Invasive Species Specialist Group Research Articles

Table S1. Basic background information of plant species considered invasive based on the Invasive Species Specialist Group of IUCN (www.issg.org). The most harmful invasive plant species are marked with a red background color.

Table S1. Basic background information of plant species considered invasive based on the Invasive Species Specialist Group of IUCN (www.issg.org). The most harmful invasive plant species are marked with a red background color.

Results of Survey and Evaluation of Invasive Plants in Ba Vi National Park, Vietnam

The biodiversity of Ba Vi National Park has been faced with some passive impacts, one of them is alien species, that habitats for the native species is narrowed by increasing of invasive population expanding, it is necessary to conducted a research on the impacts of the invasive plants there and then giving the basis for better management of the national park. After field surveys in recently years (2018-2022), 47 alliance species recorded at the National Park were evaluated according to guidance and data provided by Invasive Species Specialist Group (ISSG) and Centre for Agriculture and Biosciences International (CABI) developed Invasive Species Compendium (ISC) and also Circular 35/2018/TT-BTNMT. Result showed that 29 species were invaders and especially 11 species of them are detailly evaluated in 10 habitats. 2 species as Mexican sunflower (Tithonia diversifolia) and Lantana (Lantana camara) are evaluated as High risk for both areas while 3 other ones are evaluated as High risk for buffer zone only, including Giant sensitive tree), Leucaena (Leucaena leucocephala) and Giant sensitive plant (Mimosa diplotricha). The other ones have been evaluated as Medium risk (at buffer zone) to Low risk (at core area) are Blackjack (Bidens pilosa), Siam weed (Chromolaena odorata), Bay Biscayne creeping-oxeye (Sphagneticola trilobata), Jamaica cherry (Muntingia calabura), Jamaica vervain (Stachytarpheta jamaicensis) and Coast morning glory (Ipomoea cairica). By this evaluation, Mexican sunflower (Tithonia diversifolia), Blackjack (Bidens pilosa), Jamaica cherry (Muntingia calabura), Jamaica vervain (Stachytarpheta jamaicensis) and Coast morning glory (Ipomoea cairica) are suggested to include to the list of invasive organisms of the nation. Besides that, it is necessary to strengthen control of Mexican sunflower (Tithonia diversifolia) inside the core area of the NP in particular and in Ba Vi district in general, especially at the tourist place where the festival of Mexican sunflower has been yearly organized.
 
 

Effects of Climate Change on Weeds and Invasive Alien Plants in Sri Lankan Agro-Ecosystems: Policy and Management Implications

Changes in the climate have worsen the problems caused by weeds and invasive alien plants (IAPs) in agro-ecosystems at global scale resulting from their changes in the range and population densities. Over the past six decades, Sri Lanka has experienced a slow but steady increase in annual environmental temperature by 0.01–0.03°C. Increasing extreme events of rainfall, wetter wet seasons, and drier dry seasons are some of the characteristic features of the changes in the climate observed in Sri Lanka over the years. The Ministry of Environment (MOE) in Sri Lanka has established a National Invasive Species Specialist Group (NISSG) in 2012 and adopted the National Policy on Invasive Alien Species (IAS) in Sri Lanka, Strategies and Action Plan in 2016. Further, the MOE has developed and adopted protocols to assess the risk of IAS at pre- and post-entry level to the country while incorporating climate change concerns. Periodic risk assessments have being carried out to prioritize actions against IAS in Sri Lanka. The Ministry of Agriculture as adopted a National Weed Strategy (NWS) and has identified the Weeds of National Significance (WONS) under different priority crops. A study done in 2014 has clearly shown that weed control costs in agricultural lands in several district of Sri Lanka were nearly doubled during the years that experiencedEl NiñoSouthern Oscillation (ENSO). Further, studies have clearly indicated that IAPs also survive, expand and impact the continuously disturbed environments in agro-ecosystems.Panicum trichocladum, a species listed as a potential invasive based on the risk assessment done in 2016, has shown an increase in its population density and distribution in Sri Lanka during the last 2–3 years. However, weeds and IAPs in agro-ecosystems have drawn less attention of policy makers, scientists, and practitioners in relation to impact of climate change in island ecosystems. This paper focuses on the scientific evidence reported in agro-ecosystems in Sri Lanka on climate-related impacts on agriculturally important weeds and IAPs, and the efforts made to manage their introduction and spread across the country.

A multiregional assessment of transnational pathways of introduction

Information on the pathways by which alien taxa are introduced to new regions is vital for prioritising policy and management responses to invasions. However, available datasets are often compiled using disparate methods, making comparison and collation of pathway data difficult. Using a standardised framework for recording and categorising pathway data can help to rectify this problem and provide the information necessary to develop indicators for reporting on alien introductions. We combine the Convention on Biological Diversity’s Pathways Categorisation Scheme (CPC) with data compiled by the Invasive Species Specialist Group (ISSG) to report on multiregional trends on alien introduction pathways over the past 200+ years. We found a significant increase in the documented number of multiregional alien introduction events across all pathways of the CPC’s three hierarchical levels. The ‘escape’ pathway is the most common documented pathway used by alien taxa. Transport stowaways via shipping-related pathways are a rapidly increasing contribution to alien introductions. Most alien introduction events were of unknown pathway origin, highlighting the challenge of information gaps in pathway data and reiterating the need for standardised information-gathering practices. Combining the CPC framework with alien introduction pathways data will standardise pathway information and facilitate the development of global indicators of trends in alien introductions and the pathways they use. These indicators have the potential to inform policy and management strategies for preventing future biological invasions and can be downscaled to national and regional levels that are applicable across taxa and ecosystems.

The Convention on Biological Diversity (CBD)’s Post-2020 target on invasive alien species – what should it include and how should it be monitored?

The year 2020 and the next few years are critical for the development of the global biodiversity policy agenda until the mid-21st century, with countries agreeing to a Post-2020 Global Biodiversity Framework under the Convention on Biological Diversity (CBD). Reducing the substantial and still rising impacts of invasive alien species (IAS) on biodiversity will be essential if we are to meet the 2050 Vision where biodiversity is valued, conserved, and restored. A tentative target has been developed by the IUCN Invasive Species Specialist Group (ISSG), and formally submitted to the CBD for consideration in the discussion on the Post-2020 targets. Here, we present properties of this proposal that we regard as essential for an effective Post-2020 Framework. The target should explicitly consider the three main components of biological invasions, i.e. (i) pathways, (ii) species, and (iii) sites; the target should also be (iv) quantitative, (v) supplemented by a set of indicators that can be applied to track progress, and (vi) evaluated at medium- (2030) and long-term (2050) time horizons. We also present a proposed set of indicators to track progress. These properties and indicators are based on the increasing scientific understanding of biological invasions and effectiveness of responses. Achieving an ambitious action-oriented target so that the 2050 Vision can be achieved will require substantial effort and resources, and the cooperation of a wide range of stakeholders.

The identity of the exotic Pterygoplichthys sailfin catfishes in Sri Lanka (Teleostei: Loricariidae).

Invasive alien species (IAS) are a major threat to biodiversity and have contributed to population declines in native species worldwide (Vilà et al. 2011; Gurevitch Padilla 2004). IUCN's Invasive Species Specialist Group lists some 80 invasive or potentially invasive species in Sri Lanka, which is part of a global biodiversity hotspot (Myers et al. 2000; Marambe et al. 2011). The major release of aquatic IAS on the island are routed through the ornamental-fish industry (Marambe et al. 2011; Sudasinghe 2016), though a minority represents deliberate, if unplanned, introductions by governmental and non-governmental agencies (Marambe et al. 2011).

What evidence exists on the effectiveness of different types of olfactory lures as attractants for invasive mammalian predators? A systematic map protocol

BackgroundAlien mammalian predators are a major cause of species extinction and decline globally. Baits and lures, usually human-food based (for example meat, nuts or oils), are widely deployed in trapping programs to attract target species, but their effectiveness compared to other types of olfactory lures, for example social odours or prey odours, has never been systematically examined. Depending on the context, there can be high proportions of non-target captures, for example when targeting feral cats using cage traps, or low capture success, for example, when targeting introduced rats on tropical islands. Here we use a systematic process to map evidence on the effectiveness of different categories of olfactory attractants for invasive mammalian predators within different ecological contexts. We aim to look for where evidence clusters and knowledge gaps occur, for example, across different lure types or across different habitat-types, and highlight opportunities for future research into behaviourally-relevant olfactory lures.MethodsWe will compile evidence from bibliographic databases, online search engines, government websites, specialist sites and expert contacts, and include ‘grey’ literature. Where possible, a Boolean-style full search string will be used, including Population, Intervention and Outcome search terms. Searches will be conducted in English, but a public request to the IUCN SSC Invasive Species Specialist Group (ISSG) will be made for literature including in languages other than English. Search comprehensiveness will be evaluated against 25 benchmark articles known to the authors. We will base inclusion of articles on presence of quantitative data, subject identity (invasive mammalian predator species), comparator (more than one type of olfactory lure assessed or lure compared to a control) and outcome (quantified attraction to lures or controls). Inclusion consistency checks will be performed with 10% of the titles and abstracts and 10% of the full texts. We will critically appraise the literature only on the basis of study design (e.g. appropriate controls) and sample size, rather than interpret the results. Finally, we will develop a searchable literature database accompanied by systematic ‘heat’ maps to visually represent knowledge clusters and gaps within different subsets of evidence, and a narrative synthesis of the evidence.

Risk hotspots for terrestrial plant invaders under climate change at the global scale

Terrestrial plant invaders (TPIs) have a large potential to threaten plant diversity under climate change. To prevent the spread of TPIs under climate change, we must identify the risk hotspots for TPIs. However, the risk hotspots for TPIs have not yet been explicitly addressed at the global scale under climate change. Here, we selected 336 TPIs from the Invasive Species Specialist Group list and used species distribution modelling and Hot Spot Analysis to map the risk hotspots of TPIs based on the terrestrial ecoregions in the current, low and high gas concentration scenarios. The risk hotspots of TPIs were mainly distributed in South America, Europe, Australia, New Zealand and northern and southern Africa. Climate change may decrease the areas of hotspots that allow for TPI expansion, but the potential distribution probabilities of TPIs may increase in the high concentration scenario. Furthermore, TPIs, particularly herbaceous and woody ones, might still expand into critical or endangered ecoregions of these risk hotspots in the current, low and high concentration scenarios. We also need to focus on the impact of TPI expansion on both vulnerable and relatively stable ecoregions due to the increasing potential distribution probabilities of TPIs in risk hotspots and should integrate climate change into the risk assessment of plant invasion in the vulnerable and relatively stable ecoregions.

Managing alien bird species: Time to move beyond “100 of the worst” lists?

SummaryAlien species can cause severe impacts in their introduced ranges and management is challenging due to the large number of such species and the diverse nature and context of their impacts. Lists of the most harmful species, like the “100 of the World’s Worst” list collated by the Invasive Species Specialist Group of the International Union for Conservation of Nature (IUCN) or the “100 of the Worst” invaders in Europe collated by the Delivering Alien Invasive Species Inventories in Europe (DAISIE) project, raise awareness about these impacts among the public, and can guide management decisions. Such lists are mainly based on expert opinion, but in recent years a more objective comparison of impacts has become possible, even between highly diverse taxa. In this study, we use a semi-quantitative generic impact scoring system to assess impacts of the three birds listed among the “100 of the World’s Worst” IUCN list (IUCN100) and the four birds on the list of “100 of the Worst” European invaders by DAISIE (DAISIE100) and to compare their impacts with those of other alien birds not present on the respective lists. We found that generally, both lists include some of the species with the highest impacts in the respective regions (global or Europe), and these species therefore deserve the dubious honour of being listed among the “worst”. However, there are broad overlaps between some species with regards to the impact mechanisms and the related issues of invasions, especially those of the Common Myna Acridotheres tristis and Red-vented Bulbul Pycnonotus cafer on the IUCN100, are very similar which might not warrant listing both species. To make the selection of species on such lists more transparent we suggest moving beyond lists based on expert opinion to a more transparent and defendable system for listing alien species based on published records of their impacts and related mechanisms.

IUCN SSC Invasive Species Specialist Group: invasive alien species information management supporting practitioners, policy makers and decision takers

The Invasive Species Specialist Group (ISSG) is a global network of scientific and policy experts on invasive species, organized under the auspices of the Species Survival Commission (SSC) of the International Union for Conservation of Nature (IUCN). ISSG aims to reduce threats to natural ecosystems and the native species they contain by increasing awareness of invasive alien species, and of ways to prevent, control or eradicate them. Since its establishment, over two decades ago, ISSG has taken the lead on collating, managing and disseminating global invasive species information, promoting practitioner networks and supporting development of policy and regulation aimed at reducing the insidious threat of biological invasions. All this has been accomplished through the development of knowledge products (such as the Global Invasive Species Database (GISD)), promoting dynamic networks such as Aliens-L, advocacy and publications. ISSG has actively catered to emerging needs with activities directed at key areas such as islands, threatened species, protected areas and developing invasive species indicators to support prioritising and monitoring management action. ISSG is working with partners advancing the adoption of a standardised framework of pathway categories and developing criteria for the ranking of known invasive species based on the type and magnitude of impacts. ISSG through participation in the Global Invasive Alien Species Information Partnership (GIASIPartnership) is working with other information providers supporting countries with current and authoritative information to effectively implement Article 8(h), Aichi Biodiversity Target 9 and other related decisions of the Convention on Biological Diversity (CBD) and other Multilateral Environmental Agreements (MEAs) such as the Convention on the Conservation of Migratory Species of Wild Animals (CMS) and the Ramsar Convention on Wetlands.

Evaluation of the Fish Invasiveness Screening Kit (FISK v2) for peninsular Florida

The Fish Invasiveness Screening Kit (FISK) is becoming a popular tool for rapid risk identification of freshwater fishes, with published applications now spanning the globe. Upgrades (i.e., FISK v2) were completed recently to ensure the incorporation of broader climatic zones for its application to the sub-tropical climate of peninsular Florida. The goal of the present study was to evaluate the ability of FISK v2 to identify the potential risk of non-native fishes being invasive in peninsular Florida. The 95 fishes selected for screening were assigned an independent invasiveness ranking using information provided by FishBase and the Invasive Species Specialist Group database. Risk screenings using FISK v2 were then completed separately and independently by five assessors resulting in one to five screenings per taxon. Receiver operating characteristic (ROC) analysis identified a mean threshold value of 10.25 to distinguish between invasive fishes and noninvasive fishes, which, when compared to the independent invasiveness standard, correctly classified 76% of invasive fishes and 88% of noninvasive fishes. This threshold value was considerably lower than many other published calibrations of FISK, emphasizing the importance of regionally focused risk screening. Further supporting these results, 18 (72%) of the high risk species are either established in Florida or have elevated regulatory status by the Florida Fish and Wildlife Conservation Commission. Overall, FISK v2 has proved that it would be a valuable tool for informing management decisions related to the risks of non-native freshwater fishes.

How to communicate on pests and invasive alien plants? Conclusions of the EPPO/CoE/IUCN‐ ISSG/DGAV/UC/ESAC Workshop

How to communicate on pests and invasive alien plants? Conclusions of the EPPO/CoE/IUCN‐ ISSG/DGAV/UC/ESAC Workshop

Future ant invasions in France

SUMMARYAnts are among the worst invasive species, and can have tremendous negative impacts on native biodiversity, agriculture, estates, property and human health. Invasive ants are extremely difficult to control, and thus early detection is essential to prevent ant invasions, in particular through surveillance efforts at ports of entry. This paper assesses the potential distribution of 14 of the worst invasive ant species in France, under current and future climatic conditions. Consensus species distribution models, using five different modelling techniques, three global climate models and two CO2 emission scenarios, indicated that France presented suitable areas for 10/14 species, including five listed on the Invasive Species Specialist Group's selection of the world's 100 worst invasive species. Among these 10 species, eight were predicted to increase their potential range with climate change. Areas with the highest concentration of potential invaders were mainly located along the coastline, especially in the south-west of France, but all departments appeared to be climatically suitable for at least two invasive species. A ranking of climatic suitability per species for 17 major airports and 14 maritime ports indicated that the ports of entry with the highest suitability were located in Biarritz, Toulon and Nice, and the species with the greatest potential distribution in France were Lasius neglectus and Linepithema humile, followed by Solenopsis richteri, Pheidole megacephala and Wasmannia auropunctata.

Alien invaders

Thousands of species have invaded new territories in recent decades, often aided by global trade and man-made habitat change. While many remain harmless, some may cause serious damage. Therefore, we need improvements in surveillance and in our understanding of which factors make a successful invasion possible.

Update: Decomposing beta diversity

news and update Paulo Borges (University of Azores, Azorean Biodiversity Group), described the Azorean Biodi- versity Portal (http://www.azoresbioportal.angra. uac.pt/) and highlighted the importance of science communication for the general public, putting is- land biodiversity on the web. He also explained the importance of standardized studies and moni- toring of island ecosystems using Long Term Eco- logical Studies (LTER). Frederico Cardigos (representing the Azor- ean and Madeiran Governments) affirmed that along the whole processes of governance and na- ture conservation policies, it is assumed that pub- lic perception is of great importance and has a considerable impact on the way politicians react. In addition he presented the plan of the Azorean Government for the management of both terres- trial and marine environments. Antonio Machado referred that the task is immense and complex, and that as an island de- creases in size and its distance to the mainland increases (isolation), its ecological vulnerabil- ityalso increases, the data is scarcer, and there is insufficient local technical capacity and lack of political commitment. IAS on Islands were discussed by Juan Luis Rodriguez Luengo (Canary Islands) that presented the TOP100 Macaronesian initiative, Piero Geno- vesi (Italy) that presented the ISSG (Invasive Spe- cies Specialist Group), Lucilla Carnevali that pre- sented the database on IAS in European Islands and Sarah Brunel (EPPO), that talked on Biosecu- rity in Islands – Using Plant heath instrument to control IAS. Invasive species were considered the ISSN 1948-6596 most important problem to the conservation of the native island biota and ecosystems. By the end of the meeting the Priorities for action and Proposals to the Standing Committee of the Bern Convention were discussed under the coordination of Eladio Fernandez-Galiano. Sugges- tions included: EU legislation dedicated to IAS on islands; portfolio of biodiversity on islands; man- ual of best practices; establishing working groups (climate change; IAS; IUCN criteria revision adapted to islands and invertebrates; communica- tion improvement); for the parties – special atten- tion to natural systems on islands promoting ini- tiatives of biodiversity information gathering. A major challenge of this group of Experts on Island Biological Diversity is to influence the policy-makers, managers and general public on the importance of putting special resources for the conservation of island biota and ecosystems, maintaining also a sustainable life for island hu- man populations. The solid experience and knowledge in is- land ecosystems of most of the experts that par- ticipated in this meeting, together with the com- mitment of local politicians is a strong indicator that the goals of this meeting will be entirely achieved, and that we will create an international network of expertise in island studies. Paulo A. V. Borges Azorean Biodiversity Group, University of the Azores, Portugal http://cita.angra.uac.pt/biodiversidade/ update Decomposing beta diversity Baselga (2009) proposes a creative analysis to de- compose patterns of beta diversity into effects of nestedness and species turnover. This kind of ap- proach moves us closer to distinguishing different mechanisms that can contribute to observed measures of beta diversity. Two additional consid- erations will help to improve this analysis. First, more effort should be devoted to carefully exploring the statistical performance of this index with artificial data sets that have speci- fied amounts of randomness and structure. The analyses presented in Figures 2 and 3 are an excel- lent start, but we need an expanded analysis of different kinds of benchmark matrices to evaluate the potential for Type I errors (incorrectly reject- ing a true null hypothesis) and Type II errors (incorrectly accepting a false null hypothesis). These kinds of tests are challenging because they © 2009 the authors; journal compilation © 2009 The International Biogeography Society — frontiers of biogeography 1.2, 2009

Deciphering complex relationships between apparently unrelated species

Rabbits are considered by biologists to be among the worst invasive species. Their impact on invaded ecosystems, epitomized in Australia and on islands worldwide (e.g. North, Bullock & Dulloo, 1994; Williams et al., 1995; Burbidge & Moris, 2001; Garzon-Machado et al., 2010), has earned them a well-deserved place in the infamous Invasive Species Specialist Group’s ‘100 of the Worst Invasive Alien Species’ list. Rabbits are capable of profoundly altering communities, ecosystems and landscapes by sapping biodiversity and biomass from the basic trophic levels of often fragile ecosystems. However, they also have more complex, and hitherto seldom documented effects on higher trophic levels (Zedler & Black, 1992; Priddel, Carlile & Wheeler, 2000; Oliver, LuqueLarena & Lambin, 2009; Denyer, Hartley & John, 2010). In the context of a few, but loud voices attempting to question the importance of alien invasive species (but see Lambertini et al., 2011; Lockwood, Hoopes & Marchetti, 2011), the paper by Brodier et al. (2011) is well timed. It reminds us that restoration ecology and the fight against biodiversity loss are possible, in particular on islands, as they generally have many endemic and threatened species. This paper also highlights two very important, yet previously overlooked points. The first is the importance of longterm follow-up after restoration programmes. The second is the need to consider the indirect (and consequently often hidden) effects that alien invasive species can have on seemingly unconnected species. By monitoring the populations, several petrel species and their avian predator (the brown skua, Catharacta skua) following the removal of rabbits, Brodier et al. (2011) show that rabbits compete for space with blue petrels, Halobaena caerulea. Following rabbit eradication, the competition for burrows was removed and the blue petrel population increased up to eightfold in a few generations. Brown skua also increased their survivorship in response to the increase in its main prey, the blue petrel. Interestingly, the population of another petrel, the Antarctic prion, Pachyptila desolata, was also impacted by the rabbits. Following the eradication, the Antarctic prion population declined fourfold (to exclusion) in areas of deep soil and remained stable where the soil was too shallow for blue petrel (and rabbits). The resulting system, illustrated in Fig. 1, shows that one unexpected, and up to now unreported, effect of rabbits was to erode the niche partitioning of nesting seabirds on the island. Removing the rabbits led to both a competitor release (of the blue petrel, freed from the competition with rabbits) and to an apparent competitor release (of the shared predator, the brown skua, boosted by increased blue petrel availability). The combination of direct and indirect interactions restricted Antarctic prions to shallow soil areas, less favoured by the blue petrel. This neat system shows how alien invasive species can have effects beyond the trophic level constituting their resources. The contrast between the spectacular recovery of the blue petrel, the increased survival but stable number of skua breeding pairs and the decrease of the Antarctic prion also illustrates well the difficulties to forecast outcomes that conservation program may face even in relatively simple trophic webs. This is especially so in the current context of global climate change, which already affects subantarctic islands (Chapuis, Frenot & Lebouvier, 2004; Dowding et al., 2009), and which could have played a role in the system, for example, in the delayed recovery of the skua. Monitoring population densities, survival and predator diet, every year, on this remote, far reaching island, for long after the rabbit eradication might have been seen as a risky bet. As it turned out, the bet paid off, in the best currency ever: knowledge and understanding. Deciphering the indirect effects a terrestrial herbivore can have on a community of seabirds with which they have few interactions if any, is crucial in our battle against alien invasive species (Bergstrom et al., 2009; Genovesi, 2011). It demonstrates very well that if we were to ‘judge alien species only on their effects’, we would miss all but the tip of the iceberg and would allow important but unapparent, indirect effects of alien invasive species on native ecosystems. One regret from this study is that the monitoring effort conducted after rabbit eradication was not also implemented Animal Conservation. Print ISSN 1367-9430

Pattern versus process: broadening the view of marine invasive species

Invasive species represent those that have taken up resi-dence outside of their normal geographic range, eitherthrough natural or anthropogenic mechanisms. Much hasbeen made about the eVects of invasive species on nativeecosystems, particularly if the invasion can be traced tohuman activities. The perceived threats that invasive spe-cies cause have prompted the establishment of severalgroups whose sole purpose is to evaluate, mitigate or con-trol the eVects of invasive species (e.g., the InternationalUnion for Conservation of Nature’s “Invasive Species Spe-cialist Group”). Invasive species cause negative eVects tonative ecosystems and cause losses of biodiversity, don’tthey?In terrestrial and freshwater ecosystems, invasive spe-cies have been shown to have severe eVects on ecosystems,some of which are so detrimental as to have caused extinc-tions of native species (e.g., the brown treesnake,

Endemism Predicts Intrinsic Vulnerability to Nonindigenous Species on Islands

While numerous efforts have been made to identify and quantify factors controlling invasibility of biological communities, less attention has been given to analyzing the expressions of vulnerability to nonindigenous species (NIS). Using the International Union for the Conservation of Nature and Natural Resources Red List database for birds, mammals, and amphibians and the Invasive Species Specialist Group global invasive species database as sources of information, we developed a new indicator for the relative intrinsic vulnerability of islands to NIS. It was calculated from the residuals to the global relationship between the impact of NIS and their exposure to the islands. The impact of NIS was expressed as the proportion of indigenous species threatened by NIS, and the exposure was the number of invasive NIS per number of native species. The residuals corresponded to the variability in impact, about 60%, that was not explained by exposure. The proportion of endemic species on the islands was positively correlated with the relative intrinsic vulnerability and explained about 60% of its variability. The robust relationship between endemism and intrinsic vulnerability reinforces the role of long-term isolation for the fate of island indigenous species to biological invasions and is useful in identifying vulnerable environments without having a specific invader in mind.