Number in parentheses is the number of species in each category cRate
of population variability for each order was calculated as the number of species that had variable responses among sites divided by the number of species that occurred at more than one site, times 100. “na” signifies that none of the species occurred at multiple sites Variability was also high among populations of species: Vistusertib solubility dmso for both endemic and introduced taxa, roughly one-third to two-thirds of the species that occurred at more than one site responded to ants differently at different sites (Tables 3, 4). This population-level variability was not dependent on which species of ant was invading. Of 195 comparisons of paired population responses, pairs CYT387 chemical structure in which both populations (of the same Saracatinib arthropod species) were invaded by Argentine ants had a nearly identical ratio of same to different responses as did pairs of populations in which one was invaded by Argentine ants and the second was invaded by big-headed ants (Argentine—Argentine pairs exhibited the same response 49.1% of the time, Argentine—big-headed pairs exhibited the same response 46.8% of the time; Chi-square = 0.100, P = 0.752, Supplementary Table 6). Discussion Oceanic island faunas are well
known for their vulnerability to extinction. Island endemic species, for example, account for over 60% of documented animal extinctions worldwide (May et al. 1995). Many of these extinctions can be attributed at least in part to impacts resulting from introductions of wholly new faunal elements, such as terrestrial mammals (Simberloff 1995; Balmford 1996). Although arthropod extinctions and their causes are much more poorly documented, it has long been suggested that species endemic to remote
oceanic archipelagos possessing few or Tideglusib no native social insects are similarly ill-equipped, due to their evolutionary isolation, to withstand the novel predatory and competitive pressures of invasive ants (e.g., Zimmerman 1970; Howarth 1985; Gillespie 1999). In the present study examining the impacts of invasive ants on arthropod species in five Hawaiian communities, provenance was strongly associated with vulnerability. Both rare and non-rare endemic species were more likely than introduced species to be less abundant or absent in invaded plots, even after adjusting for such traditionally important factors as population density, trophic role and body size, and additionally controlling for ant density and major phylogenetic effects. This result is largely in accordance with the impressions and findings of biologists going back nearly a century (Krushelnycky et al. 2005).