Introduction Of Exotic Species Research Articles

Establishment potential across South Korea for two gecko species, Gekko japonicus and G. swinhonis, adapted to different climates

The introduction of exotic species and the associated impacts are increasing worldwide due to the development and increase in transportation and international trade. As new populations of the non-native Gekko japonicus and G. swinhonis have recently been discovered in South Korea, this study was conducted to investigate the distribution of these species, evaluate the establishment potential of non-native populations and infer their routes of introduction. The study comprised targeted field surveys around the major international ports, generation of ecological niche models (ENMs), based on the known distributions and comparison of the ecological niches of the two species. The results suggest that G. japonicus and G. swinhonis are primarily distributed in the humid subtropical climate (Cfa) and the monsoon-influenced hot-summer humid continental climate (Dwa), respectively. According to the ENMs predicted across South Korea, suitable habitats for G. japonicus were located along the western and southern coasts of the country, whereas those for G. swinhonis were predicted along the western coastal regions and several major cities inland. These distributional patterns may be attributed to adaptations of the two gecko congeners to distinct climatic conditions leading to divergent ecological niches. Considering the known distributions of the two species in South Korea, the most likely routes of introduction are accidental translocations through international trade and the inland populations most likely originated from human-mediated dispersals along the major rivers. This study highlights the need to implement quarantine procedures for international cargo arriving in South Korea. Additional field surveys are further recommended to focus on urban areas adjacent to international ports and major rivers to curtail further introductions of non-native geckos.

The Dragonflies and Damselflies (Insecta: Odonata) of Canada: species list, geographical distribution, status, and conservation ranks.

As of August 2023, 220 species in 57 genera and 10 families of damselflies and dragonflies (Insecta: Odonata) are recorded for Canada. Since the publication of the first edition in 2005, 14 species have been added to the list; one,Neurocordulia obsoleta (Say) has been removed because of a misidentification and another, Sympetrum occidentale, has been to synonymy. Conservation ranks are given for species in all 13 provinces and territories. English and French names for all listed species are included. Literature sources are discussed and presented, as is information on species status and the addition and exclusion of species. Sections on taxonomy and variation, subspecies, presumed hybrids, the introduction of exotic species, notable range extensions and observations, and conservation and protection are also provided.

Pontederia crassipes invasiveness on Jeju island is linked to a decline in water pH and climate change-driven overwintering

Freshwater ecosystems are vulnerable to the invasion of exotic aquatic plant species because of the great likelihood of the introduction of exotic species, and the lack of barriers that block introduced species. Water hyacinth, Pontederia crassipes Mart., is one of the world’s most invasive alien plant species damaging freshwater ecosystems worldwide. Here, we monitored the water hyacinth population on Jeju island, Korea, to assess current invasion risks. Furthermore, we investigated how water hyacinth affects water pH because pH is an important determinant of the distribution of other aquatic plants, and thus a good indicator of aquatic ecosystem health. Water containing water hyacinth had a pH of 5.3, while that with water hyacinth and soil had a pH of 4.8 72 hours after the start of the experiment. Water hyacinth extracts contained shikimic acid, stearic acid, and palmitic acid, which are possible compounds that caused a decline in water pH. Water hyacinth also inhibited the growth of the aquatic plant species, Spirodela polyrhiza and Lemna perpusilla. These results imply that invasion of water hyacinth adversely impacts the abiotic and biotic characteristics of aquatic ecosystems. Moreover, monitoring the water hyacinth population suggests that this invasive aquatic plant overwinters on Jeju island. Therefore, regular monitoring and subsequent control of water hyacinth population can prevent its expansion in the aquatic habitats of Jeju island and the southern region of the Korean peninsula.

Target, tool, tenure and timing: the four T’s limiting the impact of traditional hunting in Indonesian Papua

Subsistence hunting has sustained human populations in New Guinea for millennia, without seriously affecting the highest levels of biodiversity on Earth. Recent changes to hunting practices, demographic, social and economic context and the introduction of large exotic species has significantly altered the dynamic of hunting and its potential effects in north-west New Guinea. In this paper we examine contemporary hunting practices of six ethnic groups from highland to coastal sites throughout Papua and West Papua provinces of Indonesia. Semi-structured interviews were used to examine hunting practices as well as customary rules and attitudes associated with hunting in the region and how they have changed in living memory. Each group indicated traditional restrictions on at least one of target, tool, timing or tenure, albeit in varied ways. Six different hunting tools were used and each hunter typically combined several tools while hunting. Religious and cultural factors deeply influenced hunting practices among the communities. We discuss the implications of these findings and conclude with recommendations to integrate local, village level governance and customary practices with regional and national law for more effective conservation and management of wildlife in the region while simultaneously respecting cultural heritage and local ecological knowledge.

The Study of Exotic and Invasive Plant Species in Gullele Botanic Garden, Addis Ababa, Ethiopia

The Gullele Botanic Garden was established to preserve and safeguard indigenous, rare, endemic, endangered, and economically important plant species. The objective of this study was to identify and map the exotic, invasive, and potentially invasive plant species that are present in the garden’s various land use types, such as natural vegetation, plantations, roadsides and garden edges. The research involved laying plots at different distances in each land use type and collecting vegetation data with geo-location information. Sorensen’s similarity index was used to measure the floristic similarity between the sampled land use types. Data on species density and abundance were analyzed using the corresponding formula. The Shannon–Wiener diversity index and evenness were used to compute the diversity of the species in each land use type using R packages. ArcGIS version 10.5 was used to track the geographical distribution and map the exotic, invasive, and potentially invasive species that exist in all land use types of the garden. A total of 80 plant species belonging to 70 genera in 44 families were recorded in the garden. Asteraceae, Myrtaceae, and Fabaceae comprised the highest number of species. Acacia decurrens, Acacia melanoxylon, Cuscuta campestris, Galinsoga parviflora, Nerium oleander, and Cyathula uncinulata were the most prevalent invasive and potentially invasive species. The study found that the roadside and garden edge land use types had the most diverse exotic and invasive plants. The total density of exotic species was 2.36 plants/m2. The potential possibility of these plants in displacing the native plant species is quite high unless the introduction of exotic plant species is inspected and appropriate management strategies for invasive species are put in place.

Trophic history of Hawaiian green turtles as revealed by stable isotope ratios (δ13C, δ15N and δ34S) in the bones of museum specimens

Abstract Understanding consumer trophic status and long‐term dietary changes can yield information about impacts of altered habitats on their ecology. In Hawai'i, coastal ecosystems have been significantly modified by the introduction of invasive seaweeds and mangroves, high nutrient load and overfishing, but so far, much is still to be understood about how these changes have affected the green turtle (Chelonia mydas). This study analyzed stable carbon, nitrogen, and sulfur isotope ratios in the bone tissue of modern and museum specimens of green turtles collected from 1901 to 2020 in Oahu and the North‐western Hawaiian Islands to understand how their isotopic niche has changed through time, a crucial step towards restoring the ecological role of a formerly decimated species. The standard ellipse size and the total area of the convex hull of the isotopic niche of green turtles in three periods (1901–1951, 1992–2008, and 2018–2020) were calculated. The stable isotope values of ancient green turtles (1901–1951) suggest that they relied heavily on macroalgae even before the introduction of exotic species and eutrophication promoted the development of algal pastures. However, a few ancient green turtles relied heavily on seagrasses, and others complemented their macroalgae‐based diets with significant amounts of animal matter. Such diet specialists were missing from the sample of current green sea turtles, suggesting that these foraging strategies are less common or perhaps even absent in the current population. The results suggest that green turtles have converged on the use of the most abundant resource, red macroalgae, likely because of the homogenization and simplification of coastal habitats and food webs due to anthropogenic influences. Restoring the population size of herbivorous fishes and a more diverse ecosystem structure may be necessary to recover the array of trophic strategies formerly present in the Hawaiian green turtle population.

Infectious disease as a driver of declines and extinctions

Abstract Infectious disease is an important driver of extinctions and population declines. With a few exceptions, such as the fungal disease chytridiomycosis in frogs, disease is probably underestimated as a cause of both local and global extinction because it often co-occurs with other more overt drivers of extinction, and its signs can be easily overlooked. Here, we discuss issues around attributing extinction to infectious disease and overview key underlying factors. We then examine the extent to which anthropogenic influences, such as climate change, habitat destruction and exotic species introductions, are likely to lead to increased extinction risk in association with infectious disease. Finally, we discuss strategies to mitigate the threat of extinction due to infectious disease.

Parasites (Monogenea) of tilapias Oreochromis niloticus and Coptodon rendalli (Cichlidae) in a river spring in Brazil.

In the present study, we examined 30 individuals of introduced African cichlids, Oreochromis niloticus and Coptodon rendalli, collected in a river spring of the Pardo River, Paranapanema River basin, southeastern Brazil. Based on morphological and molecular analyses of the partial LSU rDNA gene, we identified four species of monogeneans, Cichlidogyrus tilapiae, C. thurstonae, C. mbirizei, and Scutogyrus longicornis on the gills of O. niloticus, whereas individuals of C. rendalli were infested only with C. papernastrema. This is the first record of C. mbirizei and C. papernastrema in tilapias from Brazil. The ecological consequences of the introduction of exotic species of tilapia such as O. niloticus and C. rendalli along with their monogenean parasites in a wild environment represented by a river spring are discussed. Our new molecular data on Cichlidogyrus and Scutogyrus contribute to the investigation of the phylogenetic interrelationships of these widely distributed genera of monogeneans since their species composition is still unsettled.

Parasitic wasps (Hymenoptera) and Biological Control in Chile: Applications and Potentials

Global biodiversity decline and pollution, along with climate change, directly threaten food security and sovereignty. Unsustainable practices in industrial agriculture, including the introduction of non-native insects exacerbate this environmental crisis. These can invade native habitats and disrupt the ecological balance, leading to biodiversity loss. We created a database of parasitic wasp species used for biological control in Chile, examining the percentage of introduced and native species, introduction timelines, and host interactions. A total of 73% of the Hymenoptera used for biological control in Chile are exotic species. This trend has grown over decades as new species were continuously introduced, resulting in an increasing accumulation of exotic species. We also identified instances of native and introduced parasitoid species sharing the same hosts, potentially causing a spillover effect. Given Chile's high endemism in its insect population, the massive introduction of exotic species could have detrimental consequences for local biodiversity and agricultural ecosystems. Overreliance on non-native pest controllers impedes the use of existing native biological control species, increasing vulnerability to pests adapted to widely used biological control agents. We advocate for prioritizing local and native parasitic wasps to ensure long-lasting, and sustainable agriculture production in Chile while mitigating the negative impacts of exotic species.

Analysis of population size of Pterygoplichthys multiradiatus and its intake of microplastics in streams with different land uses

Most freshwater habitats have been substantially affected by anthropogenic factors such as fish introductions, plastic pollution, and river regulation. Urban rivers are highly vulnerable to impacts associated with land use changes resulting from increasing urbanization, including altering habitat and establishing aquatic biological communities in these areas. In turn, the introduction of exotic species into sensitive and threatened ecosystems such as tropical urban streams and their rapid establishment, such as Pterygoplichthys multiradiatus, was used as an ecological model to determine the relative population size of the species. Also, the species was used to evaluate the presence of microplastics (MPs) in the gastrointestinal tract (GIT) of fish in rivers with different land use history. Our results showed significant differences in pleco abundance between areas with high and low urban (LU) development in the watersheds. The study demonstrated that abiotic environmental factors directly influence the relative abundance of plecos at the range and watershed scales. In a total of 42 fish examined, only 85.7% showed MPs retained in the GIT, with fibers and fragments being the most common. A total of 22 pieces of microplastic were identified with Nile Red staining by slide analysis. A significant difference was found between the abundance of microplastic ingested per total fish length between streams with high and LU development reaches. Therefore, in relatively small amounts, microplastic ingestion appears to be common in P. multiradiatus species, regardless of the habitat in which they are found and the diet present.

Biosecurity baseline for a sustainable development of seaweed aquaculture in Latin America

Seaweed farming worldwide has increased considerably in the last century. Latin America (LATAM) has an enormous potential to contribute within the medium/long term to global seaweed production. However, the seaweed sector is not exempted by risks (e.g. diseases and pests) overall understudied in the region, reason why biosecurity and traceability measurements may be needed to some extent. In this study, policies concerning biosecurity in seaweed aquaculture in Argentina, Brazil, Chile, Colombia, Mexico and Peru were analyzed and classified for different categories. The results suggest that most of LATAM policies tend to focus on prevention measures, especially in ecological biosecurity problems, which are included mostly in general aquaculture legislations. Contrarily, economic and environmental risks are to a lesser extent covered. Furthermore, cryptic ecological aspects associated with farming such as introduction of host for diseases or genetic pollution are often overlooked, and therefore poorly managed. Within LATAM countries, Chile has the highest specificity in seaweed-exclusive legislation, likely associated to recent problems with pests and introduction of exotic species. Overall, there is a lack of information related to biosecurity risks of seaweed aquaculture in LATAM, similar to what had happened to other globally relevant producers in the southeastern Pacific that have experienced serious biosecurity problems in the recent years. Seaweed aquaculture is relatively incipient in LATAM region, but its sustainability as well as the associated food security systems may be at risk, unless new policies make compatible seaweed production and biosecurity practices.

Environmental determinants of round goby invasion refuges at a river scale: implications for conservation of native biodiversity

Introductions of exotic invasive species are a global disturbance for natural habitats. The severity of invasions can greatly vary from local to global scales, as observed in invasion refuges, which exhibit lower-than-expected invasion intensity. In this study, we analyzed the effects of water conductivity and wetland presence on the density of the round goby ( Neogobius melanostomus) in a large-scale study (>1300 sites), spanning a 400 km stretch of the St. Lawrence River (Canada). Our results showed that round goby density was null in sites with water conductivity under 100 µS cm−1 and increased toward a probable biological optimum at 300 µS cm−1. The presence of wetlands appeared to also decrease round goby density along the conductivity continuum. Similarly, fish community diversity was maximal outside of the round goby water conductivity optimum. Hence, low water conductivity (<100 µS cm−1), in interaction with the presence of wetlands, can provide a refuge for native aquatic species, establishing a simple risk assessment tool for managers. Our results also highlighted the high value of wetland conservation for the conservation of native species biodiversity.

Genetic and Ecological Approaches to Introduced Populations of Pumpkinseed Sunfish (Lepomis gibbosus) in Southwestern Europe

Freshwater systems are among the most affected by the introduction of exotic species. The pumpkinseed sunfish Lepomis gibbosus, a centrarchid native to eastern North America, is listed among the top ten introduced freshwater fishes with the greatest ecological impact globally. Despite this, genetic and evolutionary studies of the species are still scarce. Here, we analyzed the genetic variability of introduced populations of L. gibbosus using three mitochondrial genes (COI, d-loop, and ND1). In addition, we used species distribution modeling to compare the niche of introduced versus native populations to assess the present and potential future distribution of the species under different climate change scenarios. Compared with the native populations, introduced ones present a lower level of genetic variability, indicating these populations originated from a small number of individuals from the native (Atlantic) population in the USA and Canada. The low variability was likely driven by a founder effect and subsequent bottleneck, as often occurs in invasive species. Our modeling results suggest not only that L. gibbosus modified its niche during the invasion process in Europe but also the possible global expansion of the species under future climatic conditions, which could facilitate its establishment in almost all continents.

Survey-based Analysis for Proximate Anthropogenic Driving Factors of Forest Landscape Degradation: The Case of Kilimanjaro World Heritage Site, Tanzania

Protecting tropical forests from degradation is a critical challenge for implementing institutional instruments, including the World Heritage Convention (WHC) and strategic policies for forest protection in the Global South. Identifying and addressing proximate anthropogenic causes are important steps to support the effective implementation of institutional instruments. Our study, therefore, investigated the proximate anthropogenic driving factors of forest degradation in the Kilimanjaro World Heritage Sites (WHS) to support WHC and strategic policies for forest protection and natural heritage sustainability. We used surveys of experts and residents to generate data to identify direct anthropogenic driving factors and analyze forestry and agricultural activities, the level of tourism, and bush burning/wildfire activities as proximate anthropogenic driving factors of forest degradation. Our key findings showed that direct anthropogenic factors are mostly attributed to agricultural activities, beekeeping and honey harvesting, and charcoal production. Other factors include wildfire/bush burning, illegal logging, tourism activities, infrastructural developments, and the introduction of exotic plant species. Also, the findings showed that the level of forestry activities on the site is high, and most of the people have no access to productive (community) forests. Additionally, our findings showed that the levels of agricultural activities on the site and accessibility to agricultural lands are low and very low, respectively. Furthermore, our findings showed that the level of tourism activities on the site is high, and bush burning (wildfire) on the site is attributed to tourism activities and park rangers. The study findings are crucial to support decision-making processes on implementing the WHC and other strategic policies for forest protection and natural heritage sustainability in WHS across the Global South

The role of social media groups on illegal wildlife trade in four Mexican states: A year-long assessment

Illegal wildlife trade consists of harvesting wildlife products and undertaking its trade contrary to national and international laws. It has become one of the main threats to wildlife, along with habitat loss and the introduction of exotic species. The Internet modified how illegal trade works as it increases species exposure and market venues. Although it is a critical problem in Latin America, it has received limited attention. A region worth studying is the country of Mexico, as it is a megadiverse country, has multiple commercial treaties, and is considered an active part of the wildlife trade. Thus, our objective was to determine the role of social media in illegal trade in Mexican states with different income levels. We looked for social media groups that serve as virtual marketplaces in the states of Estado de México, Guerrero, Jalisco, and Oaxaca. We comprehensively monitored the groups from January 1, 2019, until December 31, 2019. We browsed all the posts listed for sale and recorded all the available information, including the legal status of the individual. We found 175 posts in nine groups that offered 392 wildlife individuals. We registered 90 different species, of which 39 were mammals (202 individuals), 26 were birds and 23 were reptiles, with a total estimated selling value of US$ 683,967. Furthermore, we detected a significant difference between the number of individuals of mammals, birds, and reptiles sold. Our analysis indicates a large number and diversity of species being sold in social media confirming its importance as a virtual marketplace for biodiversity trade and not only for regional species.

Effects of Shading on the Growth and Photosynthetic Fluorescence Characteristics of Castanopsis hystrix Seedlings of Top Community-Building Species in Southern Subtropical China

Castanopsis hystrix is a major community-building species in the top communities of southern subtropical China, with a high natural regeneration capacity. However, excessive logging and the introduction of exotic tree species have substantially reduced the area of natural forest patches of Castanopsis hystrix, and seedling regeneration is essential for the long-term continuation of Castanopsis hystrix populations. To explore the effects of light intensity on the seedling emergence and early growth of Castanopsis hystrix, shading experiments were conducted under four shading treatments (0%, 40%, 60%, and 80%). The growth, biomass accumulation, and distribution, the quality index of seedlings, the morphology and structure of the root systems of seedlings, and the leaf chlorophyll content and chlorophyll fluorescence properties of seedlings under different shading treatments were analyzed. The results displayed the following: (1) Shade intensity impacts growth of Castanopsis hystrix seedlings and biomass allocation, with optimal results observed at 60% shade, leading to the promotion of organic matter production in leaves and the limitation of stem growth. (2) Using a multi-indicator composite index, it was determined that seedling quality for Castanopsis hystrix peaks at 60% shade intensity. (3) Shade significantly impacts the morphology and structure of Castanopsis hystrix’s root system, with most root characteristics peaking at 60% shade, indicating a substantial increase in root development compared to no-shade conditions. (4) The D-values indicated the most suitable shade intensity for seedling growth to be 60%, suggesting that Castanopsis hystrix seedlings are sensitive to light and excessive light can be detrimental to their growth. (5) The 60% shade treatment showed the maximum values of chlorophyll fluorescence characteristics and photochemical activity, with variations in energy conversion efficiency and dissipation reflected in parameters like photochemical burst coefficient (qP), photochemical burst coefficient (qN), the actual photometric yield of PSII under light acclimation (YII), and the maximum photosynthetic electron transport rate in photoinhibition (ETR), thereby supporting seedling growth and maintaining the normal function of photosynthetic organs. In conclusion, 60% shade treatment can effectively improve the growth and photosynthetic characteristics of Castanopsis hystrix seedlings and promote the accumulation of nutrient elements, ultimately promoting their growth.

Enchytraeids in imported soil and organic deposits in Pyramiden, an abandoned mining town on Spitsbergen in the High Arctic

In Arctic soils, potworms (Clitellata: Enchytraeidae) are a particularly important decomposer group. There are relatively many faunistic records from the Svalbard archipelago, in particular its main island Spitsbergen, but few ecological studies on enchytraeids. With climate change and increasing tourism, the introduction and subsequent spreading of exotic species might pose a threat to native biotic communities. In Pyramiden, a Russian (formerly Soviet) coal mining settlement on Spitsbergen abandoned in 1998, Chernozem soil from southern Russia or Ukraine had been imported in 1983 to create lawns. Today the long central lawn presents an environmental gradient: on one end rather shallow humus-rich soil is fertilized by a sea bird colony on an adjacent building, the central part has a rich organic horizon topping humus-rich mineral soil, whereas on the other end humus-rich soil is covered by deposited mineral soil. In August 2018, we sampled this gradient to study the enchytraeid assemblage. Additional samples were also taken within frames with a vigorous grass turf in front of residential houses and in a vegetated heap of decomposing organic material (mostly woodchips). The objectives were to see (1) if and how the differences between habitats would be reflected by changes of the enchytraeid assemblages and (2) if there were any potentially introduced species. Almost 3700 specimens were identified and 9 species were recorded, which is high for habitats of the High Arctic. One species, Enchytraeus buchholzi s.l., had been recorded before in the archipelago only once, also in imported soil. This small-bodied euryoecious r-strategist is abundant in agricultural and other disturbed soils. Molecular barcoding and comparison with sequences from Central Europe showed close resemblance to several specimens, which makes an introduction with the transferred Chernozem highly probable. Most enchytraeids were concentrated in the upper 3 cm of soil (even if mineral), only in the organic deposits vertical distribution was rather even down to 12 cm depth. Numbers in the organic deposits were exceedingly high (ca 417,000 individuals/m2) and E. buchholzi s.l. represented ca 90 % of all specimens. Ordination (NMDS) showed all habitats to host rather distinct assemblages. Spearman's rank correlation showed significant positive correlation of species richness with conductivity and total nitrogen and of abundance with phosphorous and potassium contents in aqueous solution.

Future forests and biodiversity: Effects of Douglas fir introduction into temperate beech forests on plant diversity

Introduction of drought-tolerant exotic tree species is seen as an important adaptation measure of forest management to climate change in Central Europe. Douglas fir (Pseudotsuga menziesii) is particularly favored in this context, because it is adapted to summer droughts due to the climate in its natural distribution range in temperate western North America and it is also fast-growing and the wood is readily marketable. In Germany, there are plans to grow Douglas fir on a large scale in mixed forests with other tree species on acidic soils. Potential ecological consequences have not yet been sufficiently scrutinized. Here, we analyze effects of Douglas fir introduction into forests of European beech (Fagus sylvatica), which would naturally predominate Central Europe’s forests. We analyzed vascular plant diversity and species composition of the ground vegetation in a gradient with increasing Douglas fir canopy fraction that ranged from pure beech (0% Douglas fir) via mixed stands (25%, 50%, 75% Douglas fir) to pure (100%) Douglas fir forest. Species richness, Shannon diversity, and Simpson diversity increased with increasing Douglas fir canopy fraction. However, this increase was primarily driven by an increase of nitrogen-tolerant disturbance indicators, whereas the share of forest species that were predominant in pure beech forests decreased. Beech forest species declined gradually with increasing Douglas fir canopy fraction, but these declining species were fewer than the number of species increasing due to Douglas fir introduction. Cover of ∼30% of species remained constant when Douglas fir was introduced. Strong changes in the ground vegetation were observed at Douglas fir canopy fractions > 40 – 50% and the original character of the ground vegetation was completely lost beyond a threshold of 75%. Therefore, we discourage from high Douglas fir proportions beyond these thresholds in production forests and from any introduction of Douglas fir where nature conservation is a priority.

Using network analysis to study and manage human-mediated dispersal of exotic species

Human-mediated dispersal is a major contributor of biological invasions. To reduce impacts induced by the introduction and spread of exotic species, biosecurity interventions are put into place. These interventions often rely on risk-assessment procedures, whereby biosecurity practitioners (which includes researchers, stakeholders such as national park managers, and all other decision makers who determine when and how to protect biodiversity) attempt to preemptively identify and predict which exotic species could potentially become a threat to natural ecosystems. In theory, extensive field and experimental studies would be required to accurately and precisely determine the risks of biological invasion of a species or group of species. However, due to a lack of resources or knowledge, such critical studies are limited. As a result, biosecurity practitioners rarely have a full picture of the extent to which the exotic species has and will spread at the time of decision making. Hence, they instead opt for preventive measures such as identifying and managing potential target exotic species which are likely to be invasive or dispersal pathways through which exotic species are likely to be introduced and spread. As most of the uncertainties pertaining to biosecurity interventions lie in the resolution of data made available to practitioners at the time of decision making, we first present some of the different types of information which are readily available during the risk-assessment procedure. We then highlight how one could exploit these different resolutions of data during the risk-assessment procedure using network analysis to better understand human-mediated dispersal of exotic species. By doing so, our paper puts forward what network analysis has to offer practitioners in the context of biosecurity interventions.

Trait-independent habitat associations explain low co-occurrence in native and exotic birds on a tropical volcanic island.

On oceanic islands, strong human impacts on habitats, combined with introductions of exotic species, modify the composition of terrestrial bird assemblages and threaten their ecological functions. In La Réunion, an oceanic island located in the Madagascan region, a national park was established in 2007 to counter the ecosystem-level effects of three centuries of habitat conversion, native species destruction and exotic species introductions. Here, we investigated how bird assemblages were structured in these human-modified landscapes, 10 years before the national park set out its first conservation measures. We used a combination of multivariate statistics and generalized additive models to describe variations in the taxonomic and functional composition and diversity of 372 local bird assemblages, encompassing 20 species, along gradients of habitat composition and configuration. We found that native species were tied to native habitats while exotic species were associated with urban areas and man-modified landscape mosaics, with some overlap at mid-elevations. Species' trophic preferences were segregated along habitat gradients, but ecological traits had an overall weak role in explaining the composition of species assemblages. Hence, at the time of the survey, native and exotic species in La Réunion formed two spatially distinct species assemblages with contrasting ecological trait suites that benefited from antagonistic habitat compositions and dynamics. We conclude that our results support the analysis of historical data sets to establish reference points to monitor human impacts on insular ecosystems.