Evolutionary innovation can allow a species access to a new ecological niche, potentially reducing competition with closely related species. While the vast majority of Drosophila flies feed on rotting fruit and other decaying matter, and are harmless to human activity, Drosophila suzukii, which has a morphologically modified ovipositor, is capable of colonizing live fruit that is still in the process of ripening, causing massive agricultural damage. Here, we conducted the first comparative analysis of this species and its close relatives, analysing both ovipositor structure and fruit susceptibility. We found that the ovipositor of the species most closely related to D. suzukii, Drosophila subpulchrella, has a similar number of enlarged, evolutionarily derived bristles, but a notably different overall shape. Like D. suzukii, D. subpulchrella flies are capable of puncturing the skin of raspberries and cherries, but we found no evidence that they could penetrate the thicker skin of two varieties of grapes. More distantly related species, one of which has previously been mistaken for D. suzukii, have blunt ovipositors with small bristles. While they did not penetrate fruit skin in any of the assays, they readily colonized fruit interiors where the skin was broken. Our results suggest that considering evolutionary context may be beneficial to the management of invasive species.

Western Pond Turtles (Actinemys marmorata) are endemic to western North America and are found in a diversity of aquatic habitats. To date, few studies have examined the ecology of populations in ephemeral or intermittent ponds. Here, we studied the terrestrial habitat requirements of Western Pond Turtles in an intermittent pond that dries in years with below-average rainfall. We tracked terrestrial movements of Western Pond Turtles in an ephemeral pond at the San Joaquin Experimental Range in Madera County, California, USA, in the western foothills of the Sierra Nevada. We used radiotelemetry in 2012-13 to record their terrestrial locations and timing of departure from, and return to, the pond. Also, we examined the terrestrial microhabitat turtles selected for aestivation and overwintering. Turtles began leaving the pond as it dried in the late spring and early summer, spending an average of 235 d out of water, and their return to the pond was correlated with increasing rainfall during late winter. The majority of terrestrial locations were concealed completely in litter or duff and 95% of terrestrial locations during the study occurred within 187 m of the pond edge. Turtles in our study generally exhibited terrestrial habitat use similar to that of populations in intermittent lotic systems such as the many snow-melt and rain-fed rivers in northern California. Our results reinforce the importance of terrestrial habitat in the life history of Western Pond Turtles and the context-dependence of their habitat needs.

The world’s “100 worst invasive species” were listed in 2000. The list is taxonomically diverse, often cited (typically for single-species studies), and its species are frequently reported in global biodiversity data bases. We acted on the principle that these notorious species should be well-reported to help answer two questions about global biogeography of invasive species (i.e., not just their invaded ranges): (1) “how are data distributed globally?” and (2) “what predicts diversity?” We collected location data for each of the 100 species from multiple data bases; 95 had sufficient data for analyses. For question (1), we mapped global species richness and cumulative occurrences since 2000 in (0.5 degree)2 grids. For question (2) we compared alternative regression models representing non-exclusive hypotheses for geography (i.e., spatial autocorrelation), sampling effort, climate, and anthropocentric effects. Reported locations of the invasive species were spatially-biased, leaving large gaps on multiple continents. Accordingly, species richness was best explained by both anthropocentric effects not often used in biogeographic models (Government Effectiveness, Voice & Accountability, human population size) and typical natural factors (climate, geography; R2 = 0.87). Cumulative occurrence was strongly related to anthropocentric effects (R2 = 0.62). We extract five lessons for invasive species biogeography; foremost are the importance of anthropocentric measures for understanding invasive species diversity patterns and large lacunae in their known global distributions. Despite those knowledge gaps, advanced models here predict well the biogeography of the world’s worst invasive species for much of the world.