e.g. 

with flowers (e.g. Eperigone eschatological (Crosby)). 

> ‘Banana spiders’: spiders which are introduced with fruit commodities, especially 

bananas. They are often rather spectacular individuals, but they are not able to establish 

in our climate. 

> Terrarium species: spiders, mostly tarantulas/theraphosids (so-called ‘bird-eating 

spiders’) from warm regions, which escape captivity, but cannot breed in the Central 

European climate and at the most survive until the following winter. 

The orders Araneae (spiders), Opiliones (harvestmen) and Pseudoscorpiones (false 

scorpions) within the class Arachnida are covered in this report. Acari (ticks and 

mites), although very important for the agricultural and the health sectors, are not 

included in this review, because of the difficulties of preparing comprehensive lists and 

their minor relevance for the environmental sector. Species which were introduced to 

Switzerland more than a few decades ago are not included, because of their largely 

unresolved status. Thus, the wasp spider (Argiope bruennichi (Scopoli)) is not included 

in the list. Additionally, species which besides inhabiting houses and basements also 

live in caves, rock screes, walls in vineyards or quarries, as for example the genus 

Pholcus or the jumping spider Salticus scenicus (Clerck), are not discussed here. 

The main general literature sources for the report are Thaler and Knoflach (1995), 

Geiter et al. (2002) and Komposch (2002). 

Knowledge about synanthropic spiders and their relatives in Switzerland is extremely 

limited. Therefore many observations discussed in the report are based on knowledge, 

although likewise rudimentary, accumulated in other Central European countries, and 

extrapolated to Switzerland. The situation in these countries will be similar to that in 

Switzerland and including the information gives a more comprehensive picture of the 

alien spider fauna of Central Europe. 

Generally, synanthropic spiders seem to attract less attention than species inhabiting 

natural habitats even among arachnologists or, rather, little is published about them. 

The spitting spider Scytodes thoracica (Latr.) is an example of a spider almost exclusively 

found in houses in Central Europe; its distribution is fairly well-known by 

arachnologists, but there are few publications about it. The same is true for species of 

the genus Araneus, which frequently occur in houses and gardens. 

5.2 List of species 

Table 5.1 introduces the species mentioned in this report.


Tab. 5.1 > Species mentioned in this report, named after Platnick (2004). 

Species name Author, Year Family Habitat 

Achaearanea tabulata * Levi, 1980 Theridiidae In houses 

Artema atlanta * Walckenaer, 1837 Pholcidae In houses 

Astrobunus laevipes * (Canestrini, 1872) Phalangiidae Natural 

Chelifer cancroides (L., 1758) Cheliferidae In houses 

Cicurina japonica (Simon, 1886) Dictynidae Natural 

Coleosoma floridanum Banks, 1900 Theridiidae Greenhouses 

Collinsia inerrans (O. P.-Cambridge, 1885) Linyphiidae Natural 

Dasylobus graniferus (Canestrini, 1871) Phalangiidae Natural 

Dictyna civica (Lucas, 1850) Dictynidae On buildings 

Diplocephalus graecus * (O. P.-Cambridge, 1872) Linyphiidae Natural 

Eperigone eschatologica (Crosby, 1924) Linyphiidae Greenhouses 

Eperigone trilobata (Emerton, 1882) Linyphiidae Natural 

Erigone autumnalis Emerton, 1882 Linyphiidae Natural 

Harpactea rubicunda (C.L. Koch, 1838) Dysderidae In houses, but also natural 

Hasarius adansoni (Audouin, 1826) Salticidae Greenhouses 

Heteropoda venatoria (L., 1767) Sparassidae Greenhouses 

Holocnemus pluchei (Scopoli, 1763) Pholcidae In houses 

Micropholcus fauroti * (Simon, 1887) Pholcidae In houses 

Nesticus eremita Simon, 1879 Nesticidae Natural 

Oecobius maculatus Simon, 1870 Oecobiidae Natural 

Opilio canestrinii (Thorell, 1876) Phalangiidae On buildings 

Ostearius melanopygius (O. P.-Cambridge, 1879) Linyphiidae Natural 

Pseudeuophrys lanigera (Simon, 1871) Salticidae On buildings 

Psilochorus simoni (Berland, 1911) Pholcidae In houses 

Thanatus vulgaris * Simon, 1870 Philodromidae Greenhouses 

Uloborus plumipes Lucas, 1846 Uloboridae Greenhouses 

Zodarion italicum (Canestrini, 1868) Zodariidae Natural 

Zodarion rubidum Simon, 1914 Zodariidae Natural 

Zoropsis spinimana (Dufour, 1820) Zoropsidae In houses 

*Species not yet recorded from Switzerland. 

5.3 Species of natural habitats 

Eperigone trilobata (Emerton) 

This spider has a wide distribution range in North America (Millidge, 1987) and was 

first recorded from Europe in the 1980s at Karlsruhe, Germany. A catalogue of Swiss 

spiders (Maurer and Hänggi, 1990) noted several records from the Swiss cantons Jura 

and Ticino. This species is a common member of the spider fauna in all open habitats 

(e.g. Blick et al., 2000) and was first recorded in the Jura in 1999 at about 800 m above 

sea level (T. Blick, unpubl.).


Fig. 5.1 > Records of Eperigone trilobata (left) and Zodarion italicum (right) in Germany 

and north-west Switzerland. 

After Staudt (2004). 

(green dots: since 2000, grey dots: 1990–1999, red dots: 1980–1989) 

In Germany, this species has spread from Baden-Württemberg, where it was first 

found, to Hessen and Rheinland-Pfalz and into north-western Bayern (Staudt, 2004: see 

Fig. 5.1). There are also records from outside this area, i.e. in the east of Bayern and 

the south of Niedersachsen (T. Blick, unpubl.; pers. comm. of various arachnologists – 

these data are not included in Fig. 5.1). The data presented above indicate that this 

species will colonize Central Europe in the foreseeable future. However, it is unclear 

what the altitude limit will be or whether its frequency in samples will increase. During 

past years, there has been no indication that the frequency of the species is increasing – 

to the contrary, investigations on the same field site in 1994 and 1999 showed a decrease 

in numbers of the species (Baur et al., 1996; Hänggi and Baur, 1998; Blick, 

unpubl.). In most samples the frequency of the species reached only about 5 % – the 

maximum was 30 % at Basel railway station in 2002 (Hänggi and Heer, unpubl.). 

Displacement of native spider species has not been recorded and would be very difficult 

to prove. Such studies would involve standardized experiments at the same field 

site over decades, with year-round sampling and also Swiss-wide sites for comparative 

work. Funding for this kind of research seems unlikely, although the samples could be 

used for other arthropod research.


Zodarion italicum (Canestrini) 

The origin of the aptly named Zodarion italicum is the south of Europe. It has expanded 

its distribution since the publication of the catalogue of Swiss spiders (Maurer 

and Hänggi, 1990 – cited as sub Z. gallicum), and has since reached the south of Switzerland. 

It is possible that it is even native to that region (see, e.g., Lessert, 1910). This 

spider is a highly specialized predator of ants (Pekar and Kral, 2002) and occurs mainly 

in open habitats. The rapid expansion of its range is probably attributable to humanmediated 

transport to new areas and to global warming, which allows species of southern 

origin to survive north of the Alps. However, this probable relationship would be 

difficult to demonstrate. The species is also expanding its range in Germany, as is its 

sister species Z. rubidium Simon (see Bosmans, 1997; Staudt, 2004; also see Figure 

5.1). 

Other species found in natural habitats 

Besides the two species mentioned above, a number of other species are spreading in 

Central Europe, or their spread is likely within the next few years. A selection of these 

species is discussed below. 

> Collinsia inerrans (O.P.-Cambridge) (syn. Milleriana inerrans, C. submissa) has 

been found locally in Switzerland during the last 50 years. Currently, the species is 

expanding its range in western Germany (Klapkarek and Riecken, 1995), and has 

reached the north-east of Bayern (Blick, 1999). However, it has not yet reached the 

abundance of Eperigone trilobata, despite their similarities in size and ecological 

niche. The future expansion of this species in Switzerland should be monitored. 

> Ostearius melanopygius (O.P.-Cambridge): Ruzicka (1995) portrays the spread of 

this cosmopolitan species of unknown origin (cryptogenic) in Europe. In Switzerland, 

a similar pattern as for C. inerrans has been observed. However, occasionally 

the species exhibits mass outbreaks, which can be a nuisance to humans although it 

does no actual harm (Sacher, 1978); for cases in Switzerland see, e.g., Benz et al. 

(1983). The normal sampling techniques using traps at ground level are not effective 

under these circumstances and generally catch only single individuals. The reasons 

for the mass outbreaks are not yet understood. 

> The distribution of Harpactea rubicunda (C.L. Koch) described by Wiehle (1953) 

was restricted to the eastern part of Germany at that time. Since then, the species has 

expanded its range considerably westwards, most probably by human-mediated 

transport. It occurs in houses as well as in other synanthropic habitats. In Switzerland, 

the species was found near Zurlinden (Hänggi, 1988) and in a disused railway 

area at Basel (Hänggi and Weiss, 2003). 

> Erigone autumnalis Emerton, like Eperigone trilobata, originates in North America. 

The species has been found at several locations in Switzerland (Maurer and 

Hänggi, 1990; Hänggi, unpubl.). However, it seems to be less abundant and covers a 

smaller range than E. trilobata. 

> Nesticus eremita Simon can be found outdoors around Basel (Hänggi and Weiss, 

2003; Hänggi, unpubl.), whereas further north the species is restricted to underground 

canals and artificial caves (Jäger, 1995, 1998; Blick, unpubl.). It is very


likely that this southern European species will expand its range further in the near 

future. 

> Cicurina japonica (Simon): this spider of Japanese–Chinese origin was not accepted 

as an established spider species in Germany by Platen et al. (1995), since the introduction 

of the species near Kehl am Rhein was thought to be temporary. Since then, 

fairly large populations have been found in the area around the railway at Basel 

(Hänggi and Heer, unpubl.). This indicates that the species is able to establish in 

Europe and the further development of its populations should be monitored. 

> Diplocephalus graecus (O.P.-Cambridge): Blick et al. (2000) presents a record of 

this species of Mediterranean origin from agricultural areas near Paris, France. Today 

the species has reached Belgium (Bonte et al., 2002), so it is very likely that it 

will expand its range into most of Central Europe, including Switzerland, in the near 

future. 

> Dasylobus graniferus (Canestrini) (syn. Eudasylobus nicaeensis): Martens (1978) 

mentions records of this harvestman species from southern Switzerland. However, in 

1997 more than 100 individuals were collected near Liestal (canton Baselland) (I. 

Weiss, unpubl.). Thus, an expansion into Central Europe of this southern European 

species is expected, but will probably be difficult to document, since almost no research 

on harvestmen distribution is being carried out in Switzerland or in adjacent 

areas of Germany. 

> Another harvestman, Astrobunus laevipes (Canestrini), is already in an expansion 

phase in Central Europe (see Höfer and Spelda, 2001), especially along rivers. It 

reached the Netherlands recently (Wijnhoven, 2003). There are no records for Switzerland 

yet. However, its taxonomic differentiation from A. bernardinus Simon, 

known from the Jura, would merit attention (see Höfer and Spelda, 2001). 

Any estimation of potential impacts of the species discussed above would only be 

guesswork. Economic damage can reasonably be excluded, but it is possible that native 

species would be replaced or at least populations reduced due to the invaders. However, 

testing this hypothesis would necessitate long-term monitoring studies in the field 

on established plots. These investigations are not being carried out to the knowledge of 

the authors. 

5.4 Species in, and in close proximity to, human buildings 

Only a few members of the Arachnida are restricted to the outside of houses and other 

human-made structures, although there are native species naturally occurring on rocks 

and tree bark. The species which have expanded their range in recent decades are 

discussed below: 

> Dictyna civica (Lucas) inhabits walls of houses particularly in warm climates 

(Braun, 1952; Billaudelle, 1957; van Keer and van Keer, 1987). The species is considered 

to be a nuisance by owners of houses in the lowland parts of Switzerland as 

well as in the Rhine valley in Baden-Württemberg (Stächele, 2002).


> Pseudeuophrys lanigera (Simon) (syn. Euophrys lanigera) is a good example of a 

spider which has been continuously expanding its range in Central Europe in recent 

decades (Braun, 1960; Wijnhoven, 1997; Staudt 2004). Although Maurer and 

Hänggi (1990) listed only a few sites for this species in Switzerland, it is likely to 

expand its range in the near future. It is not known whether the species is replacing 

or influencing the population of native jumping spiders with similar ecological 

niches on house walls, e.g. Salticus scenicus. 

> The harvestman Opilio canestrinii (Thorell) has established populations on walls of 

houses in Central Europe (Enghoff, 1987; Bliss, 1990; Gruber, 1988; Malten, 1991; 

van der Weele, 1993). However, records of natural populations, i.e. on bark of trees, 

have been documented since then (e.g. Staudt, 2004). As the monitoring of harvestmen 

distribution and ecology in Switzerland is minimal, there are almost no data 

available from Switzerland on this species (Martens, 1978: sub O. ravennae). 

House-dwelling species 

Spiders living in residential houses have either adapted from native natural habitats 

such as tree bark, caves and cliffs, or have been introduced from southern Europe and 

become established. Sacher (1983) gives an overview of spiders living in houses. Some 

additional house-dwelling species are occasionally observed (Hänggi, 2003), e.g. 

Achaearanea tabulata Levi in Austria and Germany (see Knoflach, 1991; Thaler and 

Knoflach, 1995), and therefore this species is likely to be found in Switzerland in the 

future. However, with the exception of Zoropsis spinimana (Dufour), which is discussed 

below, no house-dwelling species is showing signs of being invasive. 

Zoropsis spinimana (Dufour) 

The first record of Z. spinimana was an individual caught in 1994 in a residential house 

in Basel (Hänggi, 2003). Since then other records have been reported from houses in 

the south of Switzerland (Ticino). Observations in Austria (Thaler and Knoflach, 1998) 

suggest this species could cause problems, as it is one of the very few spiders in Central 

Europe which can penetrate the human skin with its cheliceres and produce a 

painful bite (Hansen, 1996). This species has not (yet) been recorded from Germany 

(Blick et al., 2002). 

Other species of house-dwelling spiders and their relatives 

Some other spider species living in houses are currently found more regularly in Central 

Europe, e.g. Psilochorus simoni (Berland). These species do expand their range, 

but are found only in small numbers or as individuals. More invaders can be expected, 

in particular in the family Pholcidae (daddy long legs spiders). This is indicated by 

observations in the harbour at Antwerpen, Belgium (van Keer and van Keer, 2001), 

where the introduced Artema atlanta Walckenaer and Micropholcus fauroti (Simon)


have become established, and from German cities, where stable populations of 

Holocnemus pluchei (Scopoli) have been found (Jäger, 1995, 2000). 

Interestingly, in contrast to the expanding nature of many house-dwelling species, the 

false scorpion Chelifer cancroides (L.) seems to be decreasing in abundance, although 

the distribution and population sizes of this group are very poorly investigated in 

Switzerland, especially in synanthropic areas. Apparently, the increased hygiene and 

the changed climate in houses caused by central heating affects this species. The 

considerable alteration in temperature, and changes in daily temperature and humidity, 

might favour some species, especially species adapted to a warm environment, and 

negatively affect others. 

5.5 Greenhouse-inhabiting species 

> Hasarius adansoni (Audouin) is a cosmopolitan species, which is widespread in 

European greenhouses (Simon, 1901; Holzapfel, 1932; König and Pieper, 2003). 

Records from Switzerland are summarized by Hänggi (2003). Information on synanthropic 

spiders in general, and this species in particular, is too limited to come to any 

conclusion about the status of species, e.g. whether populations are increasing. 

> Uloborus plumipes Lucas is another greenhouse species, but is much more common 

than the species above (Jonsson, 1993, 1998; Thaler and Knoflach, 1995). However, 

misidentifications in some records arising from confusion with the congeneric 

U. glomosus (Walckenaer) cannot be ruled out. 

> The first record of Coleosoma floridanum Banks in Switzerland was reported by 

Knoflach (1999) from the tropical greenhouse of the Old Botanical Garden at Basel. 

This pantropical species is occasionally reported from greenhouses in Europe 

(Hillyard, 1981; Broen et al., 1998; Knoflach, 1999). However, its status cannot be 

evaluated yet. 

> Eperigone eschatologica (Crosby) was first recorded in Europe from Germany and 

Belgium ( see Klein et al., 1995; Bosmans and Vanuytven, 1998) but very recently it 

was found in Switzerland in a private flat, most probably carried on a plant from a 

German garden centre (Hänggi, unpubl.). It remains to be seen whether it will become 

established in greenhouses in Switzerland. 

> Heteropoda venatoria (L.), a member of the family Thomisidae (crab spiders) of 

South-east Asian origin, was repeatedly reported from heated buildings, e.g. in zoos 

(Jäger, 2000). Surveys and research on the spider faunas of heated buildings and 

greenhouses would be a useful exercise, since this species is also able to penetrate 

human skin (c.f. Zoropsis spinimana). 

> Thanatus vulgaris Simon, a Mediterranean sister species of the native T. atratus 

Simon, would most probably be found in Swiss greenhouses if an intensive survey 

were undertaken (see Jones, 1997; Jäger, 2002).


5.6 «Banana spiders» and terrarium species 

Since the species introduced by trade in bananas and other tropical fruits (see e.g. 

Schmidt, 1971) cannot establish populations in our climate, they are only of medical 

interest, because they include some dangerous members of the family Ctenidae from 

South America. Pesticides used before or during transport will often lead to the death 

of spiders en route or shortly afterwards (pers. obs. by T. Blick of a ctenid which 

arrived in Bayreuth, Germany in a consignment of bananas from Brazil). 

However, some of the many stable populations of spider species in greenhouses are 

probably the result of such introductions with trade. Thus, it is possible that poisonous 

species, especially small ones, including some dangerous for humans could be accidentally 

introduced and established in greenhouses (see, e.g., Huhta, 1972). 

Spiders appropriately kept in terrariums are of no concern, but escaped specimens 

should be handled with care, since the bite of some species (although not many) can be 

dangerous for humans. If they escape into the wild they will die when temperatures 

drop, since all species are of tropical or subtropical origin. 

5.7 Discussion and recommendations 

Monitoring spider species currently expanding their range after introduction, and 

surveys at places prone to introductions, are recommended as elements of an early 

warning system. This would allow the spread of the alien species to be followed and 

document any displacement of native species. Some species are invading, but there is 

no way of evaluating their potential threat to native biodiversity. The data collected on 

synanthropic spiders in Switzerland, as well as other Central European countries, are 

too limited to allow any conclusions to be drawn. Some cases of established tropical 

species and increasing trade indicate the possibility of venomous spider species arriving 

in Switzerland. If a venomous spider becomes established, the public would need to 

be well-informed about how to handle the situation and anti-venom kits should be 

made available. 

Furthermore, to document threats to native species in natural habitats, the establishment 

of long-term surveys in specific habitats is recommended. Without further studies 

on alien spider species, potential impacts are only guesswork. 

Surveys for synanthropic alien spiders and their relatives are of lesser importance, as 

long as no dangerous spiders are introduced and the species that do arrive cannot 

become established outside. Thus, the costs of conducting surveys for these would 

probably not be justified. However, monitoring of some selected species (e.g. Oecobius 

maculatus Simon and Zoropsis spinimana) to document their spread would be both 

worthwhile and manageable.


In particular, we recommend an assessment of alien spiders in greenhouses and other 

heated buildings. Greenhouses in nurseries and garden centres are the most likely to be 

colonized by alien spider species, and from there these can be spread to households on 

plant material (e.g. Eperigone eschatologica). Research and monitoring are needed, 

because of the potential economic impact of some species. The first encounter with 

Uloborus plumipes is an example: a nursery started an inquiry to find out what species 

had infested their property after this spider had covered all plants with webs, so that 

plants became difficult to sell. Moreover, the possibility of accidental introductions of 

poisonous spiders should not be underrated. Nurseries would be the main targets for 

these monitoring programmes, but other heated buildings in botanical gardens and zoos 

should be included. 

The following are considered to have the greatest potential for economic impacts: 

> Mass outbreaks of nuisance species (see Ostearius melanopygius), but without 

causing real damage. 

> A dramatic increase in the population of the wall-inhabiting spider Dictyna civica. 

> The potential medical costs for treatments of bites of introduced poisonous spiders, 

see ‘banana spiders’, and escaped terrarium species. 

Having noted the potential threats to humans, it has to be stressed that broad use of 

pesticides against spiders is not a reasonable reaction, because of the non-target effects 

of these chemicals and the fact that publicity of such measures will exaggerate arachnophobia, 

already well-grounded in the human population. 

In conclusion, only a very small number of spiders and their relatives are considered as 

problem species on a global scale, including Central Europe (e.g. Welch et al., 2001 do 

not list any alien spiders for Scotland). A reasonable explanation could be that many 

phytophagous insects live in closer association with their host plants, e.g. eggs, larvae 

and pupae are firmly attached to host plants or inside them. This would facilitate their 

transport with plant material. Another factor is that spiders with their predatory behaviour 

are less obvious than phytophagous insects that damage their host plants. Moreover, 

as pointed out earlier, the group is rather neglected and many information gaps 

still exist. However, after successful introduction into a new area, many spiders are 

highly capable of a rapid expansion in range either by natural means such as ballooning 

or by hitching a ride on vehicles.


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6 > Molluscs – Mollusca 113 

6 > Molluscs – Mollusca 


The molluscs are a very large successful group of about 130,000 described species, 

making them second in number of species only to the arthropods (Remane et al., 1981). 

However, of the molluscs’ seven classes only two occur in Switzerland, since the 

others are strictly marine species. 

In the text below, gastropod and bivalve species are discussed separately. For ease of 

reference, in Table 6.2 the species are divided into terrestrial snails (including slugs), 

freshwater snails and bivalves, while the Fact Sheets are in alphabetical order of species. 

A total of 16 gastropods and three bivalves are regarded as established alien species. 

6.1 Snails and slugs (Gastropoda) 

Gastropods make up 70 % of all molluscs and are well represented in marine, freshwater 

and terrestrial habitats. About 196 terrestrial and 50 aquatic species occur in Switzerland 

(Turner et al., 1998). 

The exact natural distribution of the gastropod species in Switzerland is not well 

known, and many current populations may be early relocations (introductions within 

Switzerland). Snails are very successful at hitching a ride, so that many former barriers 

have been easily bridged through human-mediated transport. Snails arrived on plant 

material as early as during Roman times. The aquatic snail Viviparus ater (Molina) is 

an example of relocation in Switzerland. Its native range is believed to be south of the 

Alps, including the Ticino, but today its range north of the Alps encompasses the lower 

regions between Lac de Genève and Bodensee. It was released into Lac de Genève 

before 1900. 

Snails found in greenhouses are not covered by this report if they do not occur outside 

as well. Turner et al. (1998) provide a discussion of greenhouse snails and species that 

have been recorded only temporarily, and which are therefore not considered to be 

established in the wild. 

The snail Solatopupa similis (Bruguière) (Chondrinidae) was introduced to a location 

close to Locarno in the 19 th century for unknown reasons. This population thrives, but 

the species’ impact is considered minimal because of its very localized distribution.


The family Milacidae with two native species, has been supplemented in Switzerland 

with two more, i.e. Milax gagates (Draparnaud) and Tandonia budapestensis (Hazay), 

both from other parts of Europe. M. gagates has been found only in gardens, where it 

probably arrived with plant material, so it is not known whether it is established in 

Switzerland. T. budapestensis is an anthropochorous (disperses as a result of human 

activity) species that is widely distributed within Europe. It is regarded as a pest, 

especially in winter crops (Fischer and Reischütz, 1998), but is rather difficult to 

observe because of its cryptic, nocturnal habits. 

Another synanthropic species (in addition to members of the Milacidae) is Limacus 

flavus (L.) (Limacidae), which is only rarely encountered in Switzerland. It is likely 

that this species will be introduced with plant material in the future, but it is probably 

not adapted to the Swiss environment, so that it is less likely to become established. 

The slugs Deroceras sturanyi (Simroth) and D. panormitanum (Lessona & Pollonera) 

belong to the Agriolimacidae. This family is taxonomically challenging and new 

species have recently been described (Kerney et al., 1983). These slugs prefer fresh 

green plant material and therefore some are recognized as pests. The former species has 

been considered a pest in gardens, while the latter species is only rarely found in 

Switzerland. However, D. panormitanum is expanding its range in Europe and is 

increasingly reported as damaging plants of economic importance. This is a species 

that should be monitored, since it is likely to establish populations in agricultural areas, 

with the potential to cause economic damage in the near future. 

The origin of the slug Boettgerilla pallens Simroth (Boettgerillidae) is assumed to be 

the Caucasus, although Jungbluth (1996) argued that it might be a native species in 

Central Europe which had not been reported earlier. Most collections of slugs are fairly 

recent and the lack of a shell makes it difficult to find species as subfossils. This species 

is a predator of slug eggs and young slugs (Reischütz, 2002), so it is a beneficial 

organism in agricultural settings rather than a pest, as sometimes stated. However, in 

natural localities, it may have a negative impact on native slugs through predation. 

Arion lusitanicus Mabille (Arionidae) (see Fact Sheet) is rapidly expanding its range, 

and is the most serious invader amongst the snails and slugs. It is not only a pest in 

agriculture and gardens, but also displaces a native congeneric species in the lowland 

parts of Switzerland (Turner et al., 1998). 

The snail Hygromia cinctella (Draparnaud) (Hygromiidae) has been accidentally 

introduced into the northern parts of Switzerland, but could be native around Genève or 

in the Ticino. It was introduced prior to the start of malacological recording and is 

mostly found in gardens and other anthropogenic settings (Kerney et al., 1983). 

The only introduced species of Helicidae is Cryptomphalus aspersus (O.F. Müller), 

which was introduced prior to the start of malacological recording. It is mostly found in 

gardens and other anthropogenic habitats, although it is recorded from natural habitats, 

e.g. in the Valais. Its environmental impact is not known, but it is regarded as a pest in 

gardens.


The freshwater snail Potamopyrgus antipodarum (Gray) (Hydrobiidae) (see Fact 

Sheet) is one of the few long-distance invaders in this group. It is native to New Zealand 

and has been spread around the world probably with ballast water between freshwater 

systems and on ornamental aquatic plants. Haynes et al. (1985) have suggested 

another pathway as they have shown that P. antipodarum can survive a six-hour passage 

through the gut of a trout and produce live young shortly afterwards. It is very 

likely to induce ecosystem changes because of its enormous numbers in some places. 

Two Physella species, Physella acuta (Draparnaud) and P. heterostropha (Say) (Physidae), 

have been introduced into Switzerland. The latter species is of North American 

origin, but the origin of the former species is disputed, although it probably originates 

in south-western Europe. Since P. heterostropha is cold-tolerant, the expansion of its 

range could lead to competition with native snails. While Turner et al. (1998) state that 

the two species are morphologically distinct and occur together in some parts of Switzerland, 

Anderson (2003) records the two species as synonyms. 

Two alien species of Planorbidae, Gyraulus parvus (Say) and Planorbarius corneus 

(L.), probably cause no concern, because the former is a rare species of North American 

origin and the latter is a native species in Europe. It is likely that P. corneus cannot 

establish populations in Switzerland, because of unsuitable climatic conditions. However, 

it is found frequently, probably released from aquariums or transported by birds 

from garden ponds. 

6.2 Bivalves (Bivalvia) 

There are only three introduced and established bivalves, but they are of concern, 

because of their high abundance and feeding behaviour. 

The two Corbicula species (Corbicula fluminea (O.F. Müller) and C. fluminalis (O.F. 

Müller)) are very similar, so that they are discussed together (see Fact Sheet). Hakenkamp 

and Palmer (1999) have demonstrated the strong influence Corbicula spp. have on 

ecosystem functioning by linking pelagic and benthic processes as a result of their 

intense filter feeding activity. 

The zebra mussel Dreissena polymorpha (Pallas) (Dreissenidae) (see Fact Sheet) is 

one of the most widely cited case studies of a freshwater invader. Whereas the species 

is often considered to be beneficial in Europe, especially as a food source for diving 

ducks, it is inflicting huge costs to the USA and Canada in the Great Lakes area. The 

transformation of freshwater ecosystems by D. polymorpha is documented by Strayer 

et al. (1999) and Karateyev et al. (2002). 

The 19 established alien mollusc species belong to very different groups, i.e. 14 families, 

with only one or two species per family. However, the species can be considered 

as belonging to a number of major groups. Seven species from four families of slugs 

(Milacidae, Limacidae, Agriolimacidae and Arionidae) have been introduced into


Switzerland. The total number of species in these families found in Switzerland is 33, 

so about 21 % are introduced. This is a rather high percentage, as will be seen below. It 

seems that slugs are very good at hiding in plant material, decaying material and other 

commodities and are widely transported. Today there are three established introduced 

bivalves, which is about 11 % of the total of 28 species found in Switzerland. Probably 

six out of the 50 freshwater snail species are alien (12 %). Finally, the large group of 

terrestrial snails (terrestrial molluscs excluding the four families of slugs mentioned 

above) comprise approximately 160 species, of which a mere three species (2 %) are 

introduced. With the exception of the slugs, the pattern that emerges might be a random 

phenomenon due to small sample sizes; whereby a few introductions of species in 

smaller groups form a higher percentage of the total fauna. The extreme would be a 

randomly introduced species from a group comprising one species, which would form 

100 % of the fauna of that particular group. The total percentage of established molluscs 

is about 6.9 % (19 of 274 species). 

A comparison of the established mollusc species in Switzerland and Austria shows a 

very similar picture; the percentage of introduced mollusc species is 6.9 % in Switzerland 

and 7.6 % in Austria (Essl and Rabitsch, 2002). Of course, the total number of 

species differs because Austria is about twice the size of Switzerland (83,855 km 2 

compared to 41,285 km 2 ). About 435 mollusc species occur in Austria, including 33 

aliens. Even more established alien mollusc species are recorded in Germany, about 40, 

but five of those are marine (Geiter et al., 2002). There is a remarkable overlap of the 

alien species in the three countries, emphasizing the regular introduction of some 

species (in some cases using the same frequent pathways). 

Most of the established alien mollusc species originate within Europe (Tab. 5.1), 

although the exact origin of some Ponto–Caspian species is not known, so whether 

these species originate in Europe or Asia may be disputable. Only five (about a quarter) 

of the species travelled a long distance to Switzerland. The majority have apparently 

profited from short-distance transport of commodities between European countries. 

Tab. 6.1 > Origin of alien molluscs established in Switzerland. 

Origin 

Europe 13 

Asia 2 

North America 2 

Switzerland 1 

New Zealand 1 

Total 19 

No. species


This leads to an evaluation of the pathways by which these 19 species arrived in Switzerland. 

It is possible that at least some species could have arrived by several pathways, 

and for some species the pathways by which they were introduced are speculative 

rather than proven. The most likely pathways for each species are listed in Table 

6.2. About 74 % (14 species) were accidentally introduced, while the others were 

released for unknown reasons and from aquariums (often with the good intention of 

‘freeing’ surplus animals). Five of the eight aquatic species were probably transported 

by boats and ships, either in ballast water or attached to hulls. The accidental terrestrial 

introductions were most likely made with imported vegetables and other plant material. 

The impacts of the established alien molluscs are discussed in some detail and further 

references are given in the Fact Sheets and in the text above. Only five out of 19 species 

can be regarded as harmless, based on present knowledge. The terrestrial slugs 

(and to a certain extent snails) are mainly economic pests of agriculture and in gardens. 

However, research on environmental impacts is largely lacking, with the exception of 

Arion lusitanicus displacing the native A. rufus (L.). The situation is different in freshwater 

ecosystems, with demonstrated dramatic impacts of the introduced bivalves on 

native biodiversity and ecosystem functioning. The introduced bivalves are a novel life 

form in their new range, because of their densities and intense filter-feeding activities, 

which alter the correlation between benthic and pelagic communities. They may also 

have some economic impact because of their colonization of pipes and other artificial 

structures. 

In general, alien species should be treated separately from the native fauna and should 

not appear on a Red List of endangered species, when they are beyond doubt introduced. 

This is especially true for the intercontinental invader, since some European 

species could also expand their range into Switzerland and distinguishing between the 

two categories (aliens of European and extra-continental origin) is often challenging. 

However, species such as Physella heterostropha, a Nearctic invader, should not 

appear on the Red List as potentially vulnerable (‘potentiell gefährdet’), as it does. 

Thus, the concept of the Red List of Switzerland should be re-addressed, with alien 

species being excluded. 

Prevention of new mollusc invasions is dependent on identification of the pathways of 

introduction. Plant health inspection has improved recently and should be vigilant for 

new arrivals of slugs and snails, as well as insects and other invertebrates. The ballast 

water issue is currently being addressed for sea-going ships by the International Maritime 

Organization (IMO) whereby methods are evolving to treat ballast water. Some of 

these measures can also be used for ships on inland waterways. Another crucial topic is 

public education and awareness; when using a boat, boots or fishing gear, people 

should take care not to transport potential hitchhikers. Aquarium owners and pet store 

merchants need to be made aware of potential problems arising from the release of 

pets. 

Several slug species are major pests in crops, and management strategies to reduce 

harvest losses have been implemented. Slug pellets, a bait that contains slug attractants 

and a molluscicide (e.g. metaldehyde), are frequently used. Alternative methods in-


clude the use of nematodes and runner ducks (a special breed of the mallard) as biological 

control agents, as well as hand-picking. The latter approach, although very 

laborious, was successfully used to eradicate the giant African snail (Achatina fulica 

Bowdich) in Florida, USA (Simberloff, 1996). This was a remarkable achievement. 

Slug fences and beer traps are often used in gardens. However, these methods are 

usually used to protect plants at a specific location and are not designed to reduce 

numbers of snails and slugs of environmental concern on a large scale. 

In conclusion, the freshwater ecosystems need to receive more attention and the potential 

impacts of alien invaders should not be underrated. It is generally very difficult to 

give conclusive proof of the impacts of invasive species on native biodiversity. However, 

many of the freshwater invaders reach remarkable densities and will have impacts 

on natural ecosystems. These invaders are not only molluscs, but often crustaceans and 

fish (see respective chapters). The boom-and-bust phenomenon (Williamson, 1996) 

that is frequently observed with many invading species seems often to be caused in 

European freshwater systems by the arrival of yet another invader. Thus, this does not 

solve the problem, but simply shifts it to another invader and its impacts. In a terrestrial 

context, the slug Arion lusitanicus is probably of greatest concern in Switzerland (and 

Central Europe). 

Tab. 6.2 > Established alien molluscs in Switzerland. 

Scientific name Family Year Origin Pathway Impact Note 

Terrestrial snails 

Solatopupa similis Chondrinidae 19th Genoa, Italy Released to enrich Probably harmless Only one location near Lo- 

(Bruguière) century fauna carno, Ticino 

Milax gagates (Drapar- Milacidae 1968 Western and Accidental with vegeta- Pest in crops and gardens Not clear whether established 

naud) southern 

Europe 

bles shipment? or only repeatedly introduced 

Tandonia budapesten- Milacidae 1935 South-eastern Accidental with vegeta- Pest, in particular in winter crops, Anthropochorous – introduced 

sis (Hazay) Europe bles shipment? when abundant widely by human-mediated 

transport 

Limacus flavus (L.) Limacidae 1927 Mediterranean Accidental Harmless Very rare in Switzerland, mostly 

synanthropic 

Deroceras sturanyi Agriolimacidae 1963 South-eastern Accidental Damage to plants in gardens Mostly secondary habitats 

(Simroth) Europe 

Deroceras panormita- Agriolimacidae 1982 South-western Accidental Future damage anticipated Very rare in Switzerland, only in 

num (Lessona & 

Pollonera) 

Europe gardens and parks 

Boettgerilla pallens Boetgerillidae 1960 Caucasus? Accidental Predator of native slugs? Impact not known, but a 

Simroth predator of slugs 

Arion lusitanicus Mabille Arionidae 1950s Western Accidental Most serious pest in gardens and Most problematic terrestrial 

Europe agriculture 

Displaces native Arion rufus (L.) 

snail


Scientific name 

Hygromia cinctella 

(Draparnaud) 

Cryptomphalus asperus 

(O.F. Müller) 

Freshwater snails 

Family Year Origin Pathway Impact Note 

Hygromiidae 1824? Mediterranean Accidental Harmless Perhaps native in southern and 

south-western Switzerland, but 

introduced to the northern parts 

Helicidae Before 

1789 

Viviparus ater (Molina) Viviparidae Before 

1900 

Potamopyrgus 

antipodarum (Gray) 

Physella acuta 

(Draparnaud) 

Physella heterostropha 

(Say) 

South-western 

Europe 

South Switzerland 

Released Garden pest Mainly synanthropic, but also 

found in natural habitats 

Accidental introduction 

with boat traffic 

Hydrobiidae 1972 New Zealand Accidental introduction 

with boat traffic and 

birds 

Physidae 1848 South-western 

Europe 

Physidae Before 

1991 

Accidental release from 

aquariums? 

Gyraulus parvus (Say) Planorbidae 1994 North America Accidental with aquatic 

plants 

Planorbarius corneus 

(L.) 

Bivalves 

Corbicula fluminalis 


Corbicula fluminea 


Probably harmless Native in southern Switzerland 

Can drastically alter primary 

production 

Rapid expansion throughout 

Europe 

Not known Maybe of North American origin 

North America Accidental Competition with native snails? Expanding in Europe 

Not known Rare in Switzerland 

Planorbidae 1840 Europe Releases from aquariums 

Probably harmless Perhaps not established 

Corbiculidae 1997 Asia, introduced 

via 

North America 

Corbiculidae 1997 Asia, introduced 

via 

North America 

Probably ballast water Competition with native bivalves The two Corbicula species are 

very similar 

Probably ballast water Competition with native bivalves The two Corbicula species are 

very similar 

Dreissena polymorpha Dreissenidae 1850 Ponto– Probably ballast water Ecosystem engineer. Species of high concern 

(Pallas) Caspian and/or hull fouling Overgrows native mussel species 

region .Costs to prevent them clogging 

pipes, etc. are fairly small 

compared with North America


References 

Anderson, R. (2003) Physella (Costatella) acuta Draparnaud in Britain and 

Ireland – its taxonomy, origins and relationships to other introduced 

Physidae. Journal of Conchology 38, 7–21. 



Fischer, W. and P.L. Reischütz (1998) General aspects about the 

slugpests. Die Bodenkultur 49 (4), 281–292. 



Hakenkamp, C.C. and M.A. Palmer (1999) Introduced bivalves in 

freshwater ecosystems: the impact of Corbicula on organic matter 

dynamics in a sandy stream. Oecologia 119, 445–451. 

Haynes, A., Taylor, B. J. R. and M.E. Varley (1985) The influence of the 

mobility of Potamopyrgus jenkinsi (Smith, E.A.) (Prosobranchia: 

Hydrobiidae) on its spread. Arch. Hydrobiol. 103, 497–508. 

Jungbluth, J.H. (1996) Einwanderer in der Molluskenfauna von 

Deutschland. I. Der chorologische Befund. In: Gebhardt, H., Kinzelbach, R. 

and S. Schmidt-Fischer (eds) Gebietsfremde Tierarten. Auswirkungen auf 

einheimische Arten, Lebensgemeinschaften und Biotope; 

Situationsanalyse. Ecomed Verlagsgesellschaft, Landsberg, pp. 287–296. 

Karateyev, A.Y., Burlakova, L.E. and D.K. Padilla (2002) Impacts of zebra 

mussels on aquatic communities and their role as ecosystem engineers. 

In: Leppäkoski, E., Gollasch, S. and Olenin, S. (eds) Invasive aquatic 

species of Europe. Distribution, impacts and management. Kluwer 

Academic Publishers, Dordrecht, Netherlands, pp. 426–432. 

Kerney, M.P., Cameron, R.A.D. and J.H. Jungbluth (1983) Die 

Landschnecken Nord- und Mitteleuropas. Paul Parey, Hamburg and 

Berlin, Germany, 384 pp. 

Reischütz, P. (2002) Weichtiere (Mollusca). In: Essl, F. and W. Rabitsch 

(eds) Neobiota in Österreich. Umweltbundesamt, Wien, Austria, pp. 214– 

221. 

Remane, A., Storch, V. and U. Welsch (1981) Kurzes Lehrbuch der 

Zoologie. Gustav Fischer Verlag, Stuttgart, 537 pp. 

Simberloff, D. (1996) Impacts of introduced species in the United States. 

Consequences 2 (2), 13–23. 

Strayer, D.L., Caraco, N.F., Cole, J.J., Findlay, S. and M.L. Pace (1999) 

Transformation of freshwater ecosystems by bivalves: A case study of 

zebra mussels in the Hudson River. Bioscience 49, 19–27. 

Turner, H., Kuiper, J.G.J., Thew, N., Bernasconi, R., Rüetschi, J., 

Wüthrich, M. and M. Gosteli (1998) Mollusca, Atlas. Fauna Helvetica. 

CSCF, Neuchâtel, 527 pp. 

Williamson, M (1996) Biological invasions. Chapman & Hall, London, 

Weinheim, New York, Tokyo, Melbourne, Madras, 244 pp.

7 > Other selected invertebrate groups 121 

7 > Other selected invertebrate groups 

Prepared by Rüdiger Wittenberg and Marc Kenis 

This chapter gives only a few examples of alien species from groups which can cause 

problems for the environment not dealt with in other chapters of this report. It is not 

possible to give comprehensive lists of most of these invertebrate groups. Therefore, 

the objective is to give a brief overview of potential problematic species for biodiversity 

and ecosystems in Switzerland. As mentioned before, there is a great need for 

more taxonomic work on these groups, not only the alien species, but the native species 

as well. Based on future work, more comprehensive lists of some groups may be added 

in the future to complete the knowledge of established alien species in Switzerland. 

7.1 Nematodes – Nemathelminthes 

Nematodes are a large but little-known group of tiny worms. There is no comprehensive 

checklist of species in this group for Switzerland, but many species are of great 

economic importance as pests in agriculture and forestry. Species exclusively causing 

economic damage are not part of the report, since they are the best-known species in 

this group; the Swiss Federal Research Stations are actively working on them, and 

there are other sources dealing with them, e.g. CABI (2001) lists the following 11 

problematic nematodes for Switzerland: Globodera pallida (Stone) Behrens, G. rostochiensis 

(Wollenweber) Behrens, Heterodera avenae Wollenweber, H. schachtii 

A.Schmidt, Longidorus elongatus (de Man) Micoletzky, Meloidogyne arenaria (neal) 

Chitwood, M. hapla Chitwood, Pratylenchus penetrans (Cobb) Filipjev & Schuurmans, 

Punctodera punctata (Thorne) Mulvey & Stone, Xiphinema diversicaudatum 

(Micoletzky) Thorne, and X. index Thorne & Allen. 

The pine wood nematode (Bursaphelenchus xylophilus (Steiner & Buhrer) Nickle) 

(see Fact Sheet) is an example of a species that has recently been found in Europe and 

is considered to be a potential threat to Pinus spp. here. Thus, its wider spread within 

Europe should be prevented. 

The nematode Anguillicola crassus Kuwahara, Niimi & Itagaki (Anguillicolidae) is an 

example of a nematode that is having an extensive impact by attacking a fish species. 

This nematode is a parasite of eel species. In Europe the native Anguilla anguilla L. is 

under threat following the invasion of the nematode. The nematode was accidentally 

introduced with imports of live Asian eels to Europe in 1982 (Konecny et al., 2002). 

Besides the negative impact on natural populations of the European eel, it affects 

Europe’s important fishing industries. The European eel is native in the river systems


emptying into the Atlantic, as its life history involves spawning grounds in the Sargasso 

Sea. It has itself been introduced to some parts of Europe, e.g. the Danube basin. 

The construction of the Rhine–Danube Canal opened the way from the Rhine, where it 

is native, to the Danube basin. 

Another nematode was accidentally introduced into Europe together with its North 

American host, i.e. Baylisascaris procyonis (Stefanski & Zarnowski) with the raccoon, 

Procyon lotor (L.) (see mammal chapter). This species is of concern for human health. 

7.2 Flatworms – Turbellaria, Plathelminthes 

In the group Turbellaria (part of the Plathelminthes), one species is an abundant alien 

inhabitant of lakes and rivers, including the Rhine in Switzerland. The predatory 

aquatic flatworm Dugesia tigrina (Gerard) is abundant and widespread in standing and 

slow-moving water bodies in Europe (Pöckl and Rabitsch, 2002). It was probably 

introduced on aquarium plants or fish from North America around 1900. Although this 

species is found in high densities, a negative impact has not (yet) been shown. 

Other flatworms of environmental concern are terrestrial. The New Zealand flatworm 

(Artioposthia triangulate (Dendy)) (see Fact Sheet) serves as an example of several 

predatory flatworm species introduced into Europe from New Zealand and Australia. 

Native earthworms are a major prey for these flatworms. Earthworms play an important 

role in nutrient cycling in soil, so that their reduction could lead to ecosystem 

changes. They are also a significant element of vertebrate prey. 

7.3 Segmented worms – Annelida 

The Ponto–Caspian invaders in European waters are an interesting group – see the 

Crustacea Chapter for more information. The annelid polychaete worm Hypania 

invalida (Grube) has become very numerous in the sandy sediment of the Rhine, where 

it burrows its tubes vertically into the mud (Rey and Ortlepp, 2002; Van der Velde et 

al., 2002). The impact of this abundant species has not been evaluated. It is approximately 

1–2 cm long and can reach densities of about 10,000 individuals per square 

metre. The species reached the Rhine after the opening of the Rhine–Danube canal, 

probably in the ballast tanks of ships. 

Another possibly harmless species in the group Annelida, but an oligochaete worm 

(Tubificidae), is the large (up to 20 cm long) Branchiura sowerbyi Beddard, which 

originates in south-eastern Asia. It was probably introduced on tropical aquatic plants 

at the beginning of the 20 th century. At first it occurred only in greenhouses, but it 

adapted to the colder climate and is now found in many slow-moving rivers (Pöckl and 

Rabitsch, 2002). It lives in self-made tubes in muddy soil and feeds on detritus.

7 > Other selected invertebrate groups 123 

A member of a third group of the Annelida is the leech Caspiobdella fadejewi (Epshtein) 

(Hirundinea; Piscicolidae), which can be found in low densities in the Rhine 

between Basel and the Bodensee. This species, also from the Ponto–Caspian system, is 

an ectoparasite of various fish species. 

7.4 Centipedes and millipedes – Myriapoda 

A neglected group in this report is the Myriapoda, including the Diplopoda and the 

Chilopoda. It is impossible to give a comprehensive list. In particular the former group, 

as plant and detritus feeders, are probably regularly introduced with plant and soil 

material. Some tropical or subtropical species might be restricted to greenhouses. 

However, the number of established species in the wild is likely to be small (probably 

less than ten species) and none is of particular threat to native biodiversity and ecosystems. 

References 


Wallingford, UK. 

Konecny, R., Schabussova, I. and H. Sattmann (2002) ”Helminthen“ – 

Neozoen der Fische Österreichs. In: Essl, F. and W. Rabitsch (eds) 

Neobiota in Österreich. Umweltbundesamt, Wien, pp. 221–224. 

Pöckl, M. and W. Rabitsch (2002) Ausgewählte aquatische Neozoen 

(Cnidaria, Plathelminthes, Kamptozoa, Annelida, Isopoda). In: Essl, F. and 

W. Rabitsch (eds) Neobiota in Österreich. Umweltbundesamt, Wien, pp. 

228–239. 

Rey, P. and J. Ortlepp (2002) Koordinierte biologische Untersuchungen 

am Hochrhein 2000; Makroinvertebraten. BUWAL Schriftenreihe Umwelt 

Nr. 345, Gewässerschutz, 98 pp. 

Van der Velde, G., Nagelkerken, I., Rajapogal, S. and A. Bij de Vaate 

(2002) Invasions by alien species in inland freshwater bodies in Western 

Europe: the Rhine delta. In: Leppäkoski, E., Gollasch, S. and Olenin, S. 

(eds) Invasive aquatic species of Europe. Distribution, impacts and 

management. Kluwer Academic Publishers, Dordrecht, pp. 426–432. 

Weidema, I.R. (ed) (2000) Introduced species in the Nordic countries. 

Nordic Council of Ministers, Copenhagen, 242 pp. 




pp.


8 > Lichens (Lichen-forming fungi) 


There are no lichens known to be introduced and established in Switzerland 

(C. Scheidegger, pers. comm.). Lichens, with their extremely slow growth, seem illadapted 

to human-mediated transport and the colonization of new regions. There is no 

doubt that species must be introduced with timber, etc., but the step from introduction 

to establishment has apparently not been achieved. Breuss (2002) mentions Anisomeridium 

polypori (Ellis & Everh.) M.E. Barr as a neomycete for Austria. However, 

recently described new species are not necessarily introduced. They could also have 

been overlooked in the past, in particular as floristic research in microlichens does not 

have a long history and is rather incomplete. Changes in the environment can also 

favour some previously rare species, so that they become more abundant and widespread, 

feigning a new arrival. Aptroot (1999) doubts the neomycete character of A. 

polypori, instead assuming a wide natural distribution. 

References 

Aptroot, A. (1999) Notes on taxonomy, distribution and ecology of 

Anisomeridium polypori. Lichenologist 31 (6), 641–642. 

Breuss, O. (2002) Flechten. In: Essl, F. and W. Rabitsch (eds) Neobiota in 

Österreich. Umweltbundesamt, Wien, pp. 214–221.

9 > Fungi and a selected bacterium 125 

9 > Fungi and a selected bacterium 

Prepared by Rüdiger Wittenberg and Marc Kenis 

Fungi are an often-neglected group and it is not possible to compile a list of neomycetes 

for Switzerland, let alone to list the fungi occurring in Switzerland. It is a group 

where the percentage of undescribed species is exceptionally high. In this report, 

species which are of concern for native biodiversity and economics alike are summarized. 

Species exclusively causing economic damage are not part of the report, since 

they are the best-known species; the Swiss Federal Research Stations are responsible 

for working on them, and there are also other sources, such as university research 

departments, dealing with them. Two examples of excellent sources are: 

> The Alert List of the European and Mediterranean Plant Protection Organization 

(EPPO). The purpose of the Alert List is to draw attention to certain pests that may 

present a risk to member countries, thereby functioning as an early warning system: 

http://www.eppo.org/QUARANTINE/Alert_List/alert_list.html 

> The Crop Protection Compendium (CPC) (see e.g. CABI, 2004) lists, for example, 

104 fungi for Switzerland and provides Fact Sheets incorporating exhaustive information 

on the species. It is also available on the Internet at: 

http://www.cabi.org/compendia/cpc/index.htm 

These sources give other links as well, so that a wealth of information is available for 

the species of economic importance. 

Six fungal species of immediate threat to the native biodiversity are discussed in this 

section. There is also one bacterium, which is pathogenic to plants, included in the text 

and a Fact Sheet. 

Chestnut blight (Cryphonectria parasitica (Murrill) Barr) (see Fact Sheet) was introduced 

into North America and Europe. In North America chestnut blight has been an 

ecological disaster. It changed the tree composition of the eastern forests completely by 

removing one of the dominant trees, Castanea dentata (Marshall). Fortunately, it 

seems that the European congeneric is less susceptible to the disease, although it has 

suffered and tree composition is altering, in particular in the Ticino. 

Another tree-attacking fungus, causing tremendous ecosystem changes in Europe, is 

Dutch elm disease (Ceratocystis ulmi (Buisman) C.Moreau and C. novo-ulmi (Brassier)) 

(see Fact Sheet). Mature elm (Ulmus spp.) trees have disappeared from the landscape 

in many regions. C. novo-ulmi seems to have arrived decades after C. ulmi and is 

replacing it in many parts of Europe, e.g. Austria (Kirisits et al., 2001). Reinhardt et al.


(2003) estimate that Germany incurs annual costs of about €5 million for the removal 

and replacement of trees, the lost value of dead trees, and additional expenditure of 

planting resistant varieties. 

While Phytophthora quercina Jung et al. (see Fact Sheet) is a rather recent invader (or 

at least attention has been drawn to it by its recent impact), P. ramorum Werres, de 

Cock & Man in’t Veld (sudden oak death) (see Fact Sheet) is already well-known 

from its devastating effect in North America. In Europe it is still only a problem in 

nurseries, but it can be expected to infest native forests in the not-too-distant future. 

Many woody hosts have been shown to be susceptible to sudden oak death and it has 

been recorded from Switzerland (Heiniger and Stadler, 2003). 

The crayfish plague (Aphanomyces astaci (Schikora)) (see Fact Sheet) is one of the 

most devastating fungi attacking European wildlife. The fungus was introduced with 

North American crayfish species, which are asymptomatic carriers of the disease, into 

Europe. The European crayfish species are highly susceptible and almost 100 % die 

within two weeks of infection. There are regular outbreaks in European populations 

resulting in total collapse (Voglmayr and Krisai-Greilhuber, 2002). 

The bacterium Erwinia amylovora (Burrill) Winslow et al. (see Fact Sheet) is the 

causal agent of fire blight, which was first found on Cotoneaster species and is now 

widely distributed in Switzerland (Hasler et al., 2002). 

An interesting case of a mutual relationship between two invaders may be the association 

between mycorrhizal fungi and plant species. There is some evidence that alien 

mycorrhiza can help their alien host plant to become a weed in the introduced range 

(e.g. Crawley, 1993; Harrington et al., 1998). In that way, an introduced mycorrhiza 

might have an indirect detrimental effect on native biodiversity. 

In can be concluded that although quarantine measures are successfully implemented in 

Switzerland, non-crop plants need to get more attention, e.g. plants in the nursery 

industry. The few examples described here indicate the enormous impacts diseases can 

have. Some introduced diseases are completely changing entire ecosystems by eliminating 

important key species. Moreover, there are human diseases not mentioned in 

this report with global impact, such as AIDS (a viral disease). 

The Fact Sheets are presented after the references, in alphabetical order for ease of 

location of specific sheets.

9 > Fungi and a selected bacterium 127 

References 


Wallingford, UK. 

Crawley, M.J. (1993) Succeeding in the sand dunes. Nature 362, 17–18. 

Harrington, K.C., Hodder, L.M. and H.A. Outred (1998) Biology and control 

of pypgrass. Proceedings, 51 st New Zealand Plant Protection Conference, 

pp. 255–259. 

Hasler, T., Schaerer, H.J., Holliger, E., Vogelsanger, J., Vignutelli, A. and 

B. Schoch (2002) Fire blight situation in Switzerland. Acta Horticulturae 

590, 73–79. 

Heiniger, U. and Stadler, B. (2003) Gefährliche Quarantänekrankheit 

gefunden. Phytophthora ramorum jetzt erstmals auch in der Schweiz. Der 

Gartenbau 51/52/2003, pp. 10–12. 

Kirisits, T., Krumböck, S. Konrad, H., Pennerstorfer, J. and E. 

Halmschlager (2001) Untersuchungen über das Auftreten der Erreger der 

Holländischen Ulmenwelke in Österreich. Forstwissenschaftliches 

Zentralblatt 120, 231–241. 




Voglmayr, H. and I. Krisai-Greilhuber (2002) Pilze. In: Essl, F. and W. 

Rabitsch (eds) Neobiota in Österreich. Umweltbundesamt, Wien, pp. 214– 

221.


10 > Plants – Planta 

Prepared by André Gassmann and Ewald Weber 

10.1 Introduction and terminology 

The expansion of alien plants within Central Europe began with the introduction of 

agriculture about 7,000 years ago and the subsequent spread of weeds. In Europe, as in 

most regions of the world, the number of alien plant species has increased considerably 

in the past 200 years as a result of increasing trade, tourism and disturbance. The 

increasing number of naturalized alien plant species with negative impacts on plant 

communities is viewed as a major component of global change. Successful invaders 

can affect the invaded communities in various ways, e.g. reducing the local diversity, 

driving rare native species to extinction (e.g. by competition or hybridization), changing 

habitat structures and ecosystem functioning, or increasing erosion. Plants are 

particularly notorious invaders, since they are capable of changing the food web at the 

base, which can ripple through the entire ecosystem. In Switzerland, with the exception 

of the Alps, wildlife and areas of conservation value are usually restricted to small 

areas, surrounded by heavily disturbed habitats or urban areas. In such small areas, 

invasive plant species pose additional threats to the native plant and animal diversity. 

Moreover, new plant invaders in Switzerland and in Europe can also affect human 

health (e.g. Ambrosia artemisiifolia L. and Heracleum mantegazzianum Sommier et 

Levier) or are a potential threat to the agro-economy (e.g. Senecio inaequidens DC.). 

This report gives an overview of alien and invasive plant species with regard to the 

Swiss flora. Some of the ecological and biological characteristics of alien plants in 

Switzerland are discussed and a list of plant invaders or potential invaders is provided. 

In this context, it is important to note that different original sources may cite different 

numbers of alien plant species. For example, Moser et al. (2002) list 350 neophytes. A 

number of these species are given a different status in Lauber and Wagner (1998). In 

addition, the species lists are not identical. For example, Moser et al. (2002) list two 

ferns as neophytes (Cyrtomium falcatum K. Presl, C. fortunei J. Sm.) which are not 

included in Lauber and Wagner (1998). The same holds for Crataegus lindmanii 

Hrabetova and C. rhipidophylla Gand. In contrast, species like Cotoneaster bullata 

Bois, C. dammeri Schneider, Helianthus rigidus (Cassini) and Paspalum dilatatum 

Poiret are not included in Moser et al. (2002). Excluding cultivated species that occur 

rarely as subspontaneous species (‘C’ plants in Moser et al. (2002)), we found in total 

over 70 alien species which are included in either one of the two lists but not in the 

other. Most of the variation originates from whether cultivated species are considered 

to be subspontaneous or not. In addition, another 60 species of European origin are 

controversial with regard to their alien status in Switzerland. Thus, different authors

10 > Plants – Planta 129 

have different approaches to the treatment of species, and there is no ultimately correct 

source. However, either source can be used to seek general patterns in geographic 

origins, life form distribution, or the numbers of neophytes present. Because Moser et 

al. (2002) do not provide standardized information on plant status and plant origin, we 

used the information provided by Lauber and Wagner (1998) to seek these general 

patterns. 

There is much variation in the definition of some of the terms presented below. In 

particular, there is controversy about the definition of ‘invasive species’ in the literature. 

The term ‘invasive species’ often refers exclusively to species penetrating into 

natural and semi-natural habitats although it is often difficult to clearly separate seminatural 

from human-made habitats. The terms ‘weeds’ and ‘weedy species’ are consequently 

devoted to plants causing problems in managed areas. Some authors call any 

alien plant species that spreads spontaneously in the introduced range an invasive 

species, irrespective of whether the species has harmful effects or not. For practical 

reasons, such a broad definition is not useful. 

In this chapter, the term ‘invasive species’ always refers to plants of alien origin, while 

the term ‘weed’ implies an indigenous species. Alien species may become invasive 

primarily in human-made habitats or agricultural land and thus have economic rather 

than ecological effects (e.g. Ambrosia artemisiifolia and Cyperus esculentus L.). It 

must be stressed however that most invasive plants are of greater concern in natural or 

semi-natural areas. It should be pointed out also that the spread of many naturalized 

species is primarily in highly disturbed areas of low ecological (or economic) value but 

this situation may change for many plant species in the future. In contrast, native 

species can pose problems by becoming abundant in conservation areas influenced by 

human activities, e.g. Phragmites australis (Cavanilles) or Rubus spp. This report does 

not consider native species that are weeds in agricultural land or may be of concern in 

natural or semi-natural areas. 

The terminology presented below has been adapted from Richardson et al. (2000) and 

Weber (1999a). 

> Alien (non-native, non-indigenous, introduced) plants: plant taxa (species, subspecies 

or lower taxon) in a given area whose presence there is due to intentional or 

accidental introduction as a result of human activity. Unless specified, cultivated 

plants that have not escaped from cultivation are not treated as alien species. 

> Native (indigenous) plants: plant taxa occurring within their natural range and 

dispersal potential (i.e. within the range they occupy naturally or could occupy without 

direct or indirect introduction or care by humans). 

> Neophyte plants (or neophytes): alien plants introduced during modern times (after 

1500 A.D.) and which have become naturalized. Archeophyte plants (or archeophytes) 

are those that were introduced before 1500 A.D. This report does not treat 

the two groups separately. 

> Casual (transient, ephemeral) plants: alien plants that may flourish and even 

reproduce occasionally in an area, but which do not form self-replacing populations, 

and which rely on repeated introductions or habitat disturbance for their persistence.


> Adventive plants: casual alien plants that have been accidentally introduced as a 

result of human activity. 

> Subspontaneous plants: casual alien plants escaped from cultures. 

> Naturalized plants: Alien plants that reproduce consistently and sustain populations 

over many life cycles without direct intervention by humans, (or in spite of human 

intervention); they often recruit offspring freely, usually close to adult plants, and do 

not necessarily invade their habitat. 

> Invasive plants (plant invaders): Naturalized plants that produce reproductive 

offspring, often in very large numbers, at considerable distances from parent plants, 

and thus have the potential to spread over a considerable area. Invasive plants can 

affect the invaded natural or semi-natural communities in various ways. Invasive 

plants can also affect human-made habitats and have direct economic effects. The 

term environmental weeds is sometimes used for those invasive plants having an 

impact in natural areas and semi-natural areas; and the term alien weeds is sometimes 

used for those alien plants that are weedy in managed habitats, such as agriculture. 

> Weeds: native plants that grow in sites where they are not wanted and which have 

detectable economic or environmental effects. 

10.2 The native and alien flora of Switzerland 

The list of alien species present in Switzerland (Table 10.6) includes both archaeophytes 

and neophytes. However, in this list, the neophytes of Flora Helvetica (Lauber 

and Wagner, 1998) are marked as such. A few species that have become naturalized 

recently (e.g. Ludwigia grandiflora (Michaux) and Lysichiton americanus Hultén & St. 

John) have been added to the alien species amongst the 3000 plant taxa listed in Flora 

Helvetica. The plant status and life form for each species have been extracted from the 

information provided by Lauber and Wagner (1998). 

The Swiss flora of vascular plants includes some 162 families and over 3000 taxa 

(species, subspecies and lower taxa). Of these, 20 plant families and 84 plant taxa 

belong to the ferns and fern allies (Pteridophyta) while the other families and taxa 

belong to the flowering plants (Spermatophyta). 

The Swiss flora comprises 2505 native species belonging to 136 families (Table 10.1; 

excluding subspecies and lower taxa). From the 470 taxa of alien origin recorded in 

Switzerland, over 100 species are cultivated species that are not, or rarely, found in the 

environment. The 362 remaining alien species have become subspontaneous, adventive 

or naturalized. These alien species, which represent about 12.6 % of the flora of Switzerland, 

are discussed below. 

This percentage is similar to that observed in neighbouring countries, e.g. 9.1 % in 

Austria, 10.2 % in France, but much less than in countries in North America, e.g. 28 % 

in Canada, or on islands, e.g. 47 % in New Zealand (Heywood, 1989). The density of 

alien species in Switzerland (i.e. the number of alien species per log country size in


10.3 

square kilometres) is 78.4 and slightly higher than in several other European countries. 

This may be due to the topography and diversity of climates encountered in Switzerland 

which allow plant species as different as Agave americana L. and Reynoutria 

japonica Houttuyn to become naturalized (see also Weber, 1999a, b). France, which 

offers an even wider range of habitats and climates, has a density of alien species of 

87.1 (Heywood, 1989), whereas in Austria, the density of alien species is 60.9. 

According to Lauber and Wagner (1998), the group containing ferns and its allies does 

not include any alien species (Table 10.1). There is a high proportion of alien gymnosperm 

species (28.6 %), i.e. four alien gymnosperm species out of 14 recorded. The 

frequency of alien species in the dicotyledons and monocotyledons is quite similar, i.e. 

13.5 % and 11.0 %, respectively. 

Tab. 10.1 > Synopsis of the native and alien flora of Switzerland: number of species (% of total). 

Pteridophyta Spermatophyta Total 

Gymnosperms Dicotyledons Monocotyledons 

Native species* 

84 (3.4) 

10 (0.4) 

1879 (75.0) 

532 (21.2) 

2505 (100) 

Families 

20 (14.7) 

4 (2.9) 

93 (68.4) 

19 (14.0) 

136 (100) 

Alien species** 

0 

4 (1.1) 

292 (80.7) 

66 (18.2) 

362 (100) 

Families which include alien spp. 

0 

2 (2.5) 

64 (80.0) 

14 (17.5) 

80 (100) 

TOTAL no. species 84 (2.9) 14 (0.5) 2171 (75.7) 598 (20.9) 2867 (100) 

% alien species / total no. species 0 28.6 13.5 11.0 12.6 

* Excluding subspecies and varieties 

** Excluding cultivated species which are not, or only rarely, found in the environment 

The geographic origin of alien and naturalized species 

About one-fifth of all alien plant species in Switzerland have been introduced from 

each of the following areas: North America, Asia and the Mediterranean (Fig. 10.1; 

Table 10.2). Some 15 % have been introduced from the rest of Europe and Eurasia/the 

Caucasus. The distribution of the so-called Eurasian species usually extends from 

eastern and south-eastern Europe to Asia Minor. Approximately one-fifth of the species 

of Asian origin were restricted to western Asia and the other four-fifths to Central 

Asia, China and east Asia. Only three species originate from Africa, three from Central 

America and 14 from South America (Table 10.6). One species is native to Australia. 

Seven per cent of all alien species in Switzerland are of unknown origin. 

One hundred and two alien species have become naturalized. Although 71 alien plant 

species in Switzerland have been introduced from North America and 76 from the 

Mediterranean region, only 18.4 % from the Mediterranean region have become naturalized 

whereas 43.7 % of those of North American origin have done so. Also, 31.1 % 

of the alien species of European origin have become naturalized but only 25.8 % of 

those of Asian/Eurasian origin. It should be noted that three out of five species introduced 

from the Caucasus have become naturalized and two of them are considered to 

be invasive (Heracleum mantegazzianum and Rubus armeniacus Focke).


Tab. 10.2 > The origin of the alien flora of Switzerland: number of species (%). 

North America 

South America Asia Eurasia/Caucasus Europe Mediterranean. Others Unknown Total 

Alien 71 (19.6) 14 (3.9) 68 (18.8) 56 (15.5) 45 (12.4) 76 (21.0) 7 (1.9) 25 (6.9) 362 (100) 

Naturalized 31 (30.4) 3 (2.9) 17 (16.7) 15 (14.7) 14 (13.7) 14 (13.7) 3 (2.9) 5 (4.9) 102 (100) 

Invasive 8 (40.0) 1 (5.0) 8 (40.0) 2 (10.0) 0 0 1 (5.0) 0 20 (100) 

Fig. 10.1 > The origin of alien plants in Switzerland. 

Mediterranean 

21% 

Europe 

12% 

Eurasia/ 

Caucasus 

16% 

Asia 

19% 

Others/ 

unknown 

13% 

North America 

20% 

Fig. 10.2 > The origin of naturalized species in Switzerland. 

Mediterranean 

14% 

Europe 

14% 

Eurasia/ 

Caucasus 

15% 

Others/ 

unknown 

11% 

In total, 30.4 % of the naturalized flora originates from North America and 31.4 % from 

Eurasia and the Caucasus (Fig. 10.2; Table 10.2). 

Of the 20 species that are considered to be invasive in Switzerland (http://www.cpsskew.ch/), 

40 % originate each from North America and Asia (Table 10.2). With the 

exception of the Caucasian species, no Eurasian or Mediterranean species have become 

invasive. One might argue that Eurasian and Mediterranean species capable of being 

invasive in Switzerland will have arrived already. Thus, not surprisingly, the majority 

of naturalized and invasive species in Switzerland originate from temperate North 

America and Asia. Europe and the Mediterranean are a major source of alien species, 

but interestingly not of naturalized or invasive plants. 

Pathways of introduction 

From the 20 species on the Black List of invasive species (http://www.cps-skew.ch/), 

15 (75 %) have been deliberately introduced, usually as ornamentals. The pathway of 

introduction of the two aquatic species, Elodea canadensis Michaux and E. nuttallii 

(Planchon), is unknown but they might well have escaped from garden ponds or been 

released from aquariums and thus are likely to be deliberate introductions as well. 

Kowarik (2003) separates the pathways of the 25 problematic species in Germany into 

21 deliberate (84 %) and four accidental (16 %) introductions. These figures are summarized 

in Table 10.3 together with the corresponding numbers of the total neophytes 

in Austria and the Czech Republic. 

Asia 

17% 

North America 

30%


10.4 

These two sets of data each give a similar picture for the Central European flora. The 

total numbers of neophytes in Austria and the Czech Republic are around 1,000 species 

and the numbers of problematic species in Germany and Switzerland are 25 and 27, 

respectively. It should be noted that the figure of 1,000 neophytes given by Essl and 

Rabitsch (2002) for Austria is much higher than the 300 introduced species given by 

Heywood (1989) for the same country. 

The percentage of deliberate introductions that have become problematic is between 

75 % and 84 %, while it is lower for all neophytes, i.e. between 55 % and 59 %. The 

comparison indicates that species selected for introduction are more likely to become 

problematic species than those arriving accidentally. These differences may be attributed 

to human dimensions in the success of invasions, in particular propagule pressure. 

Tab. 10.3 > Pathways of introductions into four European countries. 

The numbers for Switzerland and Germany are based on problematic plants (authors’ data and 

Kowarik, 2003), while the numbers for Austria (Essl and Rabitsch, 2002) and Czech Republic 

(Pysek et al., 2002) are neophytes. 

Switzerland 

Germany Austria Czech Republic 

Total number 20 25 1110 924 

Deliberate 15 21 652 504 

Accidental 4 4 372 420 

Unknown 1 - 86 - 

Deliberate/Accidental as percentage of total 75 / 25 84 / 16 59 / 33 55 / 45 

Status of the alien species of Switzerland 

Of the 362 alien species recorded in Switzerland, 102 species (28.2 %) have become 

naturalized and 20 species have become invasive (5.5 %) (Fig. 10.3), which also means 

that a quarter of all naturalized species have become invasive. The remaining species 

are either adventive or subspontaneous, or of unknown status. Thus, 3.6 % of the Swiss 

flora consists of naturalized species. 

The 362 alien species belong to 80 plant families, i.e. about half of all plant families 

present in Switzerland (Table 10.1). The percentage of alien species per family ranges 

from 2.8 % (Juncaceae) to 100 % for 20 plant families which are represented by alien 

species only, usually by one or two species (Table 10.7). The percentage of alien 

species in the large families (>30 species) ranges from 2.8 (Juncaceae) to 25.6 % 

(Polygonaceae). The largest family, Asteraceae, comprises 340 species of which some 

12.4 % are alien species. Thirty percent of all alien species belong to the Asteraceae, 

Brassicaceae and Poaceae. 

Some 50 plant families in Switzerland include no alien species. Most of these are small 

or very small families. Exceptions are the Orchidaceae (62 species), Gentianaceae (34 

species), Potamogetonaceae (21 species) and Orobanchaceae (20 species).


Fig. 10.2 > Status of alien species in Switzerland. 

Unknown 

22% 

Invasive 

5.5% 

Naturalized 

28% 

Adventive 

22% 

Subspont. 

28% 

10.5 Naturalized species of Switzerland 

Naturalized species are represented by 102 species belonging to 49 plant families, i.e. 

less than one-third of the total number of families in Switzerland (Table 10.7). The 

majority (30 families) include only one naturalized species. Eleven families include 

two naturalized species, and only eight families have more than two naturalized species. 

The Asteraceae alone includes ten naturalized species followed by the Rosaceae 

(nine), the Brassicaceae (seven) and the Fabaceae (six). Almost one-third of all naturalized 

species belong to one of these four families. 

The percentage of naturalized species per family ranges from 0.8 % (Caryophyllaceae) 

to 100 % for eight families that are represented exclusively by their naturalized species 

(usually one species – with the exception of the Phytolaccaceae which is represented 

by two species) (Table 10.7). The percentage of naturalized species in the large families 

(>30 species) ranges from 0.8 % (Caryophyllaceae) to 7.7 % (Polygonaceae). The 

largest family, Asteraceae, comprises 2.9 % naturalized species. The aquatic plant 

family Hydrocharitaceae comprises 71.4 % naturalized species. 

Fig. 10.3 > Number of established species as a function of the number of alien species (r 2 =0.8). 

No. of naturalized species / 

family 

12 

10 

8 

6 

4 

2 

0 

0 5 10 15 20 25 30 35 40 

No. of exotic species / family


In total, 28.2 % of all alien species have become naturalized. No naturalization at all is 

observed in 31 families (comprising 55 alien species). The highest rate of failure is in 

the Amaranthaceae with nine alien but no naturalized species. In contrast, 100 % 

naturalization is observed in 17 families accounting for 20 alien species. The number 

of naturalized species is correlated to the number of species introduced (Fig. 10.4). 

10.6 Life form 

The 11 life forms that are defined in Flora Helvetica (see also Table 10.6) have been 

pooled into eight different ones. The categories ‘trees’ and ‘shrubs’ include both 

deciduous and evergreen plants. The category ‘small shrubs’ includes both woody and 

herbaceous chamaephytic plants. Chamaephytic plants are perennial species with 

persistent stems and buds overwintering above ground level. Geophytic plants are 

perennial herbs with tubers, bulbs or rhizomes. 

In all, 46.4 % of the alien flora of Switzerland consists of annual and biennial species 

(n=168) but only 21.6 % of the naturalized flora is in these groups (n=22) (Table 10.4). 

In contrast, perennial species form 53.6 % of the alien flora but 78.4 % of the naturalized 

flora. Thus, of the alien species present in Switzerland, relatively more aquatic 

plants (78 %), small shrubs (55 %) and trees (47 %), and indeed perennial plants as a 

whole (41 %) have become naturalised, compared to biennial plants (13 %) and annual 

herbs (13 %). 

Tab. 10.4 > The life form of vascular plants in Switzerland: number of species (% of total). 

Life forms Alien species Naturalized species Invasive species Native species 

Perennials Trees 30 (8.3) 14 (13.7) 5 (25.0) 68 (2.7) 

Shrubs 25 (6.9) 8 (7.8) 2 (10.0) 103 (4.1) 

Small shrubs 22 (6.1) 12 (11.8) 0 238 (9.6) 

Geophytic plants 48 (13.3) 18 (17.6) 7 (35.0) 383 (15.4) 

Herbs 60 (16.6) 21 (20.6) 1 (5.0) 1120 (44.9) 

Aquatic plants 9 (2.5) 7 (6.9) 2 (10.0) 62 (2.5) 

Perennials (total) 194 (53.6) 80 (78.4) 17 (85) 1974 (79.1) 

Biennial herbs 54 (14.9) 7 (6.9) 1 (5.0) 239 (9.6) 

Annual herbs 114 (31.5) 15 (14.7) 2 (10.0) 279 (11.2) 

Total 362 102 20 2492 

Woody and geophytic plants account for 70 % of invasive species in Switzerland 

(Table 10.4). Perhaps surprisingly, no chamaephytic and only one herbaceous perennial 

have become invasive. The proportions of shrubs and aquatic plants in the invasive 

flora are similar, as are the proportions of these two life forms in the naturalized flora, 

i.e. 7–10 %. Thus, there are again a disproportionate number of large woody perennials


and geophytic species that have become invasive compared to those that have become 

naturalized. Only few short-lived species have become invasive. 

In total, 85 % of the invasive flora in Switzerland consists of perennial species of which 

more than two-thirds are trees and geophytic plants. The proportion of alien species 

that are trees is three times the proportion of native species that are trees (Table 10.4), 

but the proportion of invasive species that are trees is about ten times the figure for 

native species. For comparison, the proportion of short-lived plants that are alien is 

about twice the proportion for native species, but the proportions of short-lived species 

that are invasive and native are similar. In contrast, the proportion of herbaceous 

perennials that are native is almost three times higher than the figure for alien species 

and nearly ten times higher than for invasive species (Table 10.4). In summary, the life 

form composition of the alien flora is different from the native one and it changes 

during the process of naturalization and invasion. While the highest number of introduced 

species are annual plants, they do not naturalize well. The relatively small 

number of introduced trees and geophytic plants are successful in the naturalization 

process and are aggressive invaders. The introduction, naturalization and invasion of 

alien plant species results not only in a change in the floristic composition, but also in 

plant life form changes with probable consequences on habitat structure and ecosystem 

functioning. 

10.7 The habitats of alien plants in Switzerland 

The ecological plant groups used here have been taken from Lauber and Wagner 

(1998) to define plant habitats. Nine ecological groups have been defined: 

> F = forest plant 

> M = mountain plant 

> P = (lowland) pioneer plant 

> E = aquatic plant 

> H = marsh plant 

> S = dry grassland plant 

> G = grassland plant 

> R = ruderal plant 

Tab. 10.5 > The ecological groups of alien plants in Switzerland, excluding cultivated plants: 

number of species (%). 

Forest 

Mountain Pioneer Aquatic Marsh Dry grassland Grassland Ruderal Total 

Alien 34 (11.3) 4 (1.3) 19 (6.3) 12 (4.1) 26 (8.6) 14 (4.7) 4 (1.3) 189 (62.6) 302 

Naturalized 23 (23.5) 3 (3.1) 11 (11.2) 8 (8.2) 11 (11.2) 4 (4.1) 0 38 (38.8) 98 

Invasive 3 (15.0) 0 7 (35.0) 2 (10.0) 3 (15.5) 0 0 5 (25.0) 20 

Native 443 (17.9) 644 (26.0) 126 (5.1) 96 (3.9) 308 (12.4) 347 (14.0) 74 (3.0) 438 (17.7) 2476


The majority of alien species in Switzerland are ruderal plants (62.6 %), followed by 

forest plants (11.3 %) and marsh plants (8.6 %) (Table 10.5). However, ruderal plants 

represent only 38.8 % of all naturalized species. Forest species increase to 23.5 % of all 

naturalized species, followed by pioneer and marsh species (11.2 %), and aquatic 

species (8.2 %). There are very few mountain and grassland species naturalized in 

Switzerland. Thus, it appears that forest and wetland habitats are more suited to plant 

naturalization since 42.9 % of all naturalized species belong to these ecological groups 

(F, E, H). It should be noted, however, that three out of four mountain species have 

become naturalized. Only 20.2 % of ruderal species have become naturalized. 

Ruderal and pioneer species represent 60 % of all invasive species, indicating perhaps 

less resistance of these habitats to invasion. Wetlands and forests seem to be more 

resistant to invasion. However, 40 % of invasive species in Switzerland belong to either 

the forest, aquatic or marsh ecological plant groups (F, E, H) and thus are a potential 

threat to the most valuable ecosystems of Switzerland, i.e. forests and wetland habitats. 

Mountain and grassland habitats seem to be at less risk based on invasions to date. 

About 50 % of all naturalized and invasive species are ruderal and lowland pioneer 

species. These species are often not restricted to waste ground or urban areas, but are 

known to invade (sometimes after a long period) semi-natural habitats such as meadows, 

riverbanks, gravel shores, forest margins or clearings. Several of the worst invasive 

plants in Switzerland such as Reynoutria japonica, Heracleum manteggazianum, 

Impatiens glandulifera Royle, Buddleja davidii Franchet and Solidago canadensis L. 

are treated as ruderal or pioneer plants but are known to invade less disturbed places as 

well. Solidago spp. in particular have been recognized for over a decade as a threat to 

protected areas (Voser-Huber, 1992). Impatiens parviflora DC. was introduced from 

Asia into Central Europe in 1837 and was for many years a typical ruderal plant occurring 

only in towns, gardens, parks or cemeteries. A few decades ago, however, it 

started to penetrate into woods, at first only in badly degraded areas, but then becoming 

firmly established in relatively natural stands of deciduous forests in Central Europe 

(Kornas, 1990). 

Weber (1999a) gives the number of alien plant species recorded in various habitats 

(s.str.) in Switzerland: 16 % are known from forests and related habitats, 15 % from 

lakes and wetland areas, and 8 % from grassland habitats. Interestingly, 16 % of alien 

plants are found in rocky sites and on walls. As compared to the 61 % of ruderal species, 

some 35 % of alien plants grow only in ruderal sites. The number of alien plants 

recorded in various habitats is relatively similar to the numbers that can be extrapolated 

from the ecological groups. The data suggest that many ruderal alien plants are not 

restricted to ruderal sites but grow mainly in open habitats or less disturbed sites such 

as rocky areas, walls, or forests subjected to some disturbance. 

As shown above, the great majority of naturalized and invasive species in Switzerland 

are perennial species and most of them are forest, wetland and ruderal species. With 

very few exceptions (e.g. Impatiens glandulifera), naturalized and invasive short-lived 

species are uncommon in semi-natural or natural habitats.


With respect to plant life form, the composition of the ecological plant groups of the 

alien flora differs from the native one, and it changes during the process of naturalization 

and invasion. The proportion of ruderal species in the alien flora is much higher 

than in the native one but this discrepancy is reduced during the naturalization process. 

In contrast, the proportion of alien forest plant species is lower than that of native 

forest plant species but proportions of invasive and native forest plant species are fairly 

similar. 

10.8 Invasive plant species in Europe 

Up to 2003, only a few European countries had compiled data on their alien and invasive 

floras at a national level. However, information from several countries is quite 

informative about invasive species elsewhere in Europe that could be a threat to Switzerland. 

Countries usually make explicit distinctions between invasive species, moderately 

or potentially invasive species, and species for which special attention is needed 

(usually the so-called ‘Watch List’). We had to interpret some data to a certain extent 

to obtain a more consistent result. Austria includes an assessment of economic impact, 

which we have reproduced in Table 10.8 (Essl and Rabitsch, 2002). Also, the European 

and Mediterranean Plant Protection Organization (EPPO) is preparing a list of invasive 

and potentially invasive alien plants for the EPPO region. This information is still 

partial and it has not been used for the present review. 

Plant species declared invasive or potentially invasive in nine European countries and 

occurring in Switzerland are presented in Table 10.8. The list includes over 130 alien 

plant species of concern in Europe. Quite obviously, not all of them are sufficiently 

pre-adapted to the eco-climatic conditions of Switzerland to present a threat in this part 

of Europe. On the other hand, some invasive species in northern European countries, 

for example, which are not listed in Table 10.8, could become a problem in Switzerland. 

Unfortunately, no detailed list of alien plants in Germany for each of the three 

categories defined was available at the time of this review. In contrast, the detailed 

information on the status of alien plants in France is highly relevant to Switzerland 

(Muller, 2004). 

The list of invasive species (‘Black List’) and ‘Watch Species’ in Switzerland is taken 

from the CPS-SKEW working group (http://www.cps-skew.ch/index.htm). A few 

species in these two categories do not have this status in the other European countries 

from which information could be collected (Table 10.8). However, they are invasive on 

other continents, e.g. Pueraria lobata (Willd.), and Lonicera japonica Thunberg 

(Cronk and Fuller, 1995; Weber, 2003) or their taxonomy is complex and their invasive 

status may not yet have been recognized (e.g. Rubus armeniacus). 

Fact Sheets have been prepared for 48 plant species. They include 19 invasive species 

and 11 ‘Watch Species’ of the CPS-SKEW working group. In this report, another 18 

species to which special attention should be given in the future are also presented in 

Fact Sheets. These species have been selected according to their status in neighbouring 

countries and a previous list of potentially invasive species prepared by the CPS- 

SKEW working group (Table 10.8).


10.9 Discussion 

About 362 alien species are established in Switzerland and almost one third of these 

have become naturalized with certainty. With the exception of aquatic plants in the 

Hydrocharitaceae, no one plant family appears to be particularly successful in naturalization. 

This review stresses the importance of establishing the biological and ecological 

characteristics of the naturalized flora for determining the potential invasiveness of 

alien species in Switzerland. The life form composition of the alien flora is different 

from that of the native one and changes during the process of naturalization from 

dominance by short-lived to perennial species. The flora of naturalized plants consists 

of almost 80 % perennial species. There is a further shift during the process of invasion 

towards large woody perennial and geophytic plants. The invasion by herbaceous 

perennials and short-lived plants has been negligible so far. Invasive species come 

from geographically distant areas and no European or Mediterranean species is considered 

to be invasive or potentially invasive in Switzerland. 

More than 40 % of all naturalized and invasive species consist of either forest or wetland 

species, thus it appears that these habitats are at a higher risk of invasion. In 

Europe, over 50 % of the naturalized flora occurs in river border communities (Sykora, 

1990). This is because rivers are an effective means of transportation for many species, 

natural riverbank communities have been largely destroyed by human activities, and 

riverbanks are regularly disturbed by water movement. Alluvial zones and mires are 

therefore of primary concern with regard to invasive species. The typical vegetation of 

lowland alluvial zones such as riverine floodplains consists of a mosaic of pioneer 

communities, shrubs and alluvial forests. Invasion by pioneer or ruderal alien species is 

likely to occur and expand in such sites due to human activities or colonization from 

upstream or adjacent fields. Fenlands also are at risk because they are often used for 

agricultural purposes. In contrast, raised bogs are at a lower risk since only highly 

specialized plant species can flourish in such habitats, and there is less permanent 

natural disturbance. 

To date, the invasibility of mountain and grassland habitats has been low and few alien 

species have become naturalized in these habitats. Because meadows and grasslands 

owe their existence almost exclusively to human management, the threat from alien 

species will increase with land-use changes and reduced grassland maintenance. In the 

absence of any management, most meadows and grasslands below the timberline 

degenerate to scrub and revert to woodland. Alien shrubs and trees may profit from 

such a situation. 

The restoration of biological diversity in intensively used agricultural land has been 

supported for several years through various agri-environmental schemes. In many areas 

this involves the conversion of intensively managed arable land to extensive pastures 

or so-called areas of ecological compensation. The transition period from intensively to 

extensively managed land or semi-natural habitats is highly favourable to alien species.


Alien plants are a threat to the areas of ecological compensation, the restoration of 

riverbanks and mires, abandoned grassland and forests, and all previously or currently 

disturbed natural areas in Switzerland. For example, the rehabilitation of riverbanks 

can be seriously handicapped by alien species. Many invasive species increase erosion 

(e.g. Reynoutria japonica, Buddleja davidii), which in turn accelerates the establishment 

of invasive species, thus preventing the restoration of native plant communities. 

The problems caused by alien species in cultivated land are still relatively minor but 

may increase in the future because of newly naturalized species and because changes in 

land use may favour establishment of alien species in extensive agro-ecosystems. 

Weber (1999a) recorded 38 alien plants that are known to occur in arable land. For 

example, Conyza canadensis (L.) and Epilobium ciliatum Rafinesque are of increasing 

importance in arable land, gardens, orchards and tree nurseries. Galinsoga parviflora 

Cavanilles is known to be a serious problem in vegetable crops in other countries and 

Cyperus esculentus is considered to be one of the world’s worst weeds. Ambrosia 

artemisiifolia is most abundant in sunflower crops owing to the botanical similarity 

between the weed and the crop itself, and therefore only a limited number of herbicides 

are available that are effective against A. artemisiifolia alone. Senecio inaequidens is a 

potential problem in pastures and meadows. Unlike those in a natural environment, 

most alien plants in arable land are ruderal species and the majority of them are short 

lived. 

Alien species can also become a public health problem. Ambrosia artemisiifolia is a 

strongly allergenic plant. Exposure to the sap of Heracleum manteggazianum sensitizes 

the skin to sunlight and causes severe irritation and painful blisters. Contact with the 

sap of Ailanthus altissima (Miller) may also cause skin eruptions. 

Most of the 20 declared invasive plants in Switzerland are also invasive in neighbouring 

countries. An analysis of the invasive flora of several European countries shows 

that over 130 alien plants are of concern in Europe. The status of alien plants in Europe 

should be one aspect considered in developing a dynamic ‘Watch List’ of alien plants 

in Switzerland. In addition to the known invasive species of Switzerland, over 30 alien 

plants should be monitored over time to predict their invasive potential. 

In conclusion, a careful review of invasive and potentially invasive plants in Europe 

combined with some key biological and ecological traits associated with naturalized 

species rather than alien plants, as well as field observations, should contribute to 

assessing the invasiveness of alien plant species in Switzerland. More research is 

needed to understand the naturalization and invasion process and to evaluate the impact 

of invasive species on the environment and the agro-ecosystem. More research is also 

needed to establish long-term and environmentally friendly management tools for 

invasive plants in Switzerland.


References 

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pp. 

Dana, E.D., Sanz-Elorza, M. and E. Sobrino (2001) Plant invaders in 

Spain. http://www.ual.es/personal/edana/alienplants/checklist.pdf 

De Almeida, J.D. (1999) Flora exotica subespontanea de Portugal 

continental. Universidade de Coimbra, 151 pp. 



Heywood, V.H. (1989) Patterns, extends and modes of invasions by 

terrestrial plants. In: Drake, J.A. et al. (eds) Biological invasions: a global 

perspective. SCOPE 37, John Wiley & Sons, pp. 31–55. 

Kornas, J. (1990) Plant invasions in Central Europe: historical and 

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1616 pp. 

Moser, D.M., Gygax, A., Bäumler. B., Wyler, N. and R. Palese (2002) Rote 

Liste der gefährdeten Farn- und Blütenpflanzen der Schweiz. BUWAL- 

Reihe ”Vollzug Umwelt“. 

Muller, S. (2004) Plantes invasives en France. Paris, Muséum National 

d’Histoire Naturelle. Patrimoines naturels, 62, 176 pp. 

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and definitions. Diversity and Distributions 6, 93–107. 

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naturelles. OFEFP, Cahier de l’environnement N° 167, 22 pp. 

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110, 11–24. 

Weber, E (1999b) Gebietsfremde Arten der Schweizer Flora – Ausmass 

und Bedeutung. Bauhinia 13, 1–10. 

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environmental weeds. CABI Publishing, Wallingford, 548 pp. 

Welch, D. et al. (2001) An audit of alien species in Scotland. Scottish 

Natural Heritage Review No 139, 225 pp.


Tab. 8.6 > Alien species in Switzerland. 

Species 

Family Origin Life form Status Ecol. group 

Abutilon theophrasti Medic. Malvaceae Unknown t adventive N R 

Acalypha virginica L. Euphorbiaceae North America t naturalized N R 

Acer negundo L. Aceraceae North America t subspontaneous F 

Acorus calamus L. Araceae Unknown g unknown N E 

Aegilops cylindrica Host Poaceae Mediterranean t adventive R 

Aegilops ovata L. Poaceae Mediterranean t adventive R 

Agave americana L. Agavaceae Central America j naturalized N R 

Ailanthus altissima (Miller) Simaroubaceae Asia p naturalized N P 

Aldrovanda vesiculosa L. Droseraceae Unknown a unknown N E 

Allium scorodoprasum L. Liliaceae Europa g unknown N R 

Alopecurus rendlei Eig Poaceae Mediterranean t adventive H 

Althaea officinalis L. Malvaceae Asia h subspontaneous C 

Amaranthus albus L. Amaranthaceae North America t unknown N R 

Amaranthus blitum L. Amaranthaceae Unknown t unknown N R 

Amaranthus cruentus L. Amaranthaceae North America t subspontaneous N R 

Amaranthus deflexus L. Amaranthaceae South America u unknown N R 

Amaranthus graecizans L. Amaranthaceae Unknown t unknown N R 

Amaranthus hypochondriacus L. Amaranthaceae Unknown t unknown N R 

Amaranthus retroflexus L. Amaranthaceae Unknown t unknown N R 

Ambrosia artemisiifolia L. Asteraceae North America t adventive N R 

Amorpha fructicosa L. Fabaceae North America n subspontaneous N H 

Arabis rosea DC. Brassicaceae Europa h naturalized N P 

Arabis caucasica (Willdenow) Brassicaceae Eurasia c naturalized N M 

Aremonia agrimonioides (L.) Rosaceae Europa h naturalized N P 

Armoracia rusticana P.Gaertn., B. Mey. & Scherb. Brassicaceae Eurasia g subspontaneous C 

Artemisia annua L. Asteraceae Eurasia t adventive R 

Artemisia biennis Willdenow Asteraceae Eurasia u adventive R 

Artemisia verlotiorum Lamotte Asteraceae Asia g unknown N R 

Arum italicum Miller Araceae Mediterranean g naturalized R 

Asarina procumbens Mill. Scrophulariaceae Mediterranean c naturalized N P 

Asclepias syriaca L. Asclepiadaceae North America g subspontaneous N CR 

Aster novae-angliae L. Asteraceae North America g subspontaneous N H 

Aster novi-belgii L. Asteraceae North America c subspontaneous N H 

Aster tradescantii L. Asteraceae North America g subspontaneous C 

Aubrieta deltoidea (L.) Brassicaceae Mediterranean c naturalized N S 

Avena barbata Pott Poaceae Mediterranean t adventive R 

Avena sativa L. Poaceae Eurasia t subspontaneous C 

Bidens bipinnata L. Asteraceae North America t naturalized N R 

Bidens connata Willdenow Asteraceae North America t naturalized N H 

Bidens frondosa L. Asteraceae North America t naturalized N R


Species 


Bidens subalternans DC. Asteraceae South America t adventive R 

Brassica juncea (L.) Brassicaceae Asia t adventive R 

Brassica nigra (L.) Brassicaceae Unknown t naturalized R 

Brassica rapa L. Brassicaceae Europa u subspontaneous C 

Bromus diandrus Roth Poaceae Europa t adventive R 

Bromus inermis Leysser Poaceae Eurasia h unknown N R 

Bromus madritensis L. Poaceae Mediterranean t adventive R 

Bromus rigidus Roth Poaceae Mediterranean t adventive R 

Buddleja davidii Franchet Buddlejaceae Asia n naturalized N P 

Bunias orientalis L. Brassicaceae Eurasia h unknown N R 

Calla palustris L. Araceae Unknown g naturalized N E 

Cannabis sativa L. Cannabaceae Asia t subspontaneous C 

Carex vulpinoidea Michaux Cyperaceae North America h naturalized N H 

Centaurea diffusa Lamarck Asteraceae Mediterranean t adventive R 

Centranthus ruber (L.) Valerianaceae Mediterranean h naturalized N P 

Cerastium dubium (Bastard) Caryophyllaceae Mediterranean t adventive H 

Cerastium ligusticum Viviani Caryophyllaceae Mediterranean t adventive R 

Cerastium tomentosum L. Caryophyllaceae Europa c subspontaneous C 

Cerinthe major L. Boraginaceae Eurasia t adventive R 

Cerinthe minor L. Boraginaceae Eurasia u adventive R 

Chenopodium ambrosioides L. Chenopodiaceae South America t adventive R 

Chenopodium pratericola Rydberg Chenopodiaceae North America t adventive R 

Chrysanthemum segetum L. Asteraceae Mediterranean t unknown N R 

Commelina communis L. Commelinaceae Asia c naturalized N R 

Consolida ajacis (L.) Ranunculaceae Eurasia t subspontaneous C 

Conyza canadensis (L.) Asteraceae North America u unknown N P 

Cornus sericea L. Cornaceae North America n naturalized N F 

Coronopus didymus (L.) Brassicaceae South America u adventive N R 

Crepis nemauensis Gouan Asteraceae Mediterranean t naturalized N R 

Crepis nicaeensis Persoon Asteraceae Mediterranean u adventive R 

Crepis pulchra L. Asteraceae Mediterranean t unknown N R 

Cuscuta campestris Yuncker Cuscutaceae North America t adventive N R 

Cuscuta cesatiana Bertoloni Cuscutaceae Eurasia t unknown N R 

Cymbalaria muralis P. Gaertn., B. Mey. & Scherb. Scrophulariaceae Europa c unknown N P 

Cynodon dactylon (L.) Poaceae Mediterranean g naturalized N R 

Cyperus eragrostis Lamarck Cyperaceae South America h unknown H 

Cyperus esculentus L. Cyperaceae Unknown g unknown N H 

Cyperus rotundus L. Cyperaceae Eurasia g naturalized H 

Datura stramonium L. Solanaceae Central America t unknown N R 

Dianthus barbatus L. Caryophyllaceae Europa h subspontaneous C 

Diplotaxis erucoides (Torner) Brassicaceae Mediterranean u adventive R 

Dipsacus laciniatus L. Dipsacaceae Mediterranean u unknown N R


Species 


Duchesnea indica (Andrews) Rosaceae Asia h naturalized N F 

Eleusine indica (L.) Poaceae Unknown t naturalized N R 

Elodea canadensis Michaux Hydrocharitaceae North America a unknown N E 

Elodea densa (Planchon) Hydrocharitaceae South America a naturalized N E 

Elodea nuttallii (Planchon) Hydrocharitaceae North America a naturalized N E 

Epilobium ciliatum Rafinesque Onagraceae North America h unknown N R 

Epimedium alpinum L. Berberidaceae Europa g naturalized N F 

Eragrostis cilianensis (Allioni) Poaceae Mediterranean t unknown N R 

Eragrostis multicaulis Steudel Poaceae Asia t adventive R 

Eranthis hyemalis (L.) Ranunculaceae Europa g subspontaneous N F 

Erica tetralix L. Ericaceae Europa z naturalized N H 

Erigeron annuus (L.) Asteraceae North America u naturalized N R 

Erigeron karvinskianus DC. Asteraceae Central America h unknown N P 

Erodium ciconium (L.) Geraniaceae Mediterranean t adventive R 

Erodium moschatum (L.) Geraniaceae Mediterranean u unknown N R 

Erysimum cheiri (L.) Brassicaceae Mediterranean c naturalized C 

Erysimum hieraciifolium L. Brassicaceae Eurasia u unknown N R 

Erysimum repandum L. Brassicaceae Europa t adventive R 

Euclidium syriacum (L.) Brassicaceae Eurasia t adventive R 

Euphorbia chamaesyce L. Euphorbiaceae Eurasia t adventive R 

Euphorbia humifusa Willdenow Euphorbiaceae Asia t unknown N R 

Euphorbia lathyris L. Euphorbiaceae Eurasia u subspontaneous N R 

Euphorbia maculata L. Euphorbiaceae North America t unknown N R 

Euphorbia nutans Lagasca Euphorbiaceae North America t unknown N R 

Euphorbia prostrata Aiton Euphorbiaceae North America t adventive R 

Euphorbia virgata Waldstein et Kitaibel Euphorbiaceae Eurasia h unknown N R 

Fagopyrum esculentum Moench Polygonaceae Asia t subspontaneous RC 

Fagopyrum tataricum (L.) Polygonaceae Asia t unknown R 

Ficus carica L. Moraceae Mediterranean p subspontaneous C 

Foeniculum vulgare Miller Apiaceae Mediterranean u naturalized N R 

Galega officinalis L. Fabaceae Mediterranean h subspontaneous N G 

Galinsoga ciliata (Rafinesque) Asteraceae South America t unknown N R 

Galinsoga parviflora Cavanilles Asteraceae South America t unknown N R 

Galium saxatile L. Rubiaceae Europa c unknown N H 

Galium verrucosum Hudson Rubiaceae Mediterranean t adventive S 

Geranium sibiricum L. Geraniaceae Asia u unknown N F 

Glaucium corniculatum (L.) Papaveraceae Mediterranean t adventive P 

Glaucium flavum Crantz Papaveraceae Europa u adventive P 

Glyceria striata (Lamarck) Poaceae North America g unknown N H 

Gypsophila paniculata L. Caryophyllaceae Eurasia c naturalized N P 

Helianthus annuus L. Asteraceae North America t subspontaneous C 

Helianthus rigidus (Cassini) Asteraceae North America g subspontaneous C


Species 


Helianthus tuberosus L. Asteraceae North America g subspontaneous N R 

Hemerocallis fulva (L.) Liliaceae Asia g naturalized N R 

Heracleum mantegazzianum Sommier & Levier Apiaceae Caucasus h naturalized N R 

Hibiscus trionum L. Malvaceae Asia t subspontaneous C 

Hordeum distichon L. Poaceae Western Asia t subspontaneous C 

Hordeum vulgare L. Poaceae Africa u subspontaneous C 

Hypericum calycinum L. Hypericaceae Eurasia z subspontaneous C 

Iberis umbellata L. Brassicaceae Mediterranean u subspontaneous PC 

Impatiens balfourii Hooker F. Balsaminaceae Asia t unknown N R 

Impatiens glandulifera Royle Balsaminaceae Asia t naturalized N R 

Impatiens parviflora DC. Balsaminaceae Asia t naturalized N F 

Inula helenium L. Asteraceae Europa h subspontaneous C 

Iris foetidissima L. Iridaceae Europa g subspontaneous N S 

Iris germanica L. Iridaceae Mediterranean g naturalized C 

Iris lutescens Lamarck Iridaceae Eurasia g subspontaneous N S 

Iris sambucina L. Iridaceae Unknown g unknown N S 

Iris squalens L. Iridaceae Unknown g subspontaneous N S 

Juncus tenuis Willdenow Juncaceae North America h unknown N R 

Lagarosiphon major (Ridley) Hydrocharitaceae South Africa a naturalized N E 

Laurus nobilis L. Lauraceae Mediterranean i naturalized N F 

Legousia hybrida (L.) Campanulaceae Mediterranean t adventive R 

Lemna minuta Humboldt et al. Lemnaceae North America a naturalized N E 

Lepidium densiflorum Schrader Brassicaceae North America u unknown N R 

Lepidium neglectum Thellung Brassicaceae North America u unknown N R 

Lepidium sativum L. Brassicaceae Western Asia t subspontaneous RC 

Lepidium virginicum L. Brassicaceae North America u unknown N R 

Lepidium latifolium L. Brassicaceae Europa h subspontaneous RC 

Leucanthemum gaudinii Della Torre Asteraceae Unknown h unknown N R 

Ligustrum lucidum Aiton Oleaceae Asia i subspontaneous C 

Linaria arvensis (L.) Scrophulariaceae Europa t adventive R 

Linaria repens (L.) Scrophulariaceae Europa h naturalized N R 

Linaria simplex (Willdenow) Scrophulariaceae Europa t adventive R 

Linaria dalmatica (L.) Scrophulariaceae Europa h naturalized N R 

Linum bienne Miller Linaceae Europa u adventive S 

Linum narbonense L. Linaceae Mediterranean h naturalized N S 

Lonicera japonica Thunberg Caprifoliaceae Asia i naturalized N F 

Lonicera henryi Hemsley Caprifoliaceae Asia i subspontaneous N F 

Ludwigia grandiflora (Michaux) Onagraceae South America a naturalized N E 

Lunaria annua L. Brassicaceae Europa u naturalized N R 

Lupinus polyphyllus Lindley Fabaceae North America h subspontaneous N F 

Mahonia aquifolium (Pursh) Berberidaceae North America j subspontaneous N FR 

Malus domestica Borkhausen Rosaceae Western Asia p subspontaneous C


Species 


Matricaria discoidea DC. Asteraceae Asia t unknown N R 

Meconopsis cambrica (L.) Papaveraceae Europa h unknown N R 

Medicago polymorpha L. Fabaceae Mediterranean u unknown N R 

Medicago sativa L. Fabaceae Mediterranean h subspontaneous C 

Melilotus indicus (L.) Fabaceae Eurasia t unknown N R 

Melilotus sulcatus Desfontaines Fabaceae Mediterranean t unknown N R 

Mespilus germanica L. Rosaceae Eurasia p naturalized C 

Mimulus guttatus DC. Scrophulariaceae North America g naturalized N H 

Muhlenbergia schreberi Gmelin Poaceae North America h unknown N R 

Narcissus incomparabilis Miller Amaryllidaceae Europa g subspontaneous C 

Narcissus medioluteus Miller Amaryllidaceae Unknown g naturalized N R 

Nigella damascena L. Ranunculaceae Mediterranean t subspontaneous C 

Nonea erecta Bernhardi Boraginaceae Asia h unknown N R 

Nonea lutea (Desrousseaux) Boraginaceae Eurasia u unknown N R 

Nymphoides peltata (Gmelin) Menyanthaceae Eurasia a naturalized N E 

Oenothera biennis L. Onagraceae North America u unknown N R 

Oenothera glazioviana Micheli Onagraceae Unknown u unknown N R 

Oenothera parviflora L. Onagraceae North America u unknown N R 

Oplismenus undulatifolius (Arduino) Poaceae Eurasia c naturalized F 

Opuntia humifusa (Rafinesque) Cactaceae North America c unknown N S 

Opuntia imbricata (Haworth) Cactaceae North America c unknown N S 

Ornithogalum nutans L. Liliaceae Eurasia g unknown N R 

Oxalis fontana Bunge Oxalidaceae Unknown u unknown N R 

Panicum capillare L. Poaceae North America t naturalized N R 

Panicum dichotomiflorum Michaux Poaceae North America t naturalized N R 

Papaver apulum Tenore Papaveraceae Mediterranean u adventive R 

Papaver croceum Ledebour Papaveraceae Asia h naturalized N M 

Papaver somniferum L. Papaveraceae Unknown t subspontaneous N R 

Parthenocissus quinquefolia (L.) Vitaceae North America p naturalized N F 

Parthenocissus tricuspidata (Siebold et Zuccarini) Vitaceae Western Asia p subspontaneous N C 

Paspalum dilatatum Poiret Poaceae South America g adventive H 

Paulownia tomentosa (Thunberg) Bignoniaceae Asia p subspontaneous N F 

Phacelia tanacetifolia Bentham Hydrophyllaceae North America t subspontaneous N R 

Phalaris canariensis L. Poaceae Mediterranean t adventive R 

Philadelphus coronarius L. Philadelphaceae Europa n naturalized N F 

Physalis alkekengi L. Solanaceae Eurasia g naturalized N R 

Physocarpus opulifolius (L.) Rosaceae North America n naturalized N F 

Phyteuma nigrum F.W. Schmidt Campanulaceae Europa h adventive F 

Phytolacca americana L. Phytolaccaceae North America h naturalized N R 

Phytolacca esculenta Van Houtte Phytolaccaceae Western Asia h naturalized N R 

Pimpinella peregrina L. Apiaceae Mediterranean t adventive R 

Pisum sativum L. Fabaceae Eurasia t naturalized N R


Species 


Plantago arenaria Waldstein et Kitaibel Plantaginaceae Eurasia t unknown N R 

Polygonum orientale L. Polygonaceae Asia t subspontaneous R 

Polygonum polystachyum Meissner Polygonaceae Asia g naturalized N R 

Polypogon monspeliensis (L.) Poaceae Eurasia t adventive R 

Pontederia cordata L. Pontederiaceae North America g adventive E 

Potentilla intermedia L. Rosaceae Europa h adventive R 

Potentilla recta L. Rosaceae Eurasia h unknown N R 

Prunus cerasus L. Rosaceae Western Asia p naturalized N F 

Prunus dulcis (Miller) Rosaceae Western Asia p naturalized N F 

Prunus laurocerasus L. Rosaceae Eurasia i naturalized N F 

Prunus serotina Ehrhart Rosaceae North America p naturalized N F 

Pseudotsuga menziesii (Mirbel) Pinaceae North America i naturalized N F 

Pueraria hirsuta (Thunberg) Fabaceae Western Asia p subspontaneous N FR 

Punica granatum L. Punicaceae Western Asia n subspontaneous C 

Pyrus pyraster (L.) Rosaceae Eurasia p subspontaneous FC 

Quercus rubra L. Fagaceae North America p naturalized N F 

Ranunculus muricatus L. Ranunculaceae Mediterranean t adventive H 

Raphanus sativus L. Brassicaceae Mediterranean u subspontaneous C 

Rapistrum perenne (L.) Brassicaceae Europa h adventive R 

Reynoutria japonica Houttuyn Polygonaceae Asia g naturalized N R 

Reynoutria sachalinensis (F. Schmidt) Polygonaceae Asia g subspontaneous N R 

Rhus typhina L. Anacardiaceae North America p naturalized N P 

Robinia pseudoacacia L. Fabaceae North America p naturalized N F 

Rorippa austriaca (Crantz) Brassicaceae Europa h adventive H 

Rosa rugosa Thunberg Rosaceae Western Asia n subspontaneous N R 

Rostraria cristata (L.) Poaceae Mediterranean h adventive R 

Rubia tinctorum L. Rubiaceae Eurasia h naturalized N R 

Rubus armeniacus Focke Rosaceae Caucasus n naturalized N F 

Rudbeckia hirta L. Asteraceae North America u subspontaneous C 

Rudbeckia laciniata L. Asteraceae North America g subspontaneous N R 

Rumex longifolius DC. Polygonaceae Eurasia h unknown N P 

Rumex palustris J.E. Smith Polygonaceae Eurasia u adventive R 

Rumex thyrsiflorus Fingerhuth Polygonaceae Eurasia h unknown N R 

Rumex confertus Willdenow Polygonaceae Asia h naturalized N P 

Salvia sylvestris L. Lamiaceae Eurasia h naturalized N R 

Salvia verbenaca L. Lamiaceae Mediterranean h adventive S 

Salvia verticillata L. Lamiaceae Mediterranean h unknown N R 

Sarracenia purpurea L. Sarraceniaceae North America h naturalized H 

Saxifraga hirsuta L. Saxifragaceae Europa h subspontaneous C 

Saxifraga stolonifera Meerburgh Saxifragaceae Western Asia h naturalized N P 

Saxifraga umbrosa L. Saxifragaceae Europa c subspontaneous C 

Scabiosa ochroleuca L. Dipsacaceae Europa h naturalized N S


Species 


Scilla non-scripta (L.) Liliaceae Europa g naturalized N F 

Scrophularia vernalis L. Scrophulariaceae Mediterranean u adventive N R 

Sedum sarmentosum Bunge Crassulaceae Asia c naturalized C 

Sedum sediforme (Jacquin) Crassulaceae Mediterranean c adventive P 

Sedum spurium M. Bieberstein Crassulaceae Western Asia c subspontaneous N R 

Sedum hispanicum L. Crassulaceae Europa u unknown P 

Senecio inaequidens DC. Asteraceae South Africa u naturalized N R 

Senecio rupestris Waldstein et Kitaibel Asteraceae Europa u unknown N R 

Setaria italica (L.) Poaceae Unknown t subspontaneous RC 

Silene conica L. Caryophyllaceae Mediterranean t adventive R 

Silene dichotoma Ehrhart Caryophyllaceae Europa u adventive R 

Sinapis alba L. Brassicaceae Mediterranean t subspontaneous RC 

Sisymbrium altissimum L. Brassicaceae Eurasia u unknown N R 

Sisymbrium irio L. Brassicaceae Mediterranean u unknown N R 

Sisymbrium loeselii L. Brassicaceae Eurasia u unknown N R 

Sisyrinchium montanum Greene Iridaceae North America h unknown N H 

Solanum sublobatum Roemer et Schultes Solanaceae South America t naturalized N R 

Solidago canadensis L. Asteraceae North America g naturalized N R 

Solidago gigantea Aiton Asteraceae North America g naturalized N H 

Solidago graminifolia (L.) Asteraceae North America g naturalized N R 

Sorghum halepense (L.) Poaceae Unknown h unknown N R 

Sorghum vulgare Persoon Poaceae Western Asia t adventive C 

Spiraea salicifolia L. Rosaceae Eurasia n subspontaneous N R 

Spiraea ulmifolia Scopoli Rosaceae Eurasia n subspontaneous N R 

Staphylea pinnata L. Staphyleaceae Eurasia n subspontaneous FC 

Stratiotes aloides L. Hydrocharitaceae Eurasia a naturalized N H 

Symphoricarpos albus (L.) Caprifoliaceae North America n naturalized N F 

Symphytum asperum Lepechin Boraginaceae Caucasus h naturalized N R 

Tanacetum cinerariifolium (Treviranus) Asteraceae Europa h naturalized N P 

Thlaspi alliaceum L. Brassicaceae Europa u naturalized N R 

Tolpis barbata (L.) Asteraceae Mediterranean t adventive R 

Tordylium maximum L. Apiaceae Mediterranean u adventive R 

Torilis leptophylla (L.) Apiaceae Mediterranean t adventive R 

Torilis nodosa (L.) Apiaceae Europa t unknown N R 

Trachycarpus fortunei (Hooker) Palmae Asia i subspontaneous N F 

Tragopogon crocifolius L. Asteraceae Mediterranean u adventive S 

Tribulus terrestris L. Zygophyllaceae Mediterranean t adventive R 

Trifolium alexandrinum L. Fabaceae Mediterranean t subspontaneous N R 

Trifolium hybridum L. Fabaceae Europa u naturalized N R 

Trifolium incarnatum L. Fabaceae Europa u subspontaneous N G 

Trifolium resupinatum L. Fabaceae Mediterranean u naturalized N R 

Trifolium suaveolens Willdenow Fabaceae Mediterranean t naturalized N R


Species Family Origin Life form Status Ecol. group 

Tulipa didieri Jordan Liliaceae Western Asia g unknown N R 

Tulipa grengiolensis Thommen Liliaceae Unknown g unknown N R 

Typha laxmannii Lepechin Typhaceae Eurasia g adventive H 

Ulex europaeus L. Fabaceae Europa n naturalized N F 

Ulmus laevis Pallas Ulmaceae Europa p subspontaneous C 

Vaccinium macrocarpon Aiton Ericaceae North America z naturalized N H 

Valerianella eriocarpa Desvaux Valerianaceae Mediterranean t adventive R 

Vallisneria spiralis L. Hydrocharitaceae Unknown a naturalized N E 

Veronica filiformis Smith Scrophulariaceae Eurasia h unknown N G 

Veronica peregrina L. Scrophulariaceae North America t unknown N R 

Veronica persica Poiret Scrophulariaceae Western Asia u unknown N R 

Vicia hybrida L. Fabaceae Europa u unknown N R 

Vicia lutea L. Fabaceae Mediterranean u adventive N R 

Vicia pannonica Crantz Fabaceae Europa u adventive N R 

Vicia peregrina L. Fabaceae Mediterranean t adventive R 

Vicia sativa L. Fabaceae Mediterranean u subspontaneous N R 

Vinca major L. Apocynaceae Eurasia z naturalized N M 

Viola obliqua Hill Violaceae North America g naturalized N F 

Vitis vinifera L. Vitaceae Europa p subspontaneous C 

Vulpia ciliata Dumortier Poaceae Mediterranean t adventive R 

Xanthium italicum Moretti Asteraceae North America t subspontaneous N G 

Xanthium spinosum L. Asteraceae South America t unknown N R 

Xeranthemum annuum L. Asteraceae Mediterranean t adventive R 

* Excluding cultivated plants which have not escaped in the environment 

Life form: p, deciduous tree; i, evergreen tree; n, deciduous shrub; j, evergreen shrub; z, woody chamaephytic plant (small shrub); c, herbaceous chamaephytic plant; hhemicryptophytic plant 

(perennial herb); g, geophytic plant (perennial herb with tubers, bulbs or rhizomes); t, annual plant; u, biennal plant; a, aquatic plant. 

Ecological group: R, ruderal plant; P, pioneer plant; F, forest plant; M, mountain plant; E, aquatic plant; H, marsh plant; S, dry meadow plant; G, meadow plant; C, cultivated plant; N, neophyte 

(according to Lauber and Wagner, 1998). 

Tab. 10.7 > Plant families with alien and naturalized species in Switzerland.* 

Family Taxonomy No. native 


No. alien 


No. naturalized 


Total no. 


% alien 


% naturalized 


% naturalized/ 

alien 

Aceraceae Dicot 4 1 0 5 20.0 0.0 0.0 

Agavaceae Monoc 0 1 1 1 100.0 100.0 100.0 

Aizoaceae Dicot 0 1 0 1 100.0 0.0 0.0 

Alismataceae Monoc 5 1 1 6 16.7 16.7 100.0 

Amarantaceae Dicot 0 9 0 9 100.0 0.0 0.0 

Amaryllidaceae Monoc 7 2 1 9 22.2 11.1 50.0 

Anacardiaceae Dicot 1 1 1 2 50.0 50.0 100.0 

Apiaceae Dicot 85 7 2 92 7.6 2.2 28.6 

Apocynaceae Dicot 1 1 1 2 50.0 50.0 100.0 

Araceae Monoc 3 3 2 6 50.0 33.3 66.7








Total no. 




% naturalized 




Asclepiadaceae Dicot 1 1 0 2 50.0 0.0 0.0 

Asteraceae Dicot 298 42 10 340 12.4 2.9 23.8 

Balsaminaceae Dicot 1 3 2 4 75.0 50.0 66.7 

Berberidaceae Dicot 1 2 1 3 66.7 33.3 50.0 

Bignoniaceae Dicot 0 1 0 1 100.0 0.0 0.0 

Boraginaceae Dicot 35 6 1 41 14.6 2.4 16.7 

Brassicaceae Dicot 129 35 7 164 21.3 4.3 20.0 

Buddlejaceae Dicot 0 1 1 1 100.0 100.0 100.0 

Cactaceae Dicot 0 2 0 2 100.0 0.0 0.0 

Campanulaceae Dicot 34 2 0 36 5.6 0.0 0.0 

Cannabaceae Dicot 1 1 0 2 50.0 0.0 0.0 

Caprifoliaceae Dicot 12 6 2 18 33.3 11.1 33.3 

Caryophyllaceae Dicot 117 6 1 123 4.9 0.8 16.7 

Chenopodiaceae Dicot 21 6 1 27 22.2 3.7 16.7 

Commelinaceae Monoc 0 1 1 1 100.0 100.0 100.0 

Cornaceae Dicot 2 1 1 3 33.3 33.3 100.0 

Crassulaceae Dicot 26 3 1 29 10.3 3.4 33.3 

Cupressaceae Gymnosperm 2 2 0 4 50.0 0.0 0.0 

Cuscutaceae Dicot 2 2 0 4 50.0 0.0 0.0 

Cyperaceae Monoc 131 4 2 135 3.0 1.5 50.0 

Dipsacaceae Dicot 15 2 1 17 11.8 5.9 50.0 

Droseraceae Dicot 4 1 0 5 20.0 0.0 0.0 

Elaeagnaceae Dicot 1 1 0 2 50.0 0.0 0.0 

Ericaceae Dicot 15 2 2 17 11.8 11.8 100.0 

Euphorbiaceae Dicot 17 8 1 25 32.0 4.0 12.5 

Fabaceae Dicot 135 25 6 160 15.6 3.8 24.0 

Fagaceae Dicot 7 1 1 8 12.5 12.5 100.0 

Fumariaceae Dicot 8 1 0 9 11.1 0.0 0.0 

Geraniaceae Dicot 20 4 0 24 16.7 0.0 0.0 

Hydrocharitaceae Monoc 1 6 5 7 85.7 71.4 83.3 

Hydrophyllaceae Dicot 0 1 0 1 100.0 0.0 0.0 

Hypericaceae Dicot 12 1 0 13 7.7 0.0 0.0 

Iridaceae Monoc 8 6 1 14 42.9 7.1 16.7 

Juncaceae Monoc 35 1 0 36 2.8 0.0 0.0 

Lamiaceae Dicot 82 4 2 86 4.7 2.3 50.0 

Lauraceae Dicot 0 1 1 1 100.0 100.0 100.0 

Lemnaceae Monoc 4 1 1 5 20.0 20.0 100.0 

Liliaceae Monoc 54 9 2 63 14.3 3.2 22.2 

Linaceae Dicot 4 2 1 6 33.3 16.7 50.0 

Malvaceae Dicot 4 4 0 8 50.0 0.0 0.0 

Mimosaceae Dicot 0 1 0 1 100.0 0.0 0.0 

Moraceae Dicot 1 1 0 2 50.0 0.0 0.0








Total no. 




% naturalized 




Oleaceae Dicot 3 2 0 5 40.0 0.0 0.0 

Onagraceae Dicot 21 5 1 26 19.2 3.8 20.0 

Oxalidaceae Dicot 2 1 0 3 33.3 0.0 0.0 

Palmae Monoc 0 1 0 1 100.0 0.0 0.0 

Papaveraceae Dicot 10 5 1 15 33.3 6.7 20.0 

Philadelphaceae Dicot 0 1 1 1 100.0 100.0 100.0 

Phytolaccaceae Dicot 0 2 2 2 100.0 100.0 100.0 

Pinaceae Gymnosperm 7 2 2 9 22.2 22.2 100.0 

Plantaginaceae Dicot 8 2 0 10 20.0 0.0 0.0 

Poaceae Monoc 189 31 5 220 14.1 2.3 16.1 

Polygonaceae Dicot 29 10 3 39 25.6 7.7 30.0 

Pontederiaceae Monoc 0 1 0 1 100.0 0.0 0.0 

Punicaceae Dicot 0 1 0 1 100.0 0.0 0.0 

Ranunculaceae Dicot 93 5 0 98 5.1 0.0 0.0 

Rosaceae Dicot 126 20 9 146 13.7 6.2 45.0 

Rubiaceae Dicot 34 3 1 37 8.1 2.7 33.3 

Salicaceae Dicot 33 1 0 34 2.9 0.0 0.0 

Sarraceniaceae Dicot 0 1 1 1 100.0 100.0 100.0 

Saxifragaceae Dicot 30 4 1 34 11.8 2.9 25.0 

Scrophulariaceae Dicot 106 12 5 118 10.2 4.2 41.7 

Simourabaceae Dicot 0 1 1 1 100.0 100.0 100.0 

Solanaceae Dicot 5 5 2 10 50.0 20.0 40.0 

Staphyleaceae Dicot 0 1 0 1 100.0 0.0 0.0 

Ulmaceae Dicot 3 1 0 4 25.0 0.0 0.0 

Valerianaceae Dicot 18 2 1 20 10.0 5.0 50.0 

Violaceae Dicot 25 1 1 26 3.8 3.8 100.0 

Vitaceae Dicot 0 3 1 3 100.0 33.3 33.3 

Zygopphyllaceae Dicot 0 1 0 1 100.0 0.0 0.0 

*Excluding cultivated plants which have not escaped into the environment 

Tab. 10.8 > Invasive plant species in Europe. 

Fact 

Sheet 

Species Ecol. Life 

group form 

Status CH 

1 

Austria 2 France 3 Spain 8 Portugal 

7 

Abutilon theophrasti Medik. R t adventive (econ.) x xx xx x 

yes Acer negundo L. F p subspont. xxx; 

(econ.) 

Scotland 

9 

Hungary 

5 

xxx x xxx 

Aesculus hippocastanum L. C p subspont. xxx 

Agave americana L. R j naturalized + M xxx xx 

yes Ailanthus altissima (Miller) P p naturalized xxx xxx xxx xxx xxx xxx xxx 

Allium paradoxum (M. v. Bieberstein) C g subspont. xx 

Amaranthus albus L. R t unknown x xxx 

Italy 6 Germany 4


Fact 

Sheet 


group form 

Status CH 

1 


7 

Scotland 

9 

Hungary 

5 

Italy 6 Germany 4 

Amaranthus blitum L. R t unknown x x 

Amaranthus cruentus L. R t subspont. xxx 

Amaranthus deflexus L. R u unknown x xxx xxx xxx 

Amaranthus retroflexus L. R t unknown econ. x xxx xxx xxx 

yes Ambrosia artemisiifolia L. R t adventive xxx xx; econ. xxx x x xxx xxx 

yes Amorpha fruticosa L. H n subspont. x xx ++ M xxx xxx 

Artemisia annua L. R t adventive x 

yes Artemisia verlotiorum Lamotte R g unknown xxx xxx x x xxx 

Arundo donax L. H g subspont. xxx xx 

yes Asclepias syriaca L. C R g subspont. xx + M xxx 

yes Aster lanceolatus Willdenow C g subspont. xxx ++ M xx xxx Aster spp. 

Aster novae-angliae L. H g subspont. 

yes Aster novi-belgii L. H c subspont. xxx xxx 

Aubrieta deltoidea (L.) S c naturalized 

Avena sativa L. C t subspont. x 

Bidens bipinnata L. R t naturalized xxx 

Bidens connata Willdenow H t naturalized +++ A 

yes Bidens frondosa L. R t naturalized xxx xxx xx xxx xxx 

Bidens subalternans DC. R t adventive xx 

Brassica napus L. C u subspont. x xx 

yes Buddleja davidii Franchet P n naturalized xxx xx xxx xxx xx 

yes Bunias orientalis L. R h unknown x ++ C xxx 

Cerastium tomentosum L. C c subspont. xx 

Chenopodium ambrosioides L. R t adventive +++ M x xxx 

Chrysanthemum Segetum L. R t unknown xx 

Cicerbita macrophylla (Willdenow) C g subspont. xx 

yes Conyza canadensis (L.) P u unknown +++ C xxx xxx xxx xxx xxx 

yes Cornus sericea L. F n naturalized x 

Coronopus didymus (L.) R u adventive x xxx 

Cotoneaster horizontalis Decne C j subspont. xx 

Crepis nemauensis Gouan R t naturalized 

Cymbalaria muralis P. Gaertn., B. Mey. & 

Scherb. 

P c unknown xx 

yes Cyperus eragrostis Lamarck H h unknown xxx xxx xx 

yes Cyperus esculentus L. H g unknown x xxx 

Cyperus rotundus L. H g naturalized 

Datura stramonium L. R t unknown x x xxx xxx xxx 

yes Duchesnea indica (Andrews) F h naturalized xx 

Eleusine indica (L.) R t naturalized xx x xxx 

yes Elodea canadensis Michaux E a unknown x xxx +++ C xxx xx xx xxx 

yes Elodea nuttallii (Planchon) E a naturalized xxx xx ++ C xx 

yes Epilobium ciliatum Rafinesque R h unknown xxx xxx x


Fact Species Ecol. Life Status CH Austria 

Sheet 

group form 

1 

2 France3 Spain8 Portugal7 

Scotland9 

Hungary5 

Italy6 Germany4 Erigeron annuus (L.) R u naturalized xx xxx xxx 

Erigeron karvinskianus DC. P h unknown + A xx 

Euphorbia maculata L. R t unknown x x 

Euphorbia prostrata Aiton R t adventive x 

Ficus carica L. C p subspont. x 

Galega officinalis L. G h subspont. ++ C 

yes Galinsoga ciliata (Rafinesque) R t unknown econ. x x xxx xxx 

yes Galinsoga parviflora Cavanilles R t unknown econ. x xx xxx xxx 

Gleditsia triacanthos L. C p subspont. xx 

Glyceria striata (Lamarck) H g unknown xx 

yes Helianthus tuberosus L. R g subspont. x xxx xxx xx xxx xxx xxx 

yes Heracleum mantegazzianum Sommier & 

Levier 

R h naturalized xxx xx; econ. xxx xxx xxx xxx 

yes Impatiens balfourii Hooker F. R t unknown + C 

yes Impatiens glandulifera Royle R t naturalized xxx xxx xxx xx xxx xxx xxx 

yes Impatiens parviflora DC. F t naturalized xxx xxx xxx 

Juncus tenuis Willdenow R h unknown ++ C 

Lagarosiphon major (Ridley) E a naturalized +++ A 

Lemna minuta Humboldt et al. E a naturalized xxx 

Lepidium virginicum L. R u unknown x x 

Ligustrum lucidum Aiton C i subspont. xx 

yes Lonicera henryi Hemsley F i subspont. x xx 

yes Lonicera japonica Thunberg F i naturalized xxx 

yes Ludwigia grandiflora (Michaux) E a naturalized xxx xxx 

yes Lupinus polyphyllus Lindley F h subspont. x xx 

Lycium barbarum L. C n subspont. ++ A 

Lysichiton americanus Hultén & H. St. John H g naturalized xxx 

Lysimachia punctata L. C H h subspont. xx 

yes Mahonia aquifolium (Pursh) F R j subspont. x xx 

Matricaria discoidea DC. R t unknown + C xx xxx 

Meconopsis cambrica (L.) R h unknown xx 

Medicago sativa L. C h subspont. x 

Mimulus guttatus DC. H g naturalized xx 

Morus alba L. C p subspont. ++ C 

Nicandra physalodes (L.) C R t subspont. xxx 

yes Oenothera biennis L. R u unknown xxx x x xxx 

Oenothera glazioviana Micheli R u unknown x x 

Opuntia imbricata (Haworth) S c unknown xxx 

Oxalis fontana Bunge R u unknown x 

Panicum capillare L. R t naturalized x x 

Panicum dichotomiflorum Michaux R t naturalized x xxx 

Parthenocissus quinquefolia (L.) F p naturalized


Fact 

Sheet 


group form 

Parthenocissus tricuspidata (Siebold et 

Zuccarini) 

Status CH 

1 


7 

Scotland 

9 

Hungary 

5 

Italy 6 Germany 4 

C p subspont. xx xxx Parthen. spp. 

yes Paspalum dilatatum Poiret H g adventive xxx xxx xxx 

Paulownia tomentosa (Thunberg) F p subspont. 

Phalaris canariensis L. R t adventive x 

yes Phytolacca americana L. R h naturalized x xx xxx xxx 

Phytolacca esculenta Van Houtte R h naturalized 

Polygonum orientale L. R t subspont. x 

yes Polygonum polystachyum Meissner R g naturalized xxx 

yes Prunus laurocerasus L. F i naturalized x xx 

yes Prunus serotina Ehrhart F p naturalized xxx xx xxx 

Pseudotsuga menziesii (Mirbel) F i naturalized xx 

yes Pueraria lobata (Willdenow) F R p subspont. x 

yes Reynoutria japonica Houttuyn R g naturalized xxx xxx; 

econ. 

yes Reynoutria sachalinensis (F. Schmidt) R g subspont. xxx xx; 

(econ.) 

yes Rhus typhina L. P p naturalized xxx 

xxx xxx x xxx xxx xxx 

xxx xx xxx xxx 

Ribes rubrum L. C n subspont. x 

yes Robinia pseudoacacia L. F p naturalized xxx xxx; 

econ. 

Rorippa austriaca (Crantz) H h adventive + C 

xxx xxx xx xxx xxx 

yes Rosa rugosa Thunberg R n subspont. xxx 

Rubia tinctorum L. R h naturalized x 

yes Rubus armeniacus Focke F n naturalized xxx 

Rudbeckia hirta L. C u subspont. xxx 

yes Rudbeckia laciniata L. C g subspont. xxx xxx 

Rumex longifolius DC. P h unknown 

Rumex patientia L. C R h subspont. + C 

Rumex thyrsiflorus Fingerhuth R h unknown ++ C 

Rumex confertus Willdenow P h naturalized 

Sedum spurium M. Bieberstein R c subspont. x 

Sedum hispanicum L. P u unknown 

yes Senecio inaequidens DC. R u naturalized xxx x xxx xxx xxx 

Senecio rupestris Waldstein et Kitaibel R u unknown x 

Solanum sublobatum Roemer et Schultes R t naturalized ++ M 

yes Solidago canadensis L. R g naturalized xxx xxx +++ C xxx xxx 

yes Solidago gigantea Aiton H g naturalized xxx xxx; 

(econ) 

Sorghum halepense (L.) R h unknown x xx x 

+++ C x xxx xxx xxx 

Symphoricarpos albus (L.) F n naturalized xxx 

Symphytum asperum Lepechin R h naturalized +++ C xx 

Syringa vulgaris L. C n subspont. xx


Fact 

Sheet 


group form 

Status CH 

1 


7 

Tanacetum parthenium (L.) C h subspont. xx 

Tetragonia tetragonioides (Pallas) C t subspont. ++ M x 

Trachycarpus fortunei (Hooker) F i subspont. x 

Trifolium incarnatum L. G u subspont. x 

Trifolium resupinatum L. R u naturalized x 

Ulex europaeus L. F n naturalized ++ A 

Vaccinium macrocarpon Aiton H z naturalized 

Veronica filiformis Smith G h unknown xx 

Veronica peregrina L. R t unknown + C x 

Veronica persica Poiret R u unknown xx xxx xx 

Xanthium spinosum L. R t unknown + M xx xx 

xxx, invasive species (black list); xx, potentially or moderately invasive species; species in expansion, locally invasive; x, species present; need to be followed up (watch list). 

+++ – For France: invasive species in one sector only: M (Mediterranean area); A (Atlantic area); C (continental area); 

++ – For France: potentially invasive in one sector only: M, A or C; 

+ – For France: species present, which need to be followed up (Watch List), in one sector only: M, A or C. 

1 Switzerland: - CPS-SKEW (http://www.cps-skew.ch/) 

2 Austria: Essl, F. and W. Rabitsch (eds) (2002) Neobiota in Österreich. Federal Environment Agency, 432 pp. 

3 France: Muller, S. (2004) Plantes invasives en France. Paris, Muséum National d’Histoire Naturelle. Patrimoines naturels; 62, 176 pp. 

4 Germany: From a preliminary EPPO list of invasive alien plants for the EPPO region (plants from Germany include mostly species in the category xxx) 

5 Hungary: Invasive alien species in Hungary. National Ecological Network No. 6 (the list includes only invasive plant species in Hungarian protected areas) 

6 Italy: Laura Celesti, pers. comm. (2003). The species given for Italy are those most frequent in northern Italy 

7 Portugal: De Almeida, J.D. (1999) Flora exotica subespontanea de Portugal continental. Universidade de Coimbra, 151 pp. 

8 Spain: Dana, E.D., Sanz-Elorza, M. & E. Sobrino (2001) Plant invaders in Spain, http://www.ual.es/personal/edana/alienplants/checklist.pdf 

9 Scotland: Welch, D. et al., (2001) An audit of alien species in Scotland. Scottish Natural Heritage Review No 139, 225 pp. 

> Fact sheets 

The fact sheets are available at http://www.environment-switzerland.ch/uw-0629-e. 

Scotland 

9 

Hungary 

5 

Italy 6 Germany 4

Invasive alien species in Switzerland - Schweizer ...

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