Volume 10 Numbers 2 & 3 2009 SPECIAL

knowledge - conservation - sustainability

Journal of life on earth

INVASIVE ALIEN SPECIES

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introductioninvasive alien species (iAs) cause major economic losses and ecosystem damage worldwide. in the UsA alone introduced insect pests cost agriculture about $13.5 billion per year and forestry about $2.1 billion (Pimentel et al. 2005). iAs were identified as the primary cause for endangerment for about half of all endangered species in UsA (wilcove et al. 1998). Recent increases in world trade increase the likelihood of new iAs introductions and effective quarantine actions against them require strong taxonomic knowledge of native and exotic biota (lyal et al. 2008). Taxonomic information is essential for initiating defence against iAs by providing rapid, accurate identification of IAS new to an area. Taxonomy is integral to all stages of iAs response including prevention of new invasions, early detection of and rapid response to new invaders and management of established invaders. Once invaders arrive and are detected and identified, further taxonomic research is usually needed for short and long term response. Here, research on ecological interactions among the pest, host and ecosystem are all indispensable in planning initial defensive strategies and integrated control measures such as biological control.

“Taxonomy is an information science responsible for erecting formal classifications and maintaining names that make possible the storage, retrieval, organization and communication of billions of facts about millions of species” (wheeler 2009). This practical statement was part of his two part definition of taxonomy (the other part treated the underlying evolutionary theories and the taxonomic conventions). since linnaeus, 250 years of taxonomic research have provided a large knowledge base about the diversity of living organisms from which useful, accurate predictions can be made about the possible origins of various iAs.

The most important role of taxonomists is to produce the names, descriptions and keys to taxa and the predictive classifications that enable inference about IAS. This primary taxonomic literature, and the secondary biological and ecological literature, based on the names occurring in the primary literature and authoritative identifications by competent taxonomists, are the primary benefits of taxonomy. Taxonomic revisions, catalogues and checklists of various taxa for particular regions or the world provide a species diversity baseline from which predictions about iAs can be made. The primary taxonomy literature, which tests taxonomic and phylogenetic hypotheses using morphological, molecular sequence and other biological and ecological data is scattered in thousands of publications worldwide. DnA barcode data represent a powerful new tool for species hypothesis testing, but sound scientific conclusions require taxonomic investigation involving multiple evidence sources (e.g. schmidt and sperling 2008). More comprehensive, synthetic works such as generic revisions containing illustrated identification keys for countries, biogeographical regions or, even the world, are required, but fewer are produced because of the time required to gather and synthesize the specimens and information for study. These primary sources provide information for all secondary taxonomic works, such as catalogues, checklists, distribution maps and, eventually (as tertiary works), taxonomic or biological treatments of species or genera that affect humans, ecosystems or particular commodities e.g., wheat or cattle.

such taxonomic tools and research capability are essential to all stages of iAs response. This includes not only initial detection and identification of IAS, but also response and control, which requires understanding the ecology of invaders in their native and introduced ranges. such understanding is needed to determine whether and how control measures should be initiated. Possible responses include localized intensive eradication efforts, quarantine measures and biological control. Here we provide examples of how taxonomy has contributed to preventing, detecting or correcting short and long term response to outbreaks of Gastropoda (snails) and lepidoptera, Diptera, Coleoptera and Hymenoptera. Further, we show how

The importance of taxonomy in responses to invasive alien speciesH. Douglas1, P.T. Dang2, B.D. Gill1, J. Huber3, P.G. Mason2, D.J. Parker1, B.J. Sinclair1.

authors’ addresses: 1 entomology, Ottawa Plant & seed laboratories, Canadian Food inspection Agency, Bldg. 18, 960 Carling Ave., Ottawa, Ontario, K1A 0C6, Canada

2 Agriculture and Agri-Food Canada, Research Centre, K.w. neatby Building, 960 Carling Ave., Ottawa, On, K1A 0C6, CAnADA

3 Canadian Forest service, natural Resources Canada, c/o AAFC Research Centre, K.w. neatby Building, 960 Carling Ave., Ottawa, On, K1A 0C6, Canada

Abstract. Invasive alien species (IAS) cause major economic losses and threaten biodiversity worldwide. Taxonomic information is essential to initiating defence against IAS, including early detection and identification of new IAS outbreaks. We demonstrate how current IAS strategies (i.e. prevention of new invasions, early detection and rapid response to new invaders and management of established invaders) require strong taxonomic infrastructure. Examples are given from terrestrial molluscs (Gastropoda) and insects such as the Gypsy Moth, Lymantria dispar Linnaeus (Lepidoptera: Lymantriidae), disease vector flies of the families Culicidae and Calliphoridae (Diptera:), Sirex noctilio (Fabricius) (Hymenoptera: Siricidae) woodwasps and Dendroctonus bark beetles and the cabbage seedpod weevil, Ceutorhynchus obstrictus (Marsham) (Coleoptera: Curculionidae), that demonstrate the role of taxonomy in IAS response. Further, we show through the example of the Emerald Ash Borer, Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), how international co-operation is essential to identify initial outbreaks of IAS. Such international co-operation is especially important because few countries can fund comprehensive pest identification organizations alone.

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international co-operation was essential to initially identify the emerald Ash Borer beetle, Agrilus planipennis Fairmaire (Coleoptera: Buprestidae). such international co-operation is especially important because all insect collections have limited content, few countries can fund comprehensive pest identification organizations, and even in those countries the number of taxonomists is declining (Haas and Häuser 2005; Grant 2009).

Taxonomic names of accurately defined species are necessary to access all published information on species and when combined with biological information allow further syntheses that provide others, including quarantine officials, decision makers and non-taxonomists, with needed information about invasive species. examples of such synthetic works for iAs in forests are: Hendrickson (2002) for Canada, Moore (2005) and FAO (2009) for the world. From a forestry perspective, the examples below show the importance of taxonomy in determining what iAs are and what groups are likely to cause future problems. what taxonomy cannot usually do is predict specific details, such as which particular species will become iAs, and where and when that might happen. However, Pest Risk Assessments (PRA) based on sound taxonomy can often predict which species are likely to be invasive pests once introduced beyond their native ranges. such PRAs are part of the information that regulatory organizations use to make decisions about which import

commodities to allow, and from where. with a comprehensive set of sound PRAs, countries would be better able to protect themselves against imports of commodities infested with iAs.

BiologicAl control from A forestry perspectiveOne further point is that iAs would be more common and destructive without the insect and spider predators or parasitoids (especially Hymenoptera and Diptera) that control them. Hymenoptera, in particular, can be specific and useful in biological control, but implementation is hampered by a lack of taxonomic knowledge (Grissell 1999; Huber 2009). The taxonomy of predators and parasitoid groups is as important as that of groups containing potential iAs.

Classical biological control (moving natural enemies to new areas where they do not occur) has been extremely important for controlling IAS in forests. Many exotic sawflies and wood wasps (Hymenoptera: symphyta) have been reduced to minor or insignificant pest status by introduced parasitoids (e.g., ichneumon or chalcid wasps) or pathogens (e.g. nematodes, viruses), as shown by examples from Canada (McGugan and Coppel 1962; langor et al. 2002) and new Zealand (nuttall 1989). However, before biological control agents are deliberately introduced into a new area they need to be correctly identified, necessitating collaboration with taxonomists. Taxonomists, in turn, may obtain useful biological information from biological

Gypsy Moth, Lymantria dispar l.,Male, female and caterpillar (Courtesy of nRCan).

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control workers helping them resolve taxonomic problems, especially distinguishing cryptic species (Huber et al. 2001).

gypsy mothLymantria dispar linnaeus (lepidoptera: lymantriidae) is an important invasive pest in eastern north American deciduous forests, and was considered by lowe et al. (2004) to be among the 100 most invasive species worldwide. Ferguson (1978) revised the 46 north American species of lymantriidae. He reported 30% as pests, possibly the highest percentage for any group of insects, and found that all species in the tribe lymantriini in the nearctic region were introduced from the Palearctic region. in contrast, he estimated that Afro-eurasia has as many as 150 native Lymantria Hübner (lymantriini) species. Pogue and schaefer (2007) taxonomically treated 31 species of Lymantria from Asia, where the genus is most diverse, and considered all potentially invasive.

Despite there being no native Lymantria in the nearctic region, 26 species of native nearctic parasitoids and 17 insect predators have been found feeding on Gypsy Moth (Griffiths and Quednau 1984), complementing the effects of nine parasitoid species introduced from europe. Gypsy Moth is also attacked by a bacterium, Bacillus thuringiensis Berliner serovar kurstaki (Bacillaceae), two introduced pathogens: a virus, nuclear polyhedrosis virus and a fungus, Entomophaga maimaiga Humber, shimazu and soper (Zygomycetes: entomophthoraceae). All agents, whether native or introduced, initially required identification and description by taxonomists. The effects of the introduced parasitoids and pathogens on native biodiversity are largely unknown but examples of negative effects have been found. At least one parasitic fly, Compsilura concinnata (Meigen) (Diptera: Tachinidae), introduced from europe to control the Browntail Moth, Euproctis chrysorrhoea linnaeus (lepidoptera: lymantriidae), has a wide host range and has been blamed for reducing numbers of non-target hosts including native north American saturniidae (lepidoptera) (Boettner et al. 2000; Kellog et al. 2003). in this case releasing biological control organisms without sufficient knowledge of the biological characteristics and potential of the parasitoid species damaged native biodiversity.

bark beetles (coleoptera: curculionidae: scolytinae)There are 19 species of Dendroctonus erichson (Coleoptera: Curculionidae) bark beetles in the nearctic region and only 2 native to the Palaearctic. Dendroctonus species include major forest pests, as shown by the over 50 pages of literature references in the world catalog of scolytinae (wood and Bright 1992 and supplements up to 1999). several are potential iAs, and D. valens leConte (the Red Turpentine Beetle) is already an iAs in China, introduced accidentally in the 1980’s from north America. Governments in eurasia and north Africa clearly need to prevent Dendroctonus or other scolytinae (e.g., Ips DeGeer species) from entering and establishing in their countries. Comprehensive taxonomic and bibliographic compilations on scolytinae by two taxonomists, s.l. wood and D. e. Bright, Jr., have made scolytinae well-

known taxonomically, thus providing an easily accessible information source on their systematics, hosts and biology. in contrast, almost nothing has been done with biological control using parasitoids, the emphasis being placed instead on competitors, predators and pathogens (safranyik et al. 2002). Research on biological control organisms could reduce the risk that these Dendroctonus species pose.

wood wasps The family siricidae (Hymenoptera), commonly called woodwasps, occurs only in the northern Hemisphere except for one genus in central Africa. Sirex noctilio (Fabricius) is a pest of pine trees (Pinus spp.) that is native to the Palearctic region. several species of introduced pines grown in the southern Hemisphere are thus at risk to any Sirex spp. introduced from the northern Hemisphere. Sirex noctilio destroyed Pinus radiata plantations in new Zealand and elsewhere until biocontrol agents were discovered and introduced. Five of the ten biological Hymenoptera control agents established and spread, effectively reducing populations of S. noctilio to low levels (nuttall 1989). A nematode was also found but arrived naturally inside its Sirex host instead of being deliberately introduced. All the parasitic wasp biocontrol agents obviously had to be accurately identified by taxonomists before being released in new Zealand. north America is the latest region into which S. noctilio was accidentally introduced. in response, a taxonomist is now revising the species of the entire family siricidae for the new world, so that this or any other alien siricid species can be distinguished from all the native ones.

From a conservation perspective, Pinus species are exotic to the southern hemisphere, so the establishment of pine plantations there initially increased biodiversity but may also have decreased it by displacing native species. Thus, an unintentionally introduced pest of the introduced pines could be seen as a beneficial agent favouring native plant species by reducing the deliberately introduced species considered useful to humans. intentional introduction of biological control agents of S. noctilio ultimately re-established the desired situation from a forest resource perspective, i.e., the continued presence of exotic pines in plantations in the southern Hemisphere. Depending on one’s viewpoint any of the introduced species could be viewed as deleterious or beneficial to the biodiversity of an area. In the New Zealand example, the introduced biocontrol agents of S. noctilio are perceived by most as beneficial to humans, regardless of their effect in maintaining intentionally introduced alien species that may reduce the native biodiversity of the country.

it is preferable that taxonomic syntheses of genera containing potential iAs precede introductions, but such syntheses may be initiated in response to an iAs arriving in a new region, as is being done for Sirex in north America. Regardless, it is clear that the ability of quarantine officers to recognize actual or potential iAs is seriously compromised without taxonomic work to provide the necessary background knowledge in a useful form, e.g., identification keys, catalogues.

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BiologicAl control from An Agriculture perspectiveTaxonomy plays a key role in biological control of agricultural pests. The example of Cabbage seedpod weevil, Ceutorhynchus obstrictus (Marsham) (Coleoptera: Curculionidae), in Canada illustrates how sound taxonomic research can explain perceived failure, clarify taxonomic names and enhance understanding of biodiversity. This invasive alien species, native to Europe, was first recorded in north America in 1931 at the port city of Vancouver (Mcleod 1962), and has since spread to other parts of western and eastern north America (Baker 1936; Hagen 1946; Crowell 1952; walz 1957; Anonymous 1977; Dolinski 1979; Boyd and lentz 1994; Buntin et al. 1995; Cárcamo et al. 2001; Dosdall et al. 2002; Brodeur et al. 2001; Mason et al. 2004). The cabbage seedpod weevil is a serious pest of canola and rapeseed (Brassica napus l. and Brassica rapa l.) (Brassicaceae) in north America (McCaffrey 1992; Buntin et al. 1995; Cárcamo et al. 2001; Dosdall et al. 2002; Kuhlmann et al. 2002; Mason et al. 2004), dispersing at a rate of approximately 55 km per year (Dosdall et al. 2002) and it is expected to eventually spread throughout the entire canola-growing region of western Canada. Under climate change scenarios, it is predicted that an average temperature increase of 3oC would result in the expansion of the range of C. obstrictus into the northern areas of the Canadian prairies (Olfert and weiss 2006).

soon after Cabbage seedpod weevil was discovered, several parasitoids (Hymenoptera: Chalcidoidea) were reared from this host and identified as various taxa, including the European species Trichomalus perfectus (walker) and Mesopolobus morys (walker) (Pteromalidae). These parasitoid species were thought to have been introduced accidentally along with the pest (see review by Gibson et al. 2005). A classical biological control release against Cabbage seedpod weevil was also made in 1949 in British Columbia with the release of three species of Pteromalidae (Hymenoptera) that were then identified as Trichomalus fasciatus (Thompson) [= Trichomalus lucidus (walker)], Xenocrepis pura Mayr [= Mesopolobus morys (walker)] and Habrocytus sp. (Mcleod 1962).

The weevil’s invasion of the canola growing regions of Alberta, saskatchewan, Ontario and Quebec in the late 1990’s led to new surveys to identify the parasitoids present, what their impact on Cabbage seedpod weevil was, and whether the introduction of additional parasitoids from europe would be warranted. in particular, the apparent ineffectiveness of T. perfectus as a biological control agent of the Cabbage seedpod weevil in north America, although it is highly effective in europe (typically occurring at infection prevalence levels >50% and up to 90%) indicated the need for taxonomic examination of the parasitoid complex associated with the Cabbage seedpod weevil. Resulting taxonomic study of voucher specimens of the three species introduced into British Columbia in 1949 revealed that the species introduced as T. fasciatus was actually Trichomalus perfectus (walker)

and the Habrocytus sp. was Stenomalina gracilis (walker), but new surveys determined that of the three species only S. gracilis had established (Gibson et al. 2006b). Furthermore, more extensive taxonomic review of the parasitoids associated with Cabbage seedpod weevil in north America revealed that most species had been misidentified and included several species not previously known to be associated with Cabbage seedpod weevil (Gibson et al. 2005, 2006a & b). it was determined that all previous identifications of T. perfectus in North America were misidentifications of T. lucidus and those of M. morys were misidentifications of an undescribed species, subsequently described as M. moryoides Gibson (Gibson et al. 2005). Collaborative taxonomic research also resulted in description of a new parasitoid species associated with cabbage seedpod weevil in north America (Gibson et al. 2005), development of new keys for the identification of Trichomalus Thomson spp. (Muller et al. 2007) and Mesopolobus westwood spp. (Bauer et al. 2007) associated with Ceutorhynchus species of european origin, and an illustrated key to the parasitoids of the cabbage seedpod weevil in north America (Gibson et al. 2006b). Furthermore, new parasitoid-host associations were determined (Gibson et al. 2005; Gillespie et al. 2006; Bauer et al. 2007; Dosdall et al. 2007; Muller et al. 2007; Mason et al. unpublished).

Parasitism levels of the Cabbage seedpod weevil remain low (<10%) even in British Columbia where the pest has been present since the 1930’s. Furthermore, abundance of the parasitoid species varies from region to region. it is clear that native parasitoids have not adapted and are unlikely to adapt to Cabbage seedpod weevil and regulate pest populations. Thus, importation of parasitoid species important in regulating Cabbage seedpod weevil in the area of origin, such as T. perfectus or M. morys, remains the best option to control Cabbage seedpod weevil. However, native north American parasitoid species that attack this invasive alien species threaten native Ceutorhynchus weevils that may also be hosts. High populations of Cabbage seedpod weevil would provide a resource that would enable increases in numbers of native parasitoids that could increase mortality of native Ceutorhynchus weevils, a parasitoid spillback (see Kelly et al. 2009).

in clarifying the status of the parasitoid complex associated with Cabbage seedpod weevil, taxonomy played a critical role in establishing the actual species that parasitize this pest in North America, The correction of the parasitoid identifications was made possible because of improved taxonomy of the taxa in europe in the 1960’s (particularly Graham’s 1969 revision of Pteromalidae of northwestern europe) and deposition of authoritatively identified specimens of European species in the CnC which were then available for comparison. Furthermore, this example demonstrates that initial identifications of IAS pest/parasitoids are often misidentifications because of the immediate lack of taxonomic knowledge or comparative specimens. Therefore, initial identifications of the pest and biological control agents should be reviewed as taxonomic knowledge improves in both the area of origin and the

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region of introduction. The most recent taxonomic work also corrected the assumption that introduced european species of parasitoids had failed for biological control of cabbage seedpod weevil. Finally, our understanding of the diversity of parasitoids associated with ceutorhynchine weevils in north America was improved.

Agrilus plAnipennis And the necessity for internAtionAl cooperAtion in tAxonomyinvasive alien species pose a special challenge to taxonomists and quarantine services because they can suddenly appear in port or industrial areas with no indication of their origins. The first hurdle is to decide if the specimen represents an undescribed native species, which can be a challenge, or if it is a described exotic species (a bigger challenge), or perhaps an undescribed exotic species (the biggest challenge). Most identification specialists are familiar with their local and regional faunas, or with a modest range of taxa on a global basis. when an unknown species arrives from an unknown area, identifiers are unlikely to be able to make an accurate identification due to a lack of appropriate literature and voucher specimens. The free exchange of information and specimens among international experts is critical for the rapid and accurate identification of new IAS.

The discovery of Agrilus planipennis or the emerald Ash Borer (eAB) as it is called in north America is a good example that highlights the importance of international cooperation among taxonomists in the battle against invasive alien species. eAB was first reared in North America from dying ash trees in the Detroit area of Michigan in May and June of 2002 (Haack et al. 2002; Cappaert et al. 2005). specimens were initially identified as an Agrilus species by an entomologist at Michigan state University who suspected that it might be exotic because it did not resemble any native species. samples were sent to the United states Department of Agriculture and to leading buprestid taxonomists in the U.S. for further identification. A consensus emerged that it was likely an Asian Agrilus, but with no voucher specimens in north American collections it was not possible to determine the actual species. An email with digital images was subsequently sent by Richard westcott (Oregon Department of Agriculture) to eduard Jendek (slovak Academy of sciences, Bratislava) who had been working on Asian Agrilus species for many years. Jendek made a tentative identification of A. planipennis based on the email, which he confirmed once he received pinned specimens by mail (Haack et al. 2002). After the Michigan specimens were identified, beetles from neighbouring windsor, Ontario, submitted to the Canadian Food inspection Agency were forwarded to Westcott who confirmed the presence of this pest in Canada.

The identity of this new iAs was solved by Jendek who had previously been able to study the type specimen of A. planipennis in the Muséum national d’Histoire naturelle in Paris and had published on it (Jendek 1994). The accurate identification of EAB in the U.S. and Canada required the collaboration of international experts and the ability to send

preserved voucher specimens quickly and efficiently across several international borders. Once this pest had been identified, the published literature could be reviewed to summarize the known distribution and biology (wei et al. 2004) and research could begin to address additional questions on the biology and to search for potential biological control agents (liu et al. 2003; Bauer et al. 2008). Unfortunately, the rise of national and international regulations that prevents the free exchange or shipment of material among taxonomists threatens to undermine such cooperation, which imperils the flora and fauna that many of these regulations were designed to protect. if Jendek had not resided in Slovakia, the identification of EAB could have been problematic. while north Americans were struggling to identify eAB in 2002, at least one south Asian government was busy passing a Biological Diversity Act in response to the United nations Convention on Biological Diversity (CBD). The aim of the CBD is to protect the genetic resources of sovereign nations and to prevent the commercial exploitation of native flora and fauna. While biological diversity acts are valuable tools to protect wildlife and reduce biopiracy, they can prevent the legitimate exchange of specimens across borders, penalizing both domestic and foreign scientists alike (Prathapan et al. 2006, 2008). Canada and UsA are not immune, as Canadian scientists, trying to ship dead insects to colleagues in the U.s. for identification, have had shipments stopped and been notified by the U.s. Fish and wildlife service that the genus and species names for all specimens must be listed for the shipment to be delivered. if this basic information was known, there would have been no reason to ship the specimens in the first place. In Canada, the wild Animal and Plant Protection and Regulation of international and interprovincial Act (wAPPRiiTA) makes it an offence to violate any foreign law related to wildlife. For those countries that declare all species of flora and fauna protected, possession of any specimens, including dead fruit flies or cockroaches, becomes an offence. The implementation of these well intentioned laws needs to be tempered with the realization that the free exchange of voucher specimens among taxonomists is critical in protecting native flora and fauna from invasive alien species.

tAxonomy And terrestriAl mollusc pests (gAstropodA) in cAnAdAMolluscs are the second largest animal phylum on earth after the arthropods. The terrestrial snails and slugs of Canada (land snails hereafter) are poorly known. There have been few faunistic surveys of land snails across Canada and there are probably many undescribed native species. Of the 200 species known to occur in Canada about 50 remain undescribed. Also, 10–25% of Canada’s fauna are exotic species (Forsyth 2009, personal communication). in British Columbia, almost one-third of all land snail species are exotic (Forsyth 2004). The biggest barrier to responding to these exotic species in Canada is that there are no terrestrial malacologists in Canadian federal or provincial laboratories. The Canadian Food inspection Agency, who regulate land snail imports and gastropods as plant pests, often seek assistance outside their own diagnostic

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service for mollusc interceptions. Canada has terrestrial mollusc collections at the Canadian Museum of nature (Ottawa), The Royal British Columbia Museum (Victoria), the Royal Ontario Museum (Toronto) and several smaller museums. Because of its poorly known fauna, the lack of taxonomic researchers, outdated literature, small collections and increasing global trade, Canada is vulnerable to new introductions of exotic terrestrial molluscs. However, recently there have been several promising developments in diagnostic keys for terrestrial molluscs. The Canadian Food inspection Agency is funding a field-guide to the native and introduced molluscs of eastern Canada (to be published in 2009). There is also a recent publication on the land snails of British Columbia (Forsyth 2004). These guides allow genus or species level identification of most established and commonly intercepted land snail pests, but without taxonomic support how can Canada protect itself against invasive exotic snails and slugs?

Many terrestrial snails and slugs damage agriculture and forestry, the environment and human health (Forsyth 2004). snails are known vectors of serious animal pathogens. without curated collections, faunistic surveys, libraries, taxonomists and identifiers, Canada will be unaware of new introductions and will only be capable of reaction to invasive species long after establishment. The CFiA regularly intercepts many non-indigenous snails but there is a limit to the effectiveness of quarantine when so little is known of the Canadian fauna and those of its trading partners. Governments and universities would benefit from collaborating to support taxonomic research in terrestrial malacology. The resulting survey of the terrestrial land snail biodiversity of Canada would make this country better prepared for new invasive introductions. Here, as elsewhere, detection of biological invasions requires a comprehensive literature and personnel who are able to use it.

tAxonomy And invAsive Alien dipterANumerous invasive flies (Diptera) in the families Agromyzidae, Anthomyiidae, Calliphoridae, Culicidae, Drosophilidae, Muscidae, Phoridae, Psilidae, sarcophagidae and Tephritidae are known, but our attention is mostly focussed toward pests and disease vectors. Detailed studies of the devastating effects of introduced vector mosquitoes and the diseases they transmit have been well documented (lounibos 2002). in addition, there have been extensive investigations into the taxonomic genetic structure of disease vector mosquitoes (Collins & Paskewitz 1996; Krzywinski & Besansky 2003; scheffer 2005). The interspecific displacement effect of invasive dipterans on local species has been studied for blow flies (Calliphoridae) (Baumgartner & Greenberg 1984; wells & Greenberg 1992) and mosquitoes (Culicidae) (Juliano & lounibos 2005). The impact of introduced flies upon non-insect faunas has also attracted much recent attention. The endangerment and extinction of native species of Hawaiian birds with the introduction of avian malaria and a suitable vector, Culex quinquefasciatus say (Culicidae), has been documented (van Riper et al. 1986). in the Galápagos islands the introduction of the nestling parasite Philornis downsi Dodge & Aitken (Muscidae) is considered

a serious threat to the endemic passerine fauna (Fessl et al. 2006; wiedenfeld et al. 2007). Traditional taxonomy played a key role in determining that P. downsi was not native to the islands and that it comprised a single invasive species (sinclair unpublished data), which has been verified in recent genetic studies of this parasitic fly (Dudaniec et al. 2008).

conclusionsAs demonstrated in the above examples, taxonomy is required at all stages of interaction with iAs insect and terrestrial mollusc pests. without adequate taxonomic infrastructure, detections and accurate identifications are delayed or not possible, resulting in delayed or misguided responses and controls. ideally, the systematics of pest groups and their natural agents of biological control should be well understood before introduction, whether accidental or intentional, as we demonstrate above. This is essential for timely detection, identification and management of iAs. such studies should include ‘rare pests’ that do not normally cause measurable damage in their native ranges. This is because invasive species often have novel ecological characteristics or lack the parasitoids, predators and other control agents in their introduced range that naturally suppress their populations in their area of origin. efforts to understand insect faunas in this detail are only practicable through international collaboration among scientists. exchange of specimens for study could be facilitated by minor amendments to the existing laws and regulations of various national governments.

in the absence of robust taxonomies of pest groups, good taxonomic research capacity is essential to iAs response. specimen collections, libraries and laboratories staffed with qualified scientists, identifiers and technicians allow both provisional specimen identification even without a complete literature and the capacity to conduct taxonomic research. This research should be both proactive, to prepare for expected biological invasions, and emergency-based, in response to recent invasions or interceptions. The examples discussed above demonstrate the need for continued taxonomic work in response to ongoing invasions and the costs of implementing biological control without sufficient involvement of taxonomic researchers.

AcKnowledgmentswe thank M. Damus, G. Gibson and an anonymous reviewer for their helpful comments.

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