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Future dynamics of biological invasions are highly uncertain because they depend on multiple social–ecological drivers. We used a scenario‐based approach to explore potential management options for invasive species in Europe. During two workshops involving a multidisciplinary team of experts, we developed a management strategy arranged into 19 goals relating to policy, research, public awareness, and biosecurity. We conceived solutions for achieving these goals under different plausible future scenarios, and identified four interrelated recommendations around which any long‐term strategy for managing invasive species can be structured: (1) a European biosecurity regime, (2) a dedicated communication strategy, (3) data standardization and management tools, and (4) a monitoring and assessment system. Finally, we assessed the feasibility of the management strategy and found substantial differences among scenarios. Collectively, our results indicate that it is time for a new strategy for managing biological invasions in Europe, one that is based on a more integrative approach across socioeconomic sectors and countries. [ABSTRACT FROM AUTHOR]

The Asian hornet (Vespa velutina) has rapidly become a source of stress for the beekeeping sector. Several methods have been developed to control its impact and spread, though some of these impose a high risk for native insects. Among these methods are electric harps, which are physical barriers that electrocute hornets pass through two wires powered by a current generator. Here we evaluated the selectiveness and risk of damage for local entomofauna of the electric harps in a study carried out over three years and four locations in Girona province (NE Catalonia, Spain). The electric harps showed a high selectiveness, with 90.5% of all insects trapped (3331 individuals) catalogued as Asian hornets, although this greatly varied over years and locations with values ranging from 29.9 to 94.3%. The risk of damage to electric harps for local entomofauna was very low in all surveyed areas and years. Native insects, excluding domestic honey bees, accounted for, as a mean, 1.2% of all insects trapped over the study period (range 0–2.4%). Our results suggest that electric harps might be a useful environmentally-friendly method aiming to reduce predation pressure of the Asian hornet at beehives. [ABSTRACT FROM AUTHOR]

The extent and impacts of biological invasions on biodiversity are largely shaped by an array of socio-economic and environmental factors, which exhibit high variation among countries. Yet, a global analysis of how these factors vary across countries is currently lacking. Here, we investigate how five broad, country-specific socio-economic and environmental indices (Governance, Trade, Environmental Performance, Lifestyle and Education, Innovation) explain country-level (1) established alien species (EAS) richness of eight taxonomic groups, and (2) proactive or reactive capacity to prevent and manage biological invasions and their impacts. These indices underpin many aspects of the invasion process, including the introduction, establishment, spread and management of alien species. They are also general enough to enable a global comparison across countries, and are therefore essential for defining future scenarios for biological invasions. Models including Trade, Governance, Lifestyle and Education, or a combination of these, best explained EAS richness across taxonomic groups and national proactive or reactive capacity. Historical (1996 or averaged over 1996–2015) levels of Governance and Trade better explained both EAS richness and the capacity of countries to manage invasions than more recent (2015) levels, revealing a historical legacy with important implications for the future of biological invasions. Using Governance and Trade to define a two-dimensional socio-economic space in which the position of a country captures its capacity to address issues of biological invasions, we identified four main clusters of countries in 2015. Most countries had an increase in Trade over the past 25 years, but trajectories were more geographically heterogeneous for Governance. Declines in levels of Governance are concerning as they may be responsible for larger levels of invasions in the future. By identifying the factors influencing EAS richness and the regions most susceptible to changes in these factors, our results provide novel insights to integrate biological invasions into scenarios of biodiversity change to better inform decision-making for policy and the management of biological invasions. [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]

Scenario analysis has emerged as a key tool to analyze complex and uncertain future socio-ecological developments. However, currently existing global scenarios (narratives of how the world may develop) have neglected biological invasions, a major threat to biodiversity and the economy. Here, we use a novel participatory process to develop a diverse set of global biological invasion scenarios spanning a wide range of plausible global futures through to 2050. We adapted the widely used "two axes" scenario analysis approach to develop four families of four scenarios each, resulting in 16 scenarios that were later clustered into four contrasting sets of futures. Our analysis highlights that socioeconomic developments and technological innovation have the potential to shape biological invasions, in addition to well-known drivers, such as climate and human land use change and global trade. Our scenarios partially align with the shared socioeconomic pathways created by the climate change research community. Several factors that drive differences in biological invasions were underrepresented in the shared socioeconomic pathways; in particular, the implementation of biosecurity policies. We argue that including factors related to public environmental awareness and technological and trade development in global scenarios and models is essential to adequately consider biological invasions in global environmental assessments and thereby obtain a more integrative picture of future social–ecological developments. [ABSTRACT FROM AUTHOR]

AlienScenarios, a three-year project starting in March 2019, will evaluate for the first time the range of plausible futures of biological invasions for the 21st century. AlienScenarios consists of seven project partners and seven integrated complementary subprojects. We will develop the qualitative narratives for plausible futures of global alien species richness and impacts in the 21st century - the Alien Species Narratives (ASNs). The ASNs further serve as overarching concept to parameterize quantitative models of global, continental and regional futures of biological invasions. We will also establish the first global mechanistic invasion model considering major processes of biological invasions such as source pools, driver dynamics and establishment rates. Further, we will assess the impacts of invasive alien species (IAS) in terms of economic costs according to the different ASNs. In addition, we will assess the consequences of different levels of implementation of the European Union Regulation on IAS. Providing some more detailed regional information, we will analyse changes of the functional composition of communities in mountain regions under different scenario storylines and will extend the analyses to the Global South using Panama as a country-level case study. Finally, the results of the other WPs will be synthesized, and the approach and results of AlienScenarios will be discussed with and communicated to stakeholders and the wider community. AlienScenarios will provide crucially needed insights for pro-active alien species management and policy. It will thus make an important contribution to global assessments and projections of biodiversity and ecosystem services, as well as regional policies (e.g. EU regulation on IAS). [ABSTRACT FROM AUTHOR]

AlienScenarios, a three-year project starting in March 2019, will evaluate for the first time the range of plausible futures of biological invasions for the 21st century. AlienScenarios consists of seven project partners and seven integrated complementary subprojects. We will develop the qualitative narratives for plausible futures of global alien species richness and impacts in the 21st century -- the Alien Species Narratives (ASNs). The ASNs further serve as overarching concept to parameterize quantitative models of global, continental and regional futures of biological invasions. We will also establish the first global mechanistic invasion model considering major processes of biological invasions such as source pools, driver dynamics and establishment rates. Further, we will assess the impacts of invasive alien species (IAS) in terms of economic costs according to the different ASNs. In addition, we will assess the consequences of different levels of implementation of the European Union Regulation on IAS. Providing some more detailed regional information, we will analyse changes of the functional composition of communities in mountain regions under different scenario storylines and will extend the analyses to the Global South using Panama as a country-level case study. Finally, the results of the other WPs will be synthesized, and the approach and results of AlienScenarios will be discussed with and communicated to stakeholders and the wider community. AlienScenarios will provide crucially needed insights for pro-active alien species management and policy. It will thus make an important contribution to global assessments and projections of biodiversity and ecosystem services, as well as regional policies (e.g. EU regulation on IAS). [ABSTRACT FROM AUTHOR]

Aim: The establishment and spread of invasive alien species may be influenced by several mutually interacting factors, whose understanding is paramount to develop effective biosecurity policies. However, studies focused on modelling spatially explicit patterns of future invasion risk have so far focused on species response to climate change impacts, while land‐use change has been neglected. We investigated how the interplay between climate and land‐use change could affect the future potential distribution and dispersal corridors of four alien squirrels introduced to Europe (Sciurus carolinensis,Callosciurus finlaysonii, Callosciurus erythraeus and Eutamias sibiricus). Location and Methods: Our study was conducted in Italy. We used Species Distribution Models and circuit theory methods to test whether future scenarios based only on climate change predict a different effect on range and connectivity of alien squirrel populations, compared to scenarios that include both climate and land‐use changes. Results: Scenarios based only on climate change predicted a range increase and a high geographic stability (>50%) for most species, with different, yet limited, effects on connectivity corridors. Conversely, scenarios based on both climate and land‐use change showed a loss in range extent and a low geographic stability (<50%) of both range and dispersal corridors for most species. Main conclusions: Scenarios considering both climate and land‐use change provide predictions on invasion risk that overturn those including only climate change. The effect of global warming alone would lead to a considerable range expansion of all species. Conversely, when land‐use change is added, a potential loss in suitable habitat and dispersal corridors is predicted for alien squirrels, hence limiting their range expansion. We recommend using multiple drivers in models to obtain reliable predictions for implementing biosecurity policies related to invasive alien species. [ABSTRACT FROM AUTHOR]

Aim To examine the relationship between island characteristics (area, distance to the nearest continent, climate and human population size) and ant species richness, as well as the factors underlying global geographical clustering of native and exotic ant composition on islands. Location One hundred and two islands from 20 island groups around the world. Methods We used spatial linear models that consider the spatial structure of islands to examine patterns of ant species richness. We also performed modularity analyses to identify clusters of islands hosting a similar suite of species and constructed conditional inference trees to assess the characteristics of islands that explain the formation of these island-ant groups. Results Island area was the best predictor of ant species richness. However, distance to the nearest continent was an important predictor of native ant species richness, as was human population size for exotic species richness. Native species appear slightly more modulated (i.e. well grouped in species assemblages that are present over a distinct cluster of islands) than are exotic species. Exotic species, while still exhibiting some modularity, tended to be widely distributed among island groups. Interestingly, ocean currents accounted for most of the variation in modularity and thus species composition for both native and exotic ant species. Main conclusions Contrary to previous work, both native and exotic species appeared to be confined to particular island regions, and patterns in the distribution of both native and exotic species were limited by a similar suite of factors. However, the distribution of exotic ant species appeared to be more influenced by human-related variables and less structured relative to those of native ant species, perhaps due to the long-term (and increasing) influence of human-mediated dispersal that favours exotic species. [ABSTRACT FROM AUTHOR]

Aim: Understanding the role of enemy release in biological invasions requires an assessment of the invader's home range, the number of invasion events and enemy prevalence. The common wasp (Vespula vulgaris) is a widespread invader. We sought to determine the Eurasian origin of this wasp and examined world-wide populations for microsporidian pathogen infections to investigate enemy release. Location: Argentina, Eurasia, New Zealand. Methods: A haplotype network and phylogenetic tree were constructed from combined wasp COI and cytb mitochondrial markers. A morphometric study using canonical discriminant analysis was conducted on wing venation patterns. Microsporidian pathogens prevalence was also examined using small subunit rRNA microsporidia-specific primers. Results: Our spatially structured haplotype network from the native range suggested a longitudinal cline of wasp haplotypes along an east to west gradient. Six haplotypes were detected from New Zealand, and two from Argentina. The populations from the introduced range were genetically similar to the western European, United Kingdom and Ireland. The morphometric analysis showed significant morphological variation between countries and supported the Western European origin for New Zealand populations, although not for Argentine samples. Microsporidian infection rates were highest in New Zealand samples (54%), but no significant differences in infection rates were observed between the invaded and native range. Nosema species included matches to N. apis (a pathogen from honey bees) and N. bombi (from bumble bees). Main conclusions: Multiple introductions of the common wasp have occurred in the invaded range. A high microsporidian infection rate within the native range, combined with multiple introductions and a reservoir of pathogens in other social insects such as bees, likely contributes to the high microsporidian infection rates in the invaded range. Enemy release is likely to be more frequent when pathogens are rare in the home range, or are host specific and rare in reservoir populations of the introduced range. [ABSTRACT FROM AUTHOR]

Aim Understanding the conditions that promote biological invasions is a critical step to developing successful management strategies. However, the level of invasion is affected by complex interactions among environmental factors that might change across habitats and regions making broad generalizations uninformative for management. We aimed to quantify the context-dependent association of climate and human activity at landscape scale (i.e. disturbance and propagule pressure) with the level of plant invasion at local scale across different stages of invasion, habitat types and bioclimatic regions. Location Mainland Spain. Methods Based on an extensive database of vegetation plots (~50,000), we used hierarchical Bayesian models to test how climate and human activity at a landscape scale (i.e. land-cover variables) are associated with establishment (i.e. presence) and dominance (i.e. relative species richness and abundance in invaded plots) of non-native plants across nine habitat types and three bioclimatic regions. Results The association of climate with establishment and dominance of non-native plants varied depending on habitat type but not bioclimatic region. These associations also varied depending on the stage of invasion under consideration. Establishment of non-native species was more likely close to the coast, while their dominance increased in wet and warm continental areas. Human activity variables were associated with establishment and dominance similarly across bioclimatic regions. Non-native species establishment and abundance peaked in human-altered landscapes. Different habitats showed different susceptibilities to establishment versus dominance by non-native species (e.g. woodlands had medium levels of establishment, but very low dominance). Main conclusions This study highlights how complex interactions among climate, human activity and habitats can determine patterns of invasions across broad landscapes. Successful management of plant invasions will depend on understanding these context-dependent effects across habitats at the different stages of the invasion process. [ABSTRACT FROM AUTHOR]

Aim Decision-support models have considerable potential for guiding management strategies when problems are complex. The robustness of such decision-making processes is rarely evaluated, and the influence of decision criteria (or factors) in management decisions is seldom considered. We present a framework for a spatially-explicit sensitivity analysis by using a scheme developed to provide objective guidelines, in the form of static priority maps, for managing woody invasive alien plants (IAPs). Location The Cape Floristic Region, South Africa. Methods The model included seven factors related to management history, fire risk, and the age, identity, density and spread of IAPs. Each factor had a weight associated that reflected its relative importance in prioritizing areas for clearing. We changed these factor weights using three approaches of sensitivity analysis and assessed the effect of these changes on the spatial structure of the resulting priority maps in three different management regions. Results Different outcomes arose depending on the importance given to different factors. Priority maps were most sensitive to the fire-related factors, suggesting that fire is both a crucial driver of invasion in fynbos and an overriding determinant of management options. The factor ‘area burnt recently’ provided crucial information for the effective clearing of IAPs. The sensitivity of the model to changes in other factors was more context specific: levels of sensitivity were highly dependent on different features of the landscape, especially the spatial heterogeneity of particular factors. Main conclusions By clarifying the importance of factors in shaping priority maps, the sensitivity analysis framework enabled us to identify the necessary factors to produce outcomes matching a pre-selected management strategy. This is important for cost-efficient management, as acquisition and curation of data is expensive. This spatially-explicit sensitivity analysis is, thus, recommended to evaluate the robustness and generality of selected management strategies, and validate the assumptions derived from decision-making protocols. [ABSTRACT FROM AUTHOR]

Determining the geographical range of invasive species is an important component of formulating effective management strategies. In the absence of detailed distributional data, species distribution models can provide estimates of an invasion range and increase our understanding of the ecological processes acting at various spatial scales. We used two complementary approaches to evaluate the influence of historical and environmental factors in shaping the distribution of the Argentine ant ( Linepithema humile), a widespread, highly invasive species native to South America. Occurrence data were combined with environmental data at incremental spatial scales (extent and resolution) to predict the suitable range of the ant invasion using ecological niche models. In addition, we also used a spread model that simulated the jump dispersal of the species to identify the most plausible scenarios of arrival of L. humile in the NE Iberian Peninsula at local scales. Based on the results of both modelling practices, we suggest that L. humile might have reached its maximum geographic range at regional scales in the NE Iberian Peninsula. However, the species does not appear in equilibrium with the environment at small spatial scales, and further expansions are expected along coastal and inland localities of the Costa Brava. Long-distance jumps are ultimately responsible for the spread of the Argentine ant in the area. Overall, our study shows the utility of combining niche based models with spread models to understand the dynamics of species' invasions. [ABSTRACT FROM AUTHOR]

Abstract: To address the lack of physiological approaches in current models assessing the potential distribution of the Argentine ant, we used data on brood development from distinct sources to evaluate a series of degree-day models for Catalonia (NE Iberian Peninsula), and data on the brood survival and oviposition rates to develop a worker production model. The degree-day model generated using data from Newell and Barber (1913) and Benois (1973) indicated that the number of degree-days required for the complete development from egg to adult worker was 445.4 degree-days above a threshold of 15.9 °C, while the model calibrated using data from Abril et al. (2008, in press) suggested 599.5 degree-days above 18.4 °C. Comparisons between the degree-day model predictions and the currently known distribution of the Argentine ant suggested that the one generated using data from Newell and Barber (1913) and Benois (1973) overestimated the presence of the species, while the one calibrated using data from Abril et al. (2008; in press) underestimated it. On the other hand, the predicted daily net production of Argentine ant workers generated by the worker production model predicted more accurately the distribution of the Argentine ant than the degree-day models. Our results show the utility of incorporating physiological data in models to assess the distribution limits of the Argentine ant, which up to date have taken little account of the physiological needs of the species in terms of its establishment and dispersion in its introduced ranges. [Copyright &y& Elsevier]

Assessing climatic suitability provides a good preliminary estimate of the invasive potential of a species to inform risk assessment. We examined two approaches for bioclimatic modeling for 67 reptile and amphibian species introduced to California and Florida. First, we modeled the worldwide distribution of the biomes found in the introduced range to highlight similar areas worldwide from which invaders might arise. Second, we modeled potentially suitable environments for species based on climatic factors in their native ranges, using three sources of distribution data. Performance of the three datasets and both approaches were compared for each species. Climate match was positively correlated with species establishment success (maximum predicted suitability in the introduced range was more strongly correlated with establishment success than mean suitability). Data assembled from the Global Amphibian Assessment through NatureServe provided the most accurate models for amphibians, while ecoregion data compiled by the World Wide Fund for Nature yielded models which described reptile climatic suitability better than available point-locality data. We present three methods of assigning a climate-match score for use in risk assessment using both the mean and maximum climatic suitabilities. Managers may choose to use different methods depending on the stringency of the assessment and the available data, facilitating higher resolution and accuracy for herpetofaunal risk assessment. Climate-matching has inherent limitations and other factors pertaining to ecological interactions and life-history traits must also be considered for thorough risk assessment. [ABSTRACT FROM AUTHOR]

Abstract: Invasive alien trees and shrubs pose significant threats to biodiversity and ecosystem services in South African fynbos ecosystems. An ambitious initiative, the Working for Water program, commenced in 1995 to reduce the extent and impact of plant invasions. Despite substantial progress, the problem remains immense, and innovative ways of improving the efficiency of control operations are urgently needed. This study sought to develop a robust conceptual framework for effective management of the most important invasive alien plant (IAP) species. Two methods were applied in exploring the complexity of problems, thereby identifying appropriate response strategies. The DPSIR (Driving forces-Pressure-State-Impacts-Responses) framework and the Analytic Hierarchy Process (AHP) tool were used to design a strategy for prioritizing management actions. This strategy considers explicitly the most influential factors that determine the distribution, abundance, spread and impacts of IAPs. Efficient management of IAPs is constrained by multiple interacting environmental and socio-economic factors. Factors related to the fire-prone nature of the ecosystem and the characteristics of the invasive stands emerged as pivotal features for setting spatially-explicit priorities for management. Results of the analyses provide an objective and quantifiable perspective for improving the management efficiency. We conclude that considerable progress in controlling the spread of IAPs in fynbos ecosystems could be achieved by better coordination of management practices and by improving the quality of species distribution data. [Copyright &y& Elsevier]

A correction to the article "Managing biological invasions: charting courses to desirable futures in the Cape Floristic Region" that is published in this issue is presented.