Improved design method for biosecurity surveillance and early detection of non-indigenous rats

A recent advance in biosecurity surveillance design aims to benefit island conservation through early and improved detection of incursions by non-indigenous species. The novel aspects of the design are that it achieves a specified power of detection in a cost-managed system, while acknowledging heterogeneity of risk in the study area and stratifying the area to target surveillance deployment. The design also utilises a variety of surveillance system components, such as formal scientific surveys, trapping methods, and incidental sightings by non-biologist observers. These advances in design were applied to black rats (Rattus rattus) representing the group of invasive rats including R. norvegicus, and R. exulans, which are potential threats to Barrow Island, Australia, a high value conservation nature reserve where a proposed liquefied natural gas development is a potential source of incursions. Rats are important to consider as they are prevalent invaders worldwide, difficult to detect early when present in low numbers, and able to spread and establish relatively quickly after arrival. The ?exemplar? design for the black rat is then applied in a manner that enables the detection of a range of non-indigenous species of rat that could potentially be introduced. Many of the design decisions were based on expert opinion as data gaps exist in empirical data. The surveillance system was able to take into account factors such as collateral effects on native species, the availability of limited resources on an offshore island, financial costs, demands on expertise and other logistical constraints. We demonstrate the flexibility and robustness of the surveillance system and discuss how it could be updated as empirical data are collected to supplement expert opinion and provide a basis for adaptive management. Overall, the surveillance system promotes an efficient use of resources while providing defined power to detect early rat incursions, translating to reduced environmental, resourcing and financial costs.     

A new approach to molecular biosurveillance of invasive species using DNA metabarcoding

Non‐indigenous species (NIS) reach every corner of the world, at times wreaking havoc on ecosystems and costing the global economy billions of dollars. A rapid and accurate biosurveillance tool tailored to a particular biogeographic region is needed to detect NIS when they are first introduced into an area as traditional detection methods are expensive and require specialized expertise. Metabarcoding of environmental and community DNA meets those biosurveillance requirements; a novel tool tailored to the Northwest Pacific Ocean is presented here using an approach that could revolutionize early detection of NIS. Eight newly designed genetic markers for multiple gene regions were implemented to meet the stringent taxonomic requirements for the detection of NIS across four major marine phyla. The tool was considered highly successful because it identified 12 known NIS in the study area and a further seven species representing potential new records. Overall community composition detected here was statistically different between substrate types; zooplankton sampling accounted for significantly higher species richness than filtered sea water in most cases, but this was dominated by mollusk and arthropod species. Both substrate types sampled were required to identify the wide taxonomic breadth of known NIS in the study area. Intensive sampling is known to be paramount for the detection of rare species, including new incursions of NIS, thus it is recommended to include diverse DNA sampling protocols based on species’ life‐history characteristics for broad detection capacity. Application of a metabarcoding‐based molecular biosurveillance tool optimized for biogeographic regions enables rapid and accurate early detection across a wide taxonomic range to allow quick implementation of eradication or control efforts and potentially mitigate some of the devastating effects of NIS worldwide.     

Biosecurity surveillance design: detecting non-indigenous vertebrate introductions using risk and power

Ecosystems can be severely damaged by the introduction, establishment and spread of non-indigenous species (NIS) including vertebrates, invertebrates and plants. Development and use of natural areas poses a biosecurity risk regarding the introduction of increase NIS invasion risks, so biosecurity systems including prevention and detection measures are required. Even with the most rigorous biosecurity efforts, there is potential for NIS to evade quarantine and go on to establish and spread. The cost of such an event can be great, both environmentally and financially (e.g. containment/ management or eradication). We have developed a surveillance design methodology, for an application where increased use of a natural area may result in NIS incursions, even with extensive biosecurity systems. The surveillance design methodology acknowledges heterogeneity of risk in the study area and stratifies the area to optimise surveillance deployment, achieving great efficiencies and improvement in statistical power of detection. Many of the risk decisions require lack data and so the system incorporates expert opinion with available data. The design covers the broad range of potential NIS that may be introduced by using exemplar species and a variety of surveillance system components (SSCs) (such as a combination of formal scientific surveys, trapping methods, and casual observation) distributed optimally over time and space. The mix of SSCs can be manipulated to take into account such factors as their relative financial costs and demands on expertise. The methodology has the flexibility to be applied to various groups of potential NIS (e.g. vertebrates, invertebrates and plants), and the design can evolve as data are collected (adaptive management). Overall, the surveillance design methodology allows for an efficient use of resources, providing sufficient power to detect incursions, resulting in reduced environmental and financial costs from NIS incursions.     

Improved surveillance for early detection of a potential invasive species: the alien Rose-ringed parakeet <Emphasis Type="Italic">Psittacula krameri</Emphasis> in Australia

The Rose-ringed parakeet Psittacula krameri is the most widely introduced parrot in the world, and is an important agricultural pest and competitor with native wildlife. In Australia, it is classified as an ‘extreme threat’, yet captive individuals frequently escape into the wild. The distribution and frequency of incursions are currently unknown, as are the potential impacts of the species in Australia. This lack of critical ecological information greatly limits effective biosecurity surveillance and decision-making efforts. We compiled a unique dataset, which combined passive surveillance sources from government and online resources, for all available information on parakeet detections at-large in Australia. We investigated whether geographic variables successfully predicted parakeet incursions, and used species distribution models to assess the potential distribution and economic impacts on agricultural assets. We recorded 864 incursions for the period 1999–2013; mostly escaped birds reported to missing animal websites. Escapes were reported most frequently within, or around, large cities. Incursions were best predicted by factors related to human presence and activity, such as global human footprint and intensive land uses. We recommend surveillance of high (predicted) establishment areas adjacent to cities where a feral parakeet population could most affect horticultural production. Novel passive surveillance datasets combined with species distribution models can be used to identify the regions where potential invasive species are most likely to establish. Subsequently, active surveillance can be targeted to the areas of highest predicted potential risk. We recommend an integrated approach that includes outreach programs involving local communities, as well as traditional biosecurity surveillance, for detecting new incursions.     

When does invasive species removal lead to ecological recovery? Implications for management success

The primary goal of invasive species management is to eliminate or reduce populations of invasive species. Although management efforts are often motivated by broader goals such as to reduce the negative impacts of invasive species on ecosystems and society, there has been little assessment of the consistency between population-based (e.g., removing invaders) and broader goals (e.g., recovery of ecological systems) for invasive species management. To address this, we conducted a comprehensive review of studies (N = 151) that removed invasive species and assessed ecological recovery over time. We found positive or mixed outcomes in most cases, but 31% of the time ecological recovery did not occur or there were negative ecological outcomes, such as increases in non-target invasive species. Ecological recovery was more likely in areas with relatively little anthropogenic disturbance and few other invaders, and for the recovery of animal populations and communities compared to plant communities and ecosystem processes. Elements of management protocols, such as whether invaders were eradicated (completely removed) versus aggressively suppressed (≥90% removed), did not affect the likelihood of ecological recovery. Our findings highlight the importance of considering broader goals and unintended outcomes when designing and implementing invasive species management programs.     

Environmental DNA detection of aquatic invasive plants in lab mesocosm and natural field conditions

Aquatic invasive plant species cause negative impacts to economies and ecosystems worldwide. Traditional survey methods, while necessary, often do not result in timely detections of aquatic invaders, which can be cryptic, difficult to identify, and exhibit very rapid growth and reproduction rates. Environmental DNA (eDNA) is a relatively new method that has been used to detect multiple types of animals in freshwater and marine ecosystems through tissues naturally shed from the organism into the water column or sediment. While eDNA detection has proven highly effective in the detection of aquatic animals, we know less about the efficacy of eDNA as an effective surveillance tool for aquatic plants. To address this disparity, we designed mesocosm experiments with Elodea species to determine the ability to detect accumulation and degradation of the DNA signal for aquatic plants, followed by field surveillance of the highly invasive Hydrilla verticillata in freshwaters across several U.S. geographic regions. In both lab and field experiments, we designed a high sensitivity quantitative PCR assay to detect the aquatic plant species. In both experiments, plant eDNA detection was successful; we saw accumulation of DNA when plants were introduced to tanks and a decrease in DNA over time after plants were removed. We detected eDNA in the field in areas of known Hydrilla distribution. Employing eDNA detection for aquatic plants will strengthen efforts for early detection and rapid response of invaders in global freshwater ecosystems.     

Invasive cane toads might initiate cascades of direct and indirect effects in a terrestrial ecosystem

Understanding the impacts that invasive vertebrates have on terrestrial ecosystems extends primarily to invaders’ impacts on species with which they interact directly through mechanisms such as predation, competition and habitat modification. In addition to direct effects, invaders can also initiate ecological cascades via indirect population level effects on species with which they do not directly interact. However, evidence that invasive vertebrates initiate ecological cascades in terrestrial ecosystems remains scarce. Here, we ask whether the invasion of the cane toad, a vertebrate invader that is toxic to many of Australia’s vertebrate predators, has induced ecological cascades in a semi-arid rangeland. We compared activity of a large predatory lizard, the sand-goanna, and abundances of smaller lizards preyed upon by goannas in areas of high toad activity near toads’ dry season refuges and areas of low toad activity distant from toads’ dry season refuges. Consistent with the hypothesis that toad invasion has led to declines of native predators susceptible to poisoning, goanna activity was lower in areas of high toad activity. Consistent with the hypothesis that toad-induced goanna decline lead to increases in abundance the prey of goannas, smaller lizards were more abundant in areas of high toad activity. Structural equation modelling showed a positive correlation between goanna activity and distance from dry season refuge habitats used by toads. The abundances of small lizards was correlated negatively with goanna activity and distance from dry season refuges of toads. Our findings provide support for the notion that invasions by terrestrial vertebrates can trigger ecological cascades.     

Smart moves: effects of relative brain size on establishment success of invasive amphibians and reptiles

Brain size relative to body size varies considerably among animals, but the ecological consequences of that variation remain poorly understood. Plausibly, larger brains confer increased behavioural flexibility, and an ability to respond to novel challenges. In keeping with that hypothesis, successful invasive species of birds and mammals that flourish after translocation to a new area tend to have larger brains than do unsuccessful invaders. We found the same pattern in ectothermic terrestrial vertebrates. Brain size relative to body size was larger in species of amphibians and reptiles reported to be successful invaders, compared to species that failed to thrive after translocation to new sites. This pattern was found in six of seven global biogeographic realms; the exception (where relatively larger brains did not facilitate invasion success) was Australasia. Establishment success was also higher in amphibian and reptile families with larger relative brain sizes. Future work could usefully explore whether invasion success is differentially associated with enlargement of specific parts of the brain (as predicted by the functional role of the forebrain in promoting behavioural flexibility), or with a general size increase (suggesting that invasion success is facilitated by enhanced perceptual and motor skills, as well as cognitive ability).     

Sediment Toxicity Testing for Prospective Risk Assessment—A New Framework and How to Establish It

There is a recognized need to design a new framework for sediment toxicity testing that meets current scientific standards and regulatory requirements, such as reliable assessment of toxicity, which prevents any harmful effects on biodiversity, a strong capability to predict population- and community-level effects, and applicability of the results to decision-making. We propose a new framework for prospective sediment toxicity testing, and suggest solutions to the key methodological challenges that hinder establishment of this framework (comparison of sensitivities, design of test batteries, consideration of different exposure routes, extrapolations to population and community levels, use of test results for decision-making). The proposed framework consists of the following three units: test-battery system, higher-tier testing systems and additional ecological modeling, and a decision support system. The key methodologies proposed to establish this framework are compound-tailored test-battery use approach, relative sensitivity distribution analysis, toxicity tests that combine bacteria and arthropods, micro- and mesocosms studies, population and community models, and model-driven decision support systems. The proposed framework, as well as the key methods mentioned above, has the potential to improve not only prospective toxicity testing for sediments, but also ecological risk assessment in general.     

Restoration through reassembly: plant traits and invasion resistance

One of the greatest challenges for ecological restoration is to create or reassemble plant communities that are resistant to invasion by exotic species. We examine how concepts pertaining to the assembly of plant communities can be used to strengthen resistance to invasion in restored communities. Community ecology theory predicts that an invasive species will be unlikely to establish if there is a species with similar traits present in the resident community or if available niches are filled. Therefore, successful restoration efforts should select native species with traits similar to likely invaders and include a diversity of functional traits. The success of trait-based approaches to restoration will depend largely on the diversity of invaders, on the strength of environmental factors and on dispersal dynamics of invasive and native species.     

Risk assessment for invasiveness differs for aquatic and terrestrial plant species

Predictive tools for preventing introduction of new species with high probability of becoming invasive in the U.S. must effectively distinguish non-invasive from invasive species. The Australian Weed Risk Assessment system (WRA) has been demonstrated to meet this requirement for terrestrial vascular plants. However, this system weights aquatic plants heavily toward the conclusion of invasiveness. We evaluated the accuracy of the WRA for 149 non-native aquatic species in the U.S., of which 33 are major invaders, 32 are minor invaders and 84 are non-invaders. The WRA predicted that all of the major invaders would be invasive, but also predicted that 83% of the non-invaders would be invasive. Only 1% of the non-invaders were correctly identified and 16% needed further evaluation. The resulting overall accuracy was 33%, dominated by scores for invaders. While the overall accuracy increased to 57% when the points assigned to aquatic life forms were removed, 57% of the non-invaders required further evaluation rather than were identified as having low probability of naturalizing. Discrimination between non-invaders and invaders would require an increase in the threshold score from the standard of 6 for this system to 19. That higher threshold resulted in accurate identification of 89% of the non-invaders and over 75% of the major invaders. Either further testing for definition of the optimal threshold or a separate screening system will be necessary for accurately predicting which freshwater aquatic plants are high risks for becoming invasive.     

Adult mosquito trap sensitivity for detecting exotic mosquito incursions and eradication: a study using EVS traps and the Australian southern saltmarsh mosquito, Aedes camptorhynchus

Adult mosquito traps are commonly used in biosecurity surveillance for the detection of exotic mosquito incursions or for the demonstration of elimination. However, traps are typically deployed without knowledge of how many are required for detecting differing numbers of the target species. The aim of this study was to determine the sensitivity (i.e., detection probability) provided by carbon dioxide-baited EVS traps for adult female Australian southern saltmarsh mosquitoes, Aedes camptorhynchus, a recent biosecurity problem for New Zealand. A mark-release-recapture study of three concurrently released cohorts (sized 56, 296, and 960), recaptured over four days with a matrix of 20 traps, was conducted in Australia. The detection probability for different numbers of traps and cohorts of different sizes was determined by random sampling of recapture data. Detection probability ranged from approximately 0.3 for a single trap detecting a cohort of 56 mosquitoes to 1.0 (certainty of detection) when seven or more traps were used. For detection of adult Ae. camptorhynchus around a known source, a matrix of traps provides a strong probability of detection. Conversely, the use of single traps deployed over very large areas to detect mosquitoes of unknown entry pathway is unlikely to be successful. These findings have implications for the design of mosquito surveillance for biosecurity.     

Model to track wild birds for avian influenza by means of population dynamics and surveillance information

Design, sampling and data interpretation constitute an important challenge for wildlife surveillance of avian influenza viruses (AIV). The aim of this study was to construct a model to improve and enhance identification in both different periods and locations of avian species likely at high risk of contact with AIV in a specific wetland. This study presents an individual-based stochastic model for the Ebre Delta as an example of this appliance. Based on the Monte-Carlo method, the model simulates the dynamics of the spread of AIV among wild birds in a natural park following introduction of an infected bird. Data on wild bird species population, apparent AIV prevalence recorded in wild birds during the period of study, and ecological information on factors such as behaviour, contact rates or patterns of movements of waterfowl were incorporated as inputs of the model. From these inputs, the model predicted those species that would introduce most of AIV in different periods and those species and areas that would be at high risk as a consequence of the spread of these AIV incursions. This method can serve as a complementary tool to previous studies to optimize the allocation of the limited AI surveillance resources in a local complex ecosystem. However, this study indicates that in order to predict the evolution of the spread of AIV at the local scale, there is a need for further research on the identification of host factors involved in the interspecies transmission of AIV.     

Herbaceous invaders in temperate forests: a systematic review of their ecology and proposed mechanisms of invasion

We present a systematic literature review of exotic understory forest herbaceous invasions with a focus on the forests of East Asia (EAS) and Eastern North America (ENA), two dominant regions of the north temperate deciduous forest biome. We examined the biogeographic origins of herbaceous invaders in EAS and ENA forests, summarized their life histories and ecology, and compiled the relevant literature on the 10 leading mechanistic hypotheses proposed for these invasions. We asked whether invasions of EAS and ENA forests by herbs are shared between regions, and whether a common suite of ecological traits unite these invaders into a functionally distinct group. In a focused summary of the empirical literature, we investigated if leading hypothesized mechanisms for biological invasions at large are also invoked and supported for this ecologically important, but relatively understudied, group of species. In contrast to ENA, forest invaders in EAS are overwhelmingly herbaceous (78% of forest invasions vs. 34% for ENA) and originate from different regions. Plant families represented and species traits between regions differed. Within a single species, multiple invasion mechanisms were often supported, highlighting the need for future research that simultaneously investigates multiple mechanistic hypotheses. Further, because results for a single invader often differed across space and time, a shift in focus to incorporate the complex dynamics across temporal and spatial scales with the consideration of spatial heterogeneity and the interplays among natural and anthropogenic factors to study exotic invasions is needed.     

Hotspots of plant invasion predicted by propagule pressure and ecosystem characteristics

Aim Biological invasions pose a major conservation threat and are occurring at an unprecedented rate. Disproportionate levels of invasion across the landscape indicate that propagule pressure and ecosystem characteristics can mediate invasion success. However, most invasion predictions relate to species’ characteristics (invasiveness) and habitat requirements. Given myriad invaders and the inability to generalize from single‐species studies, more general predictions about invasion are required. We present a simple new method for characterizing and predicting landscape susceptibility to invasion that is not species‐specific. Location Corangamite catchment (13,340 km²), south‐east Australia. Methods Using spatially referenced data on the locations of non‐native plant species, we modelled their expected proportional cover as a function of a site’s environmental conditions and geographic location. Models were built as boosted regression trees (BRTs). Results On average, the BRTs explained 38% of variation in occupancy and abundance of all exotic species and exotic forbs. Variables indicating propagule pressure, human impacts, abiotic and community characteristics were rated as the top four most influential variables in each model. Presumably reflecting higher propagule pressure and resource availability, invasion was highest near edges of vegetation fragments and areas of human activity. Sites with high vegetation cover had higher probability of occupancy but lower proportional cover of invaders, the latter trend suggesting a form of biotic resistance. Invasion patterns varied little in time despite the data spanning 34 years. Main conclusions To our knowledge, this is the first multispecies model based on occupancy and abundance data used to predict invasion risk at the landscape scale. Our approach is flexible and can be applied in different biomes, at multiple scales and for different taxonomic groups. Quantifying general patterns and processes of plant invasion will increase understanding of invasion and community ecology. Predicting invasion risk enables spatial prioritization of weed surveillance and control.     

Management of invasive plants through ecological resistance

Despite debates on the real impact of plant invasion on native biodiversity, there remain many situations where exotic invasive plants must be managed and habitats restored. Restoration practices that build on plant community assembly principles could be useful to delay or prevent re-invasion after control, but there are still few syntheses of the biodiversity theory, ecological mechanisms and experimental evidence relevant to invasive plant management, possibly delaying applications. To provide such a synthesis, we review current knowledge on three key determinants of invasion success: biotic resistance, abiotic constraints, and propagule pressure. We elaborate on the ecological mechanisms at play for each determinant and emphasize, using case studies, their relevance for invasive plant management and ecological restoration. We find evidence that restoring a plant cover can enhance invasion resistance, but the challenge for both research and field applications is to understand how multiple determinants interact in relation to species traits in the fields. Failure to recognize these interactions and their effect on community assembly processes may explain some of the mixed species responses observed. While we need control and restoration case studies with local species at different sites, the development of a coherent, dynamic and adaptive framework around biotic/ecological resistance will have to go beyond the idiosyncrasy of the many species and systems being tested. Emphasizing the functional diversity of the restored community seems a promising approach when facing potentially multiple invaders and/or fluctuating abiotic conditions.     

Terrestrial or marine species distribution model: Why not both? A case study with seabirds

Species reliant on both the terrestrial and marine realms present a challenge for conventional species distribution models (SDMs). For such species, standard single‐realm SDMs may omit key information that could result in decreased model accuracy and performance. Existing approaches to habitat suitability modeling typically do not effectively combine information from multiple realms; this methodological gap can ultimately hamper management efforts for groups such as seabirds, seals, and turtles. This study, for the first time, jointly incorporates both terrestrial information and marine information into a single species distribution model framework. We do this by sampling nearby marine conditions for a given terrestrial point and vice versa using parameters set by each species’ mean maximum foraging distance and then use standard SDM methods to generate habitat suitability predictions; therefore, our method does not rely on post hoc combination of several different models. Using three seabird species with very different ecologies, we investigate whether this new multi‐realm approach can improve our ability to identify suitable habitats for these species. Results show that incorporating terrestrial information into marine SDMs, or vice versa, generally improves model performance, sometimes drastically. However, there is considerable variability between species in the level of improvement as well as in the particular method that produces the most improvement. Our approach provides a repeatable and transparent method to combine information from multiple ecological realms in a single SDM framework. Important advantages over existing solutions include the opportunity to, firstly, easily combine terrestrial and marine information for species that forage large distances inland or out to sea and, secondly, consider interactions between terrestrial and marine variables.     

Seasonal and ontological variation in diet and age‐related differences in prey choice,by an insectivorous songbird

The diet of an individual animal is subject to change over time, both in response to short‐term food fluctuations and over longer time scales as an individual ages and meets different challenges over its life cycle. A metabarcoding approach was used to elucidate the diet of different life stages of a migratory songbird, the Eurasian reed warbler (Acrocephalus scirpaceus) over the 2017 summer breeding season in Somerset, the United Kingdom. The feces of adult, juvenile, and nestling warblers were screened for invertebrate DNA, enabling the identification of prey species. Dietary analysis was coupled with monitoring of Diptera in the field using yellow sticky traps. Seasonal changes in warbler diet were subtle, whereas age class had a greater influence on overall diet composition. Age classes showed high dietary overlap, but significant dietary differences were mediated through the selection of prey; (i) from different taxonomic groups, (ii) with different habitat origins (aquatic vs. terrestrial), and (iii) of different average approximate sizes. Our results highlight the value of metabarcoding data for enhancing ecological studies of insectivores in dynamic environments.     

Cross-habitat effects shape the ecosystem consequences of co-invasion by a pelagic and a benthic consumer

Invasive species can have major impacts on ecosystems, yet little work has addressed the combined effects of multiple invaders that exploit different habitats. Two common invaders in aquatic systems are pelagic fishes and crayfishes. Pelagic-oriented fish effects are typically strong on the pelagic food web, whereas crayfish effects are strong on the benthic food web. Thus, co-invasion may generate strong ecological responses in both habitats. We tested the effects of co-invasion on experimental pond ecosystems using two widespread invasive species, one pelagic (western mosquitofish) and one benthic (red swamp crayfish). As expected, mosquitofish had strong effects on the pelagic food web, reducing the abundance of Daphnia and causing a strong trophic cascade (increase in phytoplankton). Crayfish had strong effects on the benthic food web, reducing the abundance of benthic filamentous algae. Yet, we also found evidence for important cross-habitat effects. Mosquitofish treatments reduced the biomass of benthic filamentous algae, and crayfish treatments increased Daphnia and phytoplankton abundance. Combined effects of mosquitofish and crayfish were primarily positively or negatively additive, and completely offsetting for some responses, including gross primary production (GPP). Though co-invasion did not affect GPP, it strongly shifted primary production from the benthos into the water column. Effects on snail abundance revealed an interaction; snail abundance decreased only in the presence of both invaders. These results suggest that cross-habitat effects of co-invaders may lead to a variety of ecological outcomes; some of which may be unpredictable based on an understanding of each invader alone.     

Cydippid ctenophores in the coastal waters of Svalbard: is it only Mertensia ovum?

Threat of potential arrival of non-indigenous species is increasing, particularly in the high Arctic, due to ecological shifts expected from climate change and increasing shipping traffic, facilitating long-distance transport of invaders. Hence, knowledge on the species present currently is crucial to assess the potential ecological impact of the non-indigenous species in the future. Ctenophores, and gelatinous zooplankton generally, are poorly known due to identification challenges and lack of systematic monitoring programmes. Yet, they are known to play important roles in the world’s ocean ecosystems and share physiological attributes making them exploit the changing environmental conditions better compared to most other zooplankton groups. Here, we report the co-occurrence of Mertensia ovum, Euplokamis sp. and an unidentified mertensiid-like species in the high Arctic, in the Svalbard archipelago region, based on a combination of morphological and molecular identification methods. This is a valuable first step toward establishing a baseline for future ecological studies, monitoring of climate impacts and assessing the threat of introduced species in the high Arctic.