Many losers and few winners in dung beetle responses to Amazonian forest fragmentation

Abstract

Tropical forest fragmentation is expected to result in the loss of forest-dependent species (‘losers’) and proliferation of disturbance-tolerant species (‘winners’). Here, we use multi-species occupancy modelling to quantify the effects of fragmentation on Amazonian dung beetles at the species and community level. We investigate the relationship between species' habitat preferences and fragmentation responses to understand how interspecific variation in fragmentation responses translates into patterns of alpha and beta diversity. We sampled dung beetles within 21 forest patches and 2 continuous forests. For each site, we quantified three fragmentation metrics (area, shape, and surrounding forest amount) and modelled their effects on species occurrence and community properties. Most species were most likely to occur within large forest patches, while surrounding forest amount had a positive impact on all species. Over 80 % of species were forest specialists and species' area responses were positively correlated with their level of forest specialization. Observed species-level responses were reflected at the community level, with greater representation of forest specialists in larger forest patches up to an 88-ha threshold, stabilizing thereafter; this threshold was met by only 1 % of patches in the landscape. Species richness also increased with patch area, although surrounding forest amount had a greater positive impact. Communities were structured by a gradient of species turnover from small to large patches, and among more isolated patches. Our findings show that most Amazonian dung beetle species become ‘losers’ within fragmented landscapes, particularly forest specialists. We recommend landscape-scale planning to retain forest connectivity including large forest remnants.