Threat status in butterflies and its ecological correlates: how far can we generalize?
It would be very useful for conservation biologists to be able to predict threat status from ecological characteristics of species, and past studies have shown promising results. Regarding one important threat indicator taxon, the butterflies, results from a study on Finnish species by Kotiaho et al. (Proc Natl Acad Sci USA 102:1963–1967, 2005), suggested that threatened butterflies on average have narrower niches, more restricted distributions of the larval host plants, poorer dispersal abilities and shorter flight periods. However, this study did not control for phylogenetic relatedness of species. To examine the effects of phylogenetic control, and to see how far it is possible to generalize from specific investigations, we compared the ecological characteristics of threatened and non-threatened butterfly species at two different geographical scales: Sweden and Europe. Our results illustrate the difficulties of generalizing between sites, geographical scales, scoring methods, and phylogenetic versus non-phylogenetic analyses. Controlling for phylogeny is shown to be essential. The most robust result is that threatened species have narrower habitat ranges at the local scale.