Butterflies on the dry edge of the Atlantic Forest: water availability determines community structure at the Northern limit of Atlantic Forest

Abstract

The composition of communities of fruit‐feeding butterflies in the Brazilian Atlantic forest changes in response to landscape fragmentation and can be used as an indicator of habitat quality. Landscape fragmentation, aridity, and early signs of global warming at the northernmost distribution of this biome may impose extra challenges for species persistence. We aim to clarify the drivers of fruit‐feeding butterflies' metacommunity structure in the northernmost portion of the Brazilian Atlantic Forest. We propose to disentangle consequences of habitat loss from fragmentation per se by using both habitat amount and patch scale metrics. We sampled fruit‐feeding butterflies in 15 forest fragments of up to ~30 ha during 1 year. We used fragment size, shape, distance to nearest perennial stream, Euclidean distance to nearest neighbour, forest habitat amount, proximity index, and the percentage of sugarcane within a buffer to elucidate patterns of species richness, abundance, and beta diversity. A configuration metric, stream distance, was the only variable predicting metacommunity total abundance and richness: fragments farther from water had fewer species and individuals. However, forest habitat amount and sugar cane were important to rarefied richness and species replacement between fragments. Our findings suggest that streams and associated riparian zones provide source populations for the butterfly metacommunities in this landscape, which fits the mass effect model. We also emphasise that small forest patches have high conservation value for persistence of butterfly populations, because each fragment preserves a substantial portion of the total species pool.