Traits that allow bats of tropical lowland origin to conquer mountains: Bat assemblages along elevational gradients in the South American Atlantic Forest

Abstract

AbstractAimThis study aims to contribute to the identification of ecological determinants of tropical moist forest montane biodiversity, analysing changes in the structure of bat assemblages along an elevational gradient and testing the role of species traits shaping those assemblages.LocationMountain ranges in the Brazilian Atlantic Forest.MethodsWe compiled a dataset with the composition of phyllostomid bat assemblages at 32 forested sites, ranging from 60 m to 1,960 m a.s.l. We quantified how abundance and diversity changed along this elevational gradient, and assessed the capacity of each species to be present and abundant at each elevation, identifying traits that may influence that capacity.ResultsAbundance and species diversity declined markedly with increasing elevation. Tolerance to low temperatures, low habitat specialization and cave roosting facilitated success at higher elevations. Owing to trait filtering, and to changes in resource availability with elevation, assemblages were progressively dominated by a smaller number of mostly generalist species as elevation increased. Higher elevations harbour only a subset of the species that are present in the lowland forest, with no mountain specialized species.Main conclusionsHigh mountains harbour phyllostomid assemblages that are impoverished subsets of those at lower elevations. Phyllostomids have a tropical origin and may thus have a low potential to adapt to montane forest environments, which possibly explains the observed climatic trait filtering. Habitat filtering is also important, keeping forest specialists mostly at lowest elevations. Protected areas in the Atlantic Forest are mostly limited to mountains. While these areas are clearly important to protect biodiversity, including phyllostomid assemblages, it is now critical to protect and restore the few remnants of lower elevation Atlantic Forest where higher productivity and resource levels, increased complexity of vertical structure, and fewer climatic constraints favour the success of a wider range of phyllostomid bat species of tropical origin.