Effects of landscape and habitat quality on butterfly communities in pre-alpine calcareous grasslands

Habitat size and isolation are considered important drivers for the persistence of insects in fragmented landscapes. In contrast, habitat quality and the composition of the landscape matrix have only recently received more attention. To investigate the effects of habitat area, functional connectivity, landscape context and habitat quality, we analyzed species richness and density of butterfly communities in pre-alpine calcareous grasslands. Through standardized transect walks in meadows (n = 26), pastures (n = 12), and recently abandoned grasslands (n = 8), we sampled butterflies and burnet moths, as well as environmental parameters. Habitat specialist species were found in higher numbers if the habitat patches were surrounded by forests rather than non-habitat grasslands. Furthermore, the number of host plants had a positive influence on butterfly diversity and density. Habitat generalists were not affected by any of the landscape variables, but had higher species numbers and densities if the abundance of nectar plants was higher. In contrast to other studies, we showed that the impact of habitat quality on butterfly communities is more important than landscape effects. The proportion of calcareous grassland in our study region seemed to generally be too high to observe fragmentation effects. Contrary to expectations, surrounding forest increased the species richness of habitat specialists in the habitat patch.

► Integration of landscape matrix into connectivity measures (functional connectivity).
► Habitat quality more important than landscape effects in low-fragmented landscapes.
► Host plants essential for habitat specialists and nectar plants for generalists.
► Management needed to preserve high biodiversity of pre-alpine calcareous grasslands.