Recovery of dung beetle assemblages in regenerating Caatinga dry forests following slash-and-burn agriculture

Abstract

Understanding patterns of tropical forest resilience is a central challenge in conservation ecology particularly in seasonally-dry tropical forests, where anthropogenic disturbance and climate change are pervasive threats. Here, we investigate the recovery rate and community organization of dung beetles along a Caatinga dry forest regeneration cline in the context of slash-and-burn agriculture in northeast Brazil. Assemblages were described considering a wide set of attributes, including abundance, taxonomic (Hill orders D0, D1 and D2) and functional diversity (functional richness, evenness and redundancy) and taxonomic/functional composition, across a chronosequence consisting of regenerating and old-growth forest stands exposed to different levels of aridity and chronic disturbance. In addition, we use body mass, diet, food relocation behaviour and habitat specificity of dung beetles as ecological attributes. Our results show that Caatinga dry forests supports dense but relatively impoverished dung beetle assemblages at both local and landscape scales, with the same small set of species dominating local assemblages. Dung beetles do not experience successional replacements along the regeneration gradient, with evidence of high resilience. Moreover, disturbance-associated dung beetle species (predominantly small-bodied generalists) resulted in assemblage convergence across the regeneration cline. Finally, chronic anthropogenic disturbance was a decisive driver of changes in abundance and taxonomic diversity, while aridity positively affected species composition and functional richness. These patterns resulted in the occurrence of spatially structured assemblages in response to a combination of both natural and anthropogenic variables, while under little or no influence of forest regeneration status across human-modified Caatinga landscapes. We conclude that the absence of directional changes in dung beetle assemblages through the forest succession pathway of regenerating second-growth forest is associated with the effect of aridity and human disturbances on community organization, including selection for certain species and functional groups, which in turn, can alter important ecological functions and consequently the resilience of dry forests.