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Understanding the likely future impacts of biological invasions is crucial yet highly challenging given the multiple relevant environmental, socio-economic and societal contexts and drivers. In the absence of quantitative models, methods based on expert knowledge are the best option for assessing future invasion trajectories. Here, we present an expert assessment of the drivers of potential alien species impacts under contrasting scenarios and socioecological contexts through the mid-21st century. Based on responses from 36 experts in biological invasions, moderate (20%-30%) increases in invasions, compared to the current conditions, are expected to cause major impacts on biodiversity in most socioecological contexts. Three main drivers of biological invasions-transport, climate change and socio-economic change-were predicted to significantly affect future impacts of alien species on biodiversity even under a best-case scenario. Other drivers (e.g. human demography and migration in tropical and subtropical regions) were also of high importance in specific global contexts (e.g. for individual taxonomic groups or biomes). We show that some best-case scenarios can substantially reduce potential future impacts of biological invasions. However, rapid and comprehensive actions are necessary to use this potential and achieve the goals of the Post-2020 Framework of the Convention on Biological Diversity.

A branch of island biogeography has emerged to explain alien species diversity in the light of the biogeographic and anthropogenic context, yet overlooking the functional and phylogenetic facets. Evaluating alien and native birds of 407 oceanic islands worldwide, we built structural equation models to assess the direct and indirect influence of biotic, geographic, and anthropogenic contexts on alien functional diversity (FD) and phylogenetic diversity (PD). We found that alien taxonomic richness was the main predictor of both diversities. Anthropogenic factors, including colonization pressure, associated with classic biogeographical variables also strongly influenced alien FD and PD. Specifically, habitat modification and human connectivity markedly drove alien FD, especially when controlled by taxonomic richness, whereas the human population size, gross domestic product, and native PD were crucial at explaining alien PD. Our findings suggest that humans not only shape taxonomic richness but also other facets of alien diversity in a complex way. [ABSTRACT FROM AUTHOR]

Shifts between native and alien climatic niches pose a major challenge for predicting biological invasions. This is particularly true for insular species because geophysical barriers could constrain the realization of their fundamental niches, which may lead to underestimates of their invasion potential. To investigate this idea, we estimated the frequency of shifts between native and alien climatic niches and the magnitude of climatic mismatches using 80,148 alien occurrences of 46 endemic insular amphibian, reptile, and bird species. Then, we assessed the influence of nine potential predictors on climatic mismatches across taxa, based on species' characteristics, native range physical characteristics, and alien range properties. We found that climatic mismatch is common during invasions of endemic insular birds and reptiles: 78.3% and 55.1% of their respective alien records occurred outside of the environmental space of species' native climatic niche. In comparison, climatic mismatch was evident for only 16.2% of the amphibian invasions analyzed. Several predictors significantly explained climatic mismatch, and these varied among taxonomic groups. For amphibians, only native range size was associated with climatic mismatch. For reptiles, the magnitude of climatic mismatch was higher for species with narrow native altitudinal ranges, occurring in topographically complex or less remote islands, as well as for species with larger distances between their native and alien ranges. For birds, climatic mismatch was significantly larger for invasions on continents with higher phylogenetic diversity of the recipient community, and when the invader was more evolutionarily distinct. Our findings highlight that apparently common niche shifts of insular species may jeopardize our ability to forecast their potential invasions using correlative methods based on climatic variables. Also, we show which factors provide additional insights on the actual invasion potential of insular endemic amphibians, reptiles, and birds. [ABSTRACT FROM AUTHOR]

Biological invasions are a global challenge that has received insufficient attention. Recently available cost syntheses have provided policy- and decision makers with reliable and up-to-date information on the economic impacts of biological invasions, aiming to motivate effective management. The resultant InvaCost database is now publicly and freely accessible and enables rapid extraction of monetary cost information. This has facilitated knowledge sharing, developed a more integrated and multidisciplinary network of researchers, and forged multidisciplinary collaborations among diverse organizations and stakeholders. Over 50 scientific publications so far have used the database and have provided detailed assessments of invasion costs across geographic, taxonomic, and spatiotemporal scales. These studies have provided important information that can guide future policy and legislative decisions on the management of biological invasions while simultaneously attracting public and media attention. We provide an overview of the improved availability, reliability, standardization, and defragmentation of monetary costs; discuss how this has enhanced invasion science as a discipline; and outline directions for future development. [ABSTRACT FROM AUTHOR]

Background: Biological invasions threaten the functioning of ecosystems, biodiversity, and human well-being by degrading ecosystem services and eliciting massive economic costs. The European Union has historically been a hub for cultural development and global trade, and thus, has extensive opportunities for the introduction and spread of alien species. While reported costs of biological invasions to some member states have been recently assessed, ongoing knowledge gaps in taxonomic and spatio-temporal data suggest that these costs were considerably underestimated. Results: We used the latest available cost data in InvaCost (v4.1)—the most comprehensive database on the costs of biological invasions—to assess the magnitude of this underestimation within the European Union via projections of current and future invasion costs. We used macroeconomic scaling and temporal modelling approaches to project available cost information over gaps in taxa, space, and time, thereby producing a more complete estimate for the European Union economy. We identified that only 259 out of 13,331 (~ 1%) known invasive alien species have reported costs in the European Union. Using a conservative subset of highly reliable, observed, country-level cost entries from 49 species (totalling US$4.7 billion; 2017 value), combined with the establishment data of alien species within European Union member states, we projected unreported cost data for all member states. Conclusions: Our corrected estimate of observed costs was potentially 501% higher (US$28.0 billion) than currently recorded. Using future projections of current estimates, we also identified a substantial increase in costs and costly species (US$148.2 billion) by 2040. We urge that cost reporting be improved to clarify the economic impacts of greatest concern, concomitant with coordinated international action to prevent and mitigate the impacts of invasive alien species in the European Union and globally. [ABSTRACT FROM AUTHOR]

The Emergency Recovery Plan for freshwater biodiversity recognizes that addressing nonnative species is one of six principal actions needed to bend the curve in freshwater biodiversity loss. This is because introduction rates of nonnative species continue to accelerate globally and where these species develop invasive populations, they can have severe impacts on freshwater biodiversity. The most effective management measure to protect freshwater biodiversity is to prevent introductions of nonnative species. Should a nonnative species be introduced, however, then its early detection and the implementation of rapid reaction measures can avoid it establishing and dispersing. If these measures are unsuccessful and the species becomes invasive, then control and containment measures can minimize its further spread and impact. Minimizing further spread and impact includes control methods to reduce invader abundance and containment methods such as screening of invaded sites and strict biosecurity to avoid the invader dispersing to neighbouring basins. These management actions have benefitted from developments in invasion risk assessment that can prioritize species according to their invasion risk and, for species already invasive, ensure that management actions are commensurate with assessed risk. The successful management of freshwater nonnative species still requires the overcoming of some implementation challenges, including nonnative species often being a symptom of degraded habitats rather than the main driver of ecological change, and eradication methods often being nonspecies specific. Given the multiple anthropogenic stressors in freshwaters, nonnative species management must work with other restoration strategies if it is to deliver the Emergency Recovery Plan for freshwater biodiversity. [ABSTRACT FROM AUTHOR]

Anthropogenic biological invasions represent major concerns but enable us to investigate rapid evolutionary changes and adaptation to novel environments. The goldfish Carassius auratus with sexual diploids and unisexual triploids coexisting in natural waters is one of the most widespread invasive fishes in Tibet, providing an ideal model to study evolutionary processes during invasion in different reproductive forms from the same vertebrate. Here, using whole‐genome resequencing data of 151 C. auratus individuals from invasive and native ranges, we found different patterns of genomic responses between diploid and triploid populations during their invasion of Tibet. For diploids, although invasive individuals derived from two different genetically distinct sources had a relative higher diversity (π) at the population level, their individual genetic diversity (genome‐wide observed heterozygosity) was significantly lower (21.4%) than that of source individuals. Population structure analysis revealed that the invasive individuals formed a specific genetic cluster distinct from the source populations. Runs of homozygosity analysis showed low inbreeding only in invasive individuals, and only the invasive population experienced a recent decline in effective population size reflecting founder events. For triploids, however, invasive populations showed no loss of individual genetic diversity and no genetic differentiation relative to source populations. Regions of putative selective sweeps between invasive and source populations of diploids mainly involved genes associated with mannosidase activity and embryo development. Our results suggest that invasive diploids deriving from distinct sources still lost individual genetic diversity resulting from recent inbreeding and founder events and selective sweeps, and invasive triploids experienced no change in genetic diversity owing to their reproduction mode of gynogenesis that precludes inbreeding and founder effects and may make them more powerful invaders. [ABSTRACT FROM AUTHOR]

Species distribution models (SDMs) have been widely applied to predict geographic ranges of species across space and time under the assumption of niche conservatism (i.e., species niches change very slowly). However, an increasing number of studies have reported evidence of rapid niche changes across space and time, which has sparked a widespread debate on whether SDMs can be transferred to new areas or time periods. Understanding how niche changes affect SDM transferability is thus crucial for the future application and improvement of SDMs. Biological invasions provide an opportunity to address this question due to the geographically independent distributions and diverse patterns of niche changes between species' native and introduced ranges. Here, we synthesized findings on 217 species from 50 studies to elucidate the effects of niche change on the spatial transferability of SDMs. When niche change was considered as a categorical classification (conserved vs. shifted niches) in tests of the niche conservatism hypothesis, SDM transferability was markedly lower for species with a shifted niche in their introduced range. When niche change was measured as numerical dynamics between native and introduced niches, SDM transferability was high for species occupying similar environmental conditions in both ranges and low for species with more environmental space remaining unoccupied in the introduced range. Surprisingly, the number of presence points used for developing SDMs turned out to have an even stronger effect on transferability. Our results thus reveal detrimental effects of both niche change and lack of presence points on SDM transferability. It is necessary to consider both niche change and data quality for improving the transferability of SDMs, so that they can better support conservation management and policy decisions. [ABSTRACT FROM AUTHOR]

The reliability of transferring species distribution models (SDMs) to new ranges and future climates has been widely debated. Biological invasions offer the unique opportunity to evaluate model transferability, as distribution data between species' native and introduced ranges are geographically independent of each other. Here, we performed the first global quantitative synthesis of the spatial transferability of SDMs for 235 invasive species and assessed the association of model transferability with the focal invader, model choice and parameterisation. We found that SDMs had limited spatial transferability overall. However, model transferability was higher for terrestrial endotherms, species introduced from or to the Southern Hemisphere, and species introduced more recently. Model transferability was also positively associated with the number of presences for model calibration and evaluation, respectively, but negatively with the number of predictors. These findings highlight the importance of considering the characteristics of the focal invader, environment and modelling in the application and assessment of SDMs. [ABSTRACT FROM AUTHOR]

Biological invasions are a primary threat to global biodiversity, supporting mounting calls for the development of early‐warning systems to manage existing and emerging invaders. Here, we evaluated the geographical pattern of invasion risks of currently established and potentially emerging nonnative freshwater fishes in China by jointly considering the threats of introduction and establishment under climate change. Introduction threats were estimated according to proxies of human activities and propagule pressure for two primary pathways (aquaculture or ornamental). Establishment threats for 51 current and 64 potential invaders (based on whether having established or not self‐sustaining populations) were assessed using an ensemble of species distribution models under current (1960–1990) and future [2041–2060 (2050s) and 2061–2080 (2070s)] climate scenarios. Geographical patterns of invasion risk were then assessed by overlaying the threats of introduction and establishment for each species group both in present‐day and in the future. We found that eastern China displayed the highest threat of introduction. By contrast, southeastern and northwestern regions were identified as the most suitable for the establishment of both current and potential invaders. Under a changing climate, 83 out of 115 species displayed an increase in habitat suitability, resulting in an overall increase of 4.8% by 2050s and 7.1% by 2070s in the extent of suitable habitat for nonnative freshwater fishes. Taken together, invasion risk was found to be highest in southeastern China and lowest in the Tibet Plateau. Our research highlights the importance of assessing invasion risk by integrating the threats associated with the introduction and establishment stages. In particular, our findings revealed convergent patterns of invasion risk between current and potential nonnative freshwater fishes under climate change. Geographic patterns in hotspots of existing and emerging invasions provide critical insights to guide the allocation of resources to monitor and control existing and emerging invasions in China. [ABSTRACT FROM AUTHOR]

Aim Human-mediated species introductions and extirpations have resulted in the homogenization of biotas over time. However, there remains considerable uncertainty in our understanding of homogenization process for megadiverse regions of the world. Here, we investigate the consequences of widespread species invasions and extirpations for the biogeography of China's unique freshwater fish fauna. Location China. Methods By assembling a comprehensive dataset for distribution of Chinese freshwater fishes, we quantify how non-native fish species, from both overseas introductions and domestic translocations, has led to taxonomic homogenization of fish faunas at watershed, basin, ecoregion and country scales. We explore how the observed patterns in homogenization vary geographically, and identify those species most responsible for the faunal changes. Lastly, we simulate how China's fish fauna may continue to homogenize according to different scenarios of anticipated species introductions and extirpations. Results We demonstrate that species introductions and extirpations have homogenized freshwater fish faunas across China. Overall compositional similarity of watersheds increased by 7.0% (from a historical 14.9% to 21.9% in the present day; Sørensen index). Compositional similarity of 96 of 103 (93.2%) watersheds increased, with western basins exhibiting the highest magnitude. Translocated non-native species associated with aquaculture practices contributed the most to faunal homogenization when compared to alien species (7.3% and 0.4%, respectively). Furthermore, faunal homogenization is predicted to intensify an additional 0.5-4.2% with increasing numbers of new non-native species introductions and the extirpation of native species. Main conclusions Species introductions and extirpations have resulted in the significant impoverishment, and thus the loss of antiquity, of China's freshwater fish fauna over the past century. In the light of the growing realization that species composition (not richness) defines the role that biodiversity plays in maintaining ecosystem function, our study highlights the need for conservation strategies in China that consider changing patterns of β diversity. [ABSTRACT FROM AUTHOR]

GoldfishCarassius auratushave been established in myriad ecosystems outside of their native ranges, and part of their successful establishment in new ecosystems might be attributed to the shift in life history traits. To explore the role of phenotypic shifts in Goldfish invasions, we quantified and compared spawning times and growth rates in the early life history of nonnative Goldfish from Chabalang and Chongdui wetlands in the Yarlung Tsangpo River basin. Spawning of nonnative Goldfish began on March 20 and April 14 for the Chabalang and the Chongdui populations, respectively, and both were considerably earlier than native populations despite the cold environments in the Yarlung Tsangpo River basin. Growth rates for the Chabalang population were significantly higher than those for the Chongdui population during the first 14 d posthatch; however, growth rates for the Chongdui population became higher after the 37th day. Within the Chabalang population, Goldfish hatching later had faster growth rates than individuals hatching earlier. Consequently, it seems that shifts in the timing of spawning and growth rates play an important role in the invasion success of Goldfish in extremely cold climates. Received January 9, 2014; accepted December 1, 2014 [ABSTRACT FROM PUBLISHER]

The South China Sea (SCS) sustains and is a regional center of high marine and coastal biodiversity. It is also one of the most important mariculture and marine fisheries regions in the world. Many non-indigenous species (NIS) were introduced into the SCS as artifacts of increasing mariculture production and fishery harvests. Little information exists about NIS in the SCS. In this study, research examining NIS and their threats in the SCS are reviewed. Current NIS conditions assessed include their status, threat to native biodiversity, contribution to mariculture and fisheries harvest, management, and the need for future research in specific areas are identified. A total of 90 NIS including 17 algae, 6 vascular plants, 3 bryozoans, 23 molluscs, 6 crustacea, 3 ascidians, and 32 fishes were introduced into the SCS from 1600 to the present. The primary pathways of introduction are through aquaculture, followed by shipping, ecological restoration, and biocontrol. The main introduced country is China. Some NIS have caused negative impacts on the environment and economy. Some NIS are potential threats to humans as well as biodiversity in the SCS. More research focused upon monitoring and managing NIS in the SCS is needed. Unlabelled Image • We reviewed the literature and all other information about non-indigenous species in the South China Sea. • The fish and molluscs are the taxonomic groups with the greatest number of recorded non-indigenous species. • Aquaculture is the primary pathway of introduction for non-indigenous species in the South China Sea. • More research and international cooperation is needed in future studies of non-indigenous species in the South China Sea. [ABSTRACT FROM AUTHOR]