Local and landscape scale effects of fragmentation on aerial insectivorous bats in the Amazon

Deforestation is the main driver of the biodiversity crisis. Resulting landscapes are left fragmented with isolated remnant forest patches embedded in a human-modified matrix which has the propensity to regenerate into successional forest. The Biological Dynamics of Forest Fragments Project (BDFFP) in the Brazilian Amazon is the world's largest fragmentation experiment which, for over 40 years, has been investigating the effects of deforestation, fragmentation and recovery on tropical biota. Amazonian aerial insectivorous bats provide vital forest ecosystem services, yet as a group they are understudied compared to their phyllostomid counterparts. This study aims to address this research gap by investigating assemblage- (via multidimensional diversity), guild- and species-level responses of aerial insectivorous bats to fragment size and interior-edge-matrix disturbance gradients and conduct a multiscale analysis of the relative influence of local versus landscape characteristics. All three facets of assemblage-level diversity exhibited degradation in the secondary forest matrix around the smallest fragments compared to continuous forest. This negative effect became less pronounced as fragment size increased and in contrast, forest edges generally contained higher diversity. We only found subtle associations for assemblage functional diversity at landscape scale. Habitat occupancy patterns were species-specific, as were responses to fragment sizes and disturbance gradients. In particular, Furipterus horrens exhibited reduced activity across the whole interior-edge-matrix gradient of the smallest fragments. We found little evidence that the local or landscape variables were negatively influencing the aerial bats at guild- or species-level. Based on our findings we suggest the aerial insectivorous bat assemblage at the BDFFP could be approaching a point of recovery after 30 years of regeneration. The advanced secondary forest is buffering the pervasive effects of fragmentation and we therefore highlight the conservation value that second-growth forests can deliver within human modified landscapes and emphasise the need for them to be protected alongside primary forest areas