Risks posed by invasive species to the provision of ecosystem services in Europe.

Invasive species significantly impact biodiversity and ecosystem services, yet understanding these effects at large spatial scales remains a challenge. Our study addresses this gap by assessing the current and potential future risks posed by 94 invasive species to seven key ecosystem services in Europe. We demonstrate widespread potential impacts, particularly on outdoor recreation, habitat maintenance, crop provisioning, and soil and nitrogen retention. Exposure to invasive species was higher in areas with lower provision of ecosystem services, particularly for regulating and cultural services. Exposure was also high in areas where ecosystem contributions to crop provision and nitrogen retention were at their highest. Notably, regions vital for ecosystem services currently have low invasion suitability, but face an average 77% increase in potential invasion area. Here we show that, while high-value ecosystem service areas at the highest risk represent a small fraction of Europe (0-13%), they are disproportionally important for service conservation. Our study underscores the importance of monitoring and protecting these hotspots to align management strategies with international biodiversity targets, considering both invasion vulnerability and ecosystem service sustainability.

Using the IUCN Environmental Impact Classification for Alien Taxa to inform decision-making.

The Environmental Impact Classification for Alien Taxa (EICAT) is an important tool for biological invasion policy and management and has been adopted as an International Union for Conservation of Nature (IUCN) standard to measure the severity of environmental impacts caused by organisms living outside their native ranges. EICAT has already been incorporated into some national and local decision-making procedures, making it a particularly relevant resource for addressing the impact of non-native species. Recently, some of the underlying conceptual principles of EICAT, particularly those related to the use of the precautionary approach, have been challenged. Although still relatively new, guidelines for the application and interpretation of EICAT will be periodically revisited by the IUCN community, based on scientific evidence, to improve the process. Some of the criticisms recently raised are based on subjectively selected assumptions that cannot be generalized and may harm global efforts to manage biological invasions. EICAT adopts a precautionary principle by considering a species' impact history elsewhere because some taxa have traits that can make them inherently more harmful. Furthermore, non-native species are often important drivers of biodiversity loss even in the presence of other pressures. Ignoring the precautionary principle when tackling the impacts of non-native species has led to devastating consequences for human well-being, biodiversity, and ecosystems, as well as poor management outcomes, and thus to significant economic costs. EICAT is a relevant tool because it supports prioritization and management of non-native species and meeting and monitoring progress toward the Kunming-Montreal Global Biodiversity Framework (GBF) Target 6.

Uso de la Clasificación de Impacto Ambiental de los Taxones Exóticos de la UICN para la toma de decisiones Resumen La Clasificación de Impacto Ambiental de los Taxones Exóticos (EICAT, en inglés) es una herramienta importante para las políticas y manejo de las invasiones biológicas y ha sido adoptada como un estándar de la Unión Internacional para la Conservación de la Naturaleza (UICN) para medir la seriedad del impacto ambiental causado por los organismos que viven fuera de su extensión nativa. La EICAT ya ha sido incorporada a algunos procedimientos locales y nacionales de toma de decisiones, lo que la vuelve un recurso particularmente relevante para abordar el impacto de las especies no nativas. Algunos principios conceptuales subyacentes de la EICAT han sido cuestionados recientemente, en particular aquellos relacionados con el uso del principio de precaución. Aunque todavía son relativamente nuevas, las directrices para la aplicación e interpretación de la EICAT tendrán una revisión periódica, basada en evidencia científica, por parte de la comunidad de la UICN para mejorar el proceso. Algunas de las críticas recientes están basadas en suposiciones seleccionadas subjetivamente que no pueden generalizarse y podrían perjudicar los esfuerzos globales para manejar las invasiones biológicas. La EICAT adopta un principio de precaución cuando considera el historial de impacto de una especie en cualquier otro lugar ya que algunos taxones tienen características que podrían volverlos más dañinos. Además, las especies no nativas suelen ser factores de pérdida de bidiversidad, incluso bajo otras presiones. Cuando ignoramos el principio de precaución al abordar el impacto de las especies no nativas, hay consecuencias devastadoras para el bienestar humano, la biodiversidad y los ecosistemas, así como resultados pobres de conservación, y por lo tanto con costos económicos importantes. La EICAT es una herramienta relevante porque respalda la priorización y el manejo de las especies no nativas y ayuda con el cumplimiento y monitoreo del progreso para llegar al objetivo 6 del Marco Mundial de Biodiversidad Kunming-Montreal.

The EICAT+ framework enables classification of positive impacts of alien taxa on native biodiversity.

Species introduced through human-related activities beyond their native range, termed alien species, have various impacts worldwide. The IUCN Environmental Impact Classification for Alien Taxa (EICAT) is a global standard to assess negative impacts of alien species on native biodiversity. Alien species can also positively affect biodiversity (for instance, through food and habitat provisioning or dispersal facilitation) but there is currently no standardized and evidence-based system to classify positive impacts. We fill this gap by proposing EICAT+, which uses 5 semiquantitative scenarios to categorize the magnitude of positive impacts, and describes underlying mechanisms. EICAT+ can be applied to all alien taxa at different spatial and organizational scales. The application of EICAT+ expands our understanding of the consequences of biological invasions and can inform conservation decisions.

Consensus and controversy in the discipline of invasion science.

Approaches, values, and perceptions in invasion science are highly dynamic, and like in other disciplines, views among different people can diverge. This has led to debate in the field specifically surrounding the core themes of values, management, impacts, and terminology. Considering these debates, we surveyed 698 scientists and practitioners globally to assess levels of polarization (opposing views) on core and contentious topics. The survey was distributed online (via Google Forms) and promoted through listservs and social media. Although there were generally high levels of consensus among respondents, there was some polarization (scores of ≥0.39 [top quartile]). Relating to values, there was high polarization regarding claims of invasive species denialism, whether invasive species contribute to biodiversity, and how biodiversity reporting should be conducted. With regard to management, there were polarized views on banning the commercial use of beneficial invasive species, the extent to which stakeholders' perceptions should influence management, whether invasive species use alone is an appropriate control strategy, and whether eradication of invasive plants is possible. For impacts, there was high polarization concerning whether invasive species drive or are a side effect of degradation and whether invasive species benefits are understated. For terminology, polarized views related to defining invasive species based only on spread, whether species can be labeled as invasive in their native ranges, and whether language used is too xenophobic. Factor and regression analysis revealed that views were particularly divergent between people working on different invasive taxa (plants and mammals) and in different disciplines (between biologists and social scientists), between academics and practitioners, and between world regions (between Africa and the Global North). Unlike in other studies, age and gender had a limited influence on response patterns. Better integration globally and between disciplines, taxa, and sectors (e.g., academic vs. practitioners) could help build broader understanding and consensus.

Los enfoques, valores y percepciones en el campo de las invasiones biológicas son muy dinámicos, y como en otras disciplinas científicas, los expertos pueden tener distintas opiniones. Esto ha creado debates, especialmente sobre temas relacionados con valores, gestión, impactos y terminología. Considerando estos debates, encuestamos a 698 científicos y gestores de todo el mundo para evaluar sus niveles de polarización (opiniones opuestas) sobre una serie de temas fundamentales y polémicos. La encuesta fue distribuida a través de internet (a través de Google Forms) y promovida por medio de listas de correo electrónico y redes sociales. Aunque, en general, hubo consenso entre los encuestados, hubo cierta polarización (puntuaciones de ≥ 0.39 [cuartil más alto]). En relación con valores, hubo una gran polarización sobre aquellas declaraciones relacionadas con el negacionismo de especies invasoras, si las especies invasoras contribuyen a aumentar la biodiversidad y cómo se deberían llevar a cabo los informes sobre biodiversidad. En relación con la gestión, hubo opiniones polarizadas sobre la prohibición del uso comercial de especies invasoras beneficiosas, si la opinión de las partes interesadas debería influir en la gestión, si el uso de especies invasoras por sí solo es una estrategia de control adecuada y si la erradicación de plantas invasoras es factible. En cuanto a impactos, hubo gran polarización en cuanto a sí las especies invasoras conducen a o son un efecto lateral de la degradación de ecosistemas y ssi los beneficios de las especies invasoras están subestimados. En cuanto a terminología, encontramos opiniones polarizadas relacionadas con definir especies invasoras exclusivamente en base a su expansión, si las especies se pueden considerar invasoras en sus rangos de distribución nativos y si el lenguaje utilizado en el campo de las invasiones biológicas es xenofóbico. Los análisis factoriales y de regresión revelaron que las opiniones de los expertos encuestados fueron particularmente divergentes entre personas que trabajan con diferentes taxones (plantas y mamíferos) en diferentes disciplinas (entre biólogos y sociólogos), entre científicos y gestores y entre regiones del mundo (entre países de África y del hemisferio Norte). A diferencia de otros estudios, la edad y el género tuvieron una influencia limitada sobre lass respuestas obtenidas. Una mejor integración global y entre disciplinas, taxones y sectores (o. e., investigadores vs. gestores) podría contribuir a alcanzar un mayor entendimiento y consenso.

Land cover, individual's age and spatial sorting shape landscape resistance in the invasive frog Xenopus laevis.

The description of functional connectivity is based on the quantification of landscape resistance, which represents species-specific movement costs across landscape features. Connectivity models use these costs to identify movement corridors at both individual and population levels and provide management recommendations for populations of conservation interest. Typically, resistance costs assigned to specific land cover types are assumed to be valid for all individuals of the population. Little attention has been paid to intraspecific variation in resistance costs due to age or dispersal syndrome, which may significantly affect model predictions. We quantified resistance costs in an expanding invasive population of the African clawed frog Xenopus laevis in Western France. In this principally aquatic amphibian, juveniles, sub-adults and adults disperse overland. The enhancement of dispersal traits via spatial sorting has been also observed at the range periphery of the population. Resistance costs, and thus connectivity, might vary as a function of life stage and position within the invaded range. We assessed multiple dimensions of functional connectivity. On various land cover types, we measured locomotion, as crossing speed, in different post-metamorphic age classes, and dehydration, sensitivity of locomotion to dehydration and substrate preference in juveniles. We also tested the effect of the position in the invaded range (core vs. periphery) on individual performances. In juveniles, general trends towards higher resistance costs on grass and lower resistance costs on bare soil and asphalt were observed, although not all experiments provided the same cost configurations. Resistance to locomotion varied between age classes, with adults and sub-adults facing lower costs than juveniles, particularly when crossing structurally complex land cover types such as grass and leaf litter. The position in the range had a minor effect on landscape resistance, and only in the dehydration experiment, where water loss in juveniles was lower at the range periphery. Depicting functional connectivity requires (a) assessing multiple dimensions of behavioural and physiological challenges faced by animals during movement; (b) considering factors, such as age and dispersal syndrome, that may affect movement at both individual and population levels. Ignoring this complexity might generate unreliable connectivity models and provide unsupported management recommendations for conservation.

La description de la connectivité fonctionnelle est basée sur la quantification de la résistance du paysage, lequel représente pour une espèce les coûts de déplacement au travers des éléments du paysage. Les modèles de connectivité utilisent ces coûts pour identifier les corridors de déplacement à l'échelle des individus et des populations et fournir des recommandations de gestion pour les populations présentant un intérêt pour la conservation. En général, les coûts de résistance attribués à chaque type de couverture du sol sont supposés valides pour tous les individus de la population. Peu d'attention a été accordée à la variation intraspécifique des coûts de résistance, due à l'âge ou au syndrome de dispersion, qui pourrait affecter de manière significative les prévisions du modèle. Nous avons quantifié les coûts de résistance dans une population invasive en expansion de Xénope lisse Xenopus laevis dans l'ouest de la France. Chez cet amphibien principalement aquatique, les juvéniles, les sous-adultes et les adultes se dispersent par voie terrestre. Le renforcement des traits liés à la dispersion par le tri spatial a également été observée en périphérie de l'aire de répartition de la population. Les coûts de résistance, et donc la connectivité, pourraient varier en fonction du stade de vie des individus et de leur position dans l'aire colonisée. Nous avons évalué plusieurs dimensions de la connectivité fonctionnelle. Sur divers types de substrat du sol, nous avons mesuré la locomotion (vitesse de déplacement) à tous les stades post-métamorphiques, la déshydratation, la sensibilité de la locomotion à la déshydratation et la préférence de substrat chez les juvéniles. Nous avons également testé l'effet de la position dans l'aire colonisée (centre vs. périphérie) sur les performances individuelles. Chez les juvéniles, des tendances générales vers des coûts de résistance plus élevés sur l'herbe et des coûts de résistance plus faibles sur sol nu et asphalte ont été observées, bien que toutes les expériences n'aient pas produit les mêmes configurations de coûts. La résistance à la locomotion a varié selon les classes d'âge, les adultes et les subadultes subissant des coûts moindres que ceux des juvéniles, en particulier lors de la traversée de substrats structurellement complexes comme l'herbe et la litière de feuilles. La position dans l'aire de répartition a eu un effet mineur sur la résistance du paysage, et seulement dans l'expérience de déshydratation, où la perte d'eau chez les juvéniles était plus faible à la périphérie de l'aire. Pour décrire la connectivité fonctionnelle, il faut: i) évaluer les multiples dimensions des défis comportementaux et physiologiques auxquels les animaux sont confrontés pendant leurs déplacements; ii) en tenant compte des facteurs, tels que l'âge et le syndrome de dispersion, qui peuvent influer sur les déplacements tant au niveau individuel qu'au niveau de la population. Ignorer cette complexité pourrait générer des modèles de connectivité peu fiables et fournir des recommandations de gestion non étayées pour la conservation.

A global meta-analysis of the ecological impacts of alien species on native amphibians.

The exponential increase in species introductions during the Anthropocene has brought about a major loss of biodiversity. Amphibians have suffered large declines, with more than 16% considered to be threatened by invasive species. We conducted a global meta-analysis of the impacts of alien species on native amphibians to determine which aspects of amphibian ecology are most affected by plant, invertebrate, fish, amphibian, reptile, or mammal introductions. Measures of fitness were most strongly affected; amphibian performance was consistently lower in the presence of alien species. While exposure to alien species caused a significant decrease in amphibian behavioural activity when compared with a no species control, this response was stronger towards a control of native impacting species. This indicates a high degree of prey naiveté towards alien species and highlights the importance of using different types of controls in empirical studies. Alien invertebrates had the greatest overall impact on amphibians. This study sets a new agenda for research on biological invasions, highlighting the lack of studies investigating the impacts of alien species on amphibian terrestrial life-history stages. It also emphasizes the strong ecological impacts that alien species have on amphibian fitness and suggests that future introductions or global spread of alien invertebrates could strongly exacerbate current amphibian declines.

Rapid adaptive response to a Mediterranean environment reduces phenotypic mismatch in a recent amphibian invader.

Invasive species frequently cope with ecological conditions that are different from those to which they adapted, presenting an opportunity to investigate how phenotypes change across short time scales. In 2000, the guttural toad Sclerophrys gutturalis was first detected in a peri-urban area of Cape Town, where it is now invasive. The ability of the species to invade Cape Town is surprising as the area is characterized by a Mediterranean climate significantly drier and colder than that of the native source area. We measured field hydration state of guttural toads from the invasive Cape Town population and a native source population from Durban. We also obtained from laboratory trials: rates of evaporative water loss and water uptake, sensitivity of locomotor endurance to hydration state, critical thermal minimum (CTmin) and sensitivity of CTmin to hydration state. Field hydration state of invasive toads was significantly lower than that of native toads. Although the two populations had similar rates of water loss and uptake, invasive toads were more efficient in minimizing water loss through postural adjustments. In locomotor trials, invasive individuals noticeably outperformed native individuals when dehydrated but not when fully hydrated. CTmin was lower in invasive individuals than in native individuals, independent of hydration state. Our results indicate that an invasive population that is only 20 years old shows adaptive responses that reduce phenotypic mismatch with the novel environment. The invasion potential of the species in Cape Town is higher than we could infer from its characteristics in the native source population.

How repeatable is the Environmental Impact Classification of Alien Taxa (EICAT)? Comparing independent global impact assessments of amphibians.

The magnitude of impacts some alien species cause to native environments makes them targets for regulation and management. However, which species to target is not always clear, and comparisons of a wide variety of impacts are necessary. Impact scoring systems can aid management prioritization of alien species. For such tools to be objective, they need to be robust to assessor bias. Here, we assess the newly proposed Environmental Impact Classification for Alien Taxa (EICAT) used for amphibians and test how outcomes differ between assessors. Two independent assessments were made by Kraus (Annual Review of Ecology Evolution and Systematics, 46, 2015, 75-97) and Kumschick et al. (Neobiota, 33, 2017, 53-66), including independent literature searches for impact records. Most of the differences between these two classifications can be attributed to different literature search strategies used with only one-third of the combined number of references shared between both studies. For the commonly assessed species, the classification of maximum impacts for most species is similar between assessors, but there are differences in the more detailed assessments. We clarify one specific issue resulting from different interpretations of EICAT, namely the practical interpretation and assigning of disease impacts in the absence of direct evidence of transmission from alien to native species. The differences between assessments outlined here cannot be attributed to features of the scheme. Reporting bias should be avoided by assessing all alien species rather than only the seemingly high-impacting ones, which also improves the utility of the data for management and prioritization for future research. Furthermore, assessments of the same taxon by various assessors and a structured review process for assessments, as proposed by Hawkins et al. (Diversity and Distributions, 21, 2015, 1360), can ensure that biases can be avoided and all important literature is included.

Frog eat frog: exploring variables influencing anurophagy.

Background. Frogs are generalist predators of a wide range of typically small prey items. But descriptions of dietary items regularly include other anurans, such that frogs are considered to be among the most important of anuran predators. However, the only existing hypothesis for the inclusion of anurans in the diet of post-metamorphic frogs postulates that it happens more often in bigger frogs. Moreover, this hypothesis has yet to be tested. Methods. We reviewed the literature on frog diet in order to test the size hypothesis and determine whether there are other putative explanations for anurans in the diet of post-metamorphic frogs. In addition to size, we recorded the habitat, the number of other sympatric anuran species, and whether or not the population was invasive. We controlled for taxonomic bias by including the superfamily in our analysis. Results. Around one fifth of the 355 records included anurans as dietary items of populations studied, suggesting that frogs eating anurans is not unusual. Our data showed a clear taxonomic bias with ranids and pipids having a higher proportion of anuran prey than other superfamilies. Accounting for this taxonomic bias, we found that size in addition to being invasive, local anuran diversity, and habitat produced a model that best fitted our data. Large invasive frogs that live in forests with high anuran diversity are most likely to have a higher proportion of anurans in their diet. Conclusions. We confirm the validity of the size hypothesis for anurophagy, but show that there are additional significant variables. The circumstances under which frogs eat frogs are likely to be complex, but our data may help to alert conservationists to the possible dangers of invading frogs entering areas with threatened anuran species.