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We present a generic scoring system that compares the impact of alien species among members of large taxonomic groups. This scoring can be used to identify the most harmful alien species so that conservation measures to ameliorate their negative effects can be prioritized. For all alien mammals in Europe, we assessed impact reports as completely as possible. Impact was classified as either environmental or economic. We subdivided each of these categories into five subcategories (environmental: impact through competition, predation, hybridization, transmission of disease, and herbivory; economic: impact on agriculture, livestock, forestry, human health, and infrastructure). We assigned all impact reports to one of these 10 categories. All categories had impact scores that ranged from zero (minimal) to five (maximal possible impact at a location). We summed all impact scores for a species to calculate \"potential impact\" scores. We obtained \"actual impact\" scores by multiplying potential impact scores by the percentage of area occupied by the respective species in Europe. Finally, we correlated species' ecological traits with the derived impact scores. Alien mammals from the orders Rodentia, Artiodactyla, and Carnivora caused the highest impact. In particular, the brown rat ( Rattus norvegicus), muskrat ( Ondathra zibethicus), and sika deer ( Cervus nippon) had the highest overall scores. Species with a high potential environmental impact also had a strong potential economic impact. Potential impact also correlated with the distribution of a species in Europe. Ecological flexibility (measured as number of different habitats a species occupies) was strongly related to impact. The scoring system was robust to uncertainty in knowledge of impact and could be adjusted with weight scores to account for specific value systems of particular stakeholder groups (e.g., agronomists or environmentalists). Finally, the scoring system is easily applicable and adaptable to other taxonomic groups.

We provide a cross-taxon and historical analysis of what makes tropical forest species vulnerable to extinction. Several traits have been important for species survival in the recent and distant geological past, including seed dormancy and vegetative growth in plants, small body size in mammals, and vagility in insects. For major past catastrophes, such as the five mass extinction events, large range size and vagility or dispersal were key to species survival. Traits that make some species more vulnerable to extinction are consistent across time scales. Terrestrial organisms, particularly animals, are more extinction prone than marine organisms. Plants that persist through dramatic changes often reproduce vegetatively and possess mechanisms of die back. Synergistic interactions between current anthropogenic threats, such as logging, fire, hunting, pests and diseases, and climate change are frequent. Rising temperatures threaten all organisms, perhaps particularly tropical organisms adapted to small temperature ranges and isolated by distance from suitable future climates. Mutualist species and trophic specialists may also be more threatened because of such range-shift gaps. Phylogenetically specialized groups may be collectively more prone to extinction than generalists. Characterization of tropical forest species' vulnerability to anthropogenic change is constrained by complex interactions among threats and by both taxonomic and ecological impediments, including gross undersampling of biotas and poor understanding of the spatial patterns of taxa at all scales. /// Aportamos un análisis trans-taxón e histórico de lo que hace que las especies de bosques tropicales sean vulnerables a la extinción. Varios atributos han sido importantes para la supervivencia de especies en el pasado reciente y geológico, incluyendo la latencia de semillas y el crecimiento vegetativo en plantas, el tamaño corporal pequeño de mamíferos y la vagilidad en insectos. Para las mayores catástrofes del pasado, como los cinco eventos de extinción masiva, la extensión del rangoy la vagilidad o dispersión fueron claves para la supervivencia de especies. Los atributos que hacen que algunas especies sean más vulnerables a la extinción son consistentes a través de las escalas de tiempo. Los organismos terrestres, particularmente animales, son más propensos a la extinción que los organismos marinos. Las plantas que persisten a través de cambios dramáticos a menudo se reproducen vegetativamente y poseen mecanismos de muerte regresiva. Las interacciones sinérgicas entre amenazas antropogénicas actuales, como explotación de madera, fuego, cacería, plagas y enfermedades y cambio climático son frecuentes. Las temperaturas crecientes amenazan a todos los organismos, quizás particularmente a organismos tropicales adaptados a rangos de temperatura pequeños y aislados por distancia de climas futuros adecuados. Las especies mutualistas y los especialistas tróficos pueden estar más amenazados debidos a taies discontinuidades en los cambios de rango. Losgrupos filogenéticamente especializados colectivamente pueden ser más propensos a la extinción que los generalistas. La caracterización de la vulnerabilidad de las especies de bosques tropicales al cambio antropogénico está limitada por las complejas interacciones entre amenazas y tantopor impedimentos taxonómicos y ecológicos, incluyendo el muestreo incompletos de biotas y elpobre entendimiento de los patrones espaciales de taxa a todas las escalas.

To explain current plant invasions, or predict future ones, more knowledge on which factors increase the probability of alien species becoming naturalized and subsequently invasive is needed. We created a database of the alien plants in seminatural habitats in Ireland that included data on taxonomy, invasive status, invasion history, distribution, and biological and ecological plant characteristics. We used information from this database to determine the importance of these factors in increasing the ability of species to become naturalized and invasive. More specifically, we used two multiple logistic regressions to identify factors that distinguish naturalized from casual alien plant species and invasive from noninvasive, naturalized alien species. Clonal growth, moisture-indicator value, nitrogen-indicator value, native range, and date of first record affected (in order of decreasing importance) the probability of naturalization. Factors that distinguished invasive from noninvasive species were ornamental introduction, hermaphrodite flowers, pollination mode, being invasive elsewhere, onset of flowering season, moisture-indicator value, native range, and date of first record. Incorporation of phylogenetic information had little influence on the results, suggesting that the capacity of alien species to naturalize and become invasive evolved largely independently in several phylogenetic lineages. Whereas some of the variables were important for both transitions, others were only important for naturalization or for invasion. This emphasizes the importance of studying different stages of the invasion process when looking for mechanisms of becoming a successful invasive plant, instead of simply comparing invasive with noninvasive alien species. Our results also suggest that a combination of species traits and other variables is likely to produce the most accurate prediction of invasions.

Public preferences are likely to play an important role in prioritizing species at risk for conservation. We conducted a survey of British Columbians (Canada) (n =555, r =73%) to examine how the public ranks a species' attributes (rather than named species) with respect to conservation priority. Endemism, defined as species only or mainly occurring in British Columbia or species occurring in British Columbia and nowhere else in Canada, was considered the most important among the measured attributes. This preference was strongest among men and among respondents who had completed postsecondary education. The preference for endemism is generally consistent with science-based federal listings of British Columbian species. This congruence between listing and public opinion is welcome if such congruence is considered important. We suggest that investigating how much the public values species' attributes, as opposed to named species, provides a more efficient way of incorporating public opinion into policies on species at risk, especially if large numbers of species must be ranked for conservation priority.