Persistence of species in a fragmented urban landscape: the importance of dispersal ability and habitat availability for grassland butterflies

Some species cope with, and survive in, urban areas better than others. From a conservation viewpoint it is important to understand why some species are rare or are excluded in the urban landscape, in order that we might take action to conserve and restore species. Two ecological factors that might explain the distribution and abundance of butterfly species in the urban landscape are dispersal ability and the availability of suitable habitat. The influence of these factors was assessed by examining the distribution and genetic structure of four grassland butterfly species in the West Midlands conurbation, UK. The four species differ in their distribution and abundance, mobility and habitat specificity. No significant fit to the isolation-by-distance model was found for any of the study species at this spatial scale. Mean F-ST values revealed a non-significant level of population structuring for two species, Pieris napi (L.) and Maniola jurtina (L.), but moderate and significant population differentiation for Pyronia tithonus (L.) and Coenonympha pamphilus (L.). Results suggest that these species are limited more by the availability of suitable habitat than by their ability to move among habitat patches. Conservation strategies for these grassland species should initially focus on the creation and appropriate management of suitable habitat. More sedentary species that have already been excluded from the conurbation may require a more complex strategy for their successful restoration.