Linking Functional Traits to Anthropogenic Stress: A Dung Beetle Case Study in a Degraded Habitat

Anthropogenic disturbances, such as extensive topsoil removal, pose severe threats to ecosystem integrity, and consequently restoration outcomes depend heavily on biotic interactions that sustain ecosystem functions. Dung beetles (Coleoptera: Scarabaeinae) act as bioindicators and ecosystem engineers, notably by mediating secondary seed dispersal and promoting soil bioturbation. We investigated taxonomic and functional attributes of dung beetle communities and quantified seed-removal rates in a severely degraded site (topsoil removal for dam construction) and in an adjacent, less-disturbed reference area within the Brazilian Cerrado. Contrary to our initial predictions, in the degraded site hosted higher species richness (27 vs. 26 species), greater abundance (5371 vs. 1142), and higher functional richness (FRic), whereas functional divergence (FDiv) was greater in the reference area. Community-weighted means (CWMs) for traits associated with excavation and rolling (pronotum volume, front-leg area, and hind-to-front leg length ratio) were significantly elevated in the degraded area, despite a lower mean body mass. Seed-removal rates were also significantly higher in the degraded site. Across the dataset, seed removal correlated positively with FRic, abundance, pronotum volume, front-leg area, and hind/front leg ratio, and negatively with FDiv and body mass; however, these relationships were context-dependent and largely vanished when habitats were analysed separately. Our results indicate that the dung beetle assemblage colonizing the degraded site is dominated by abundant, morphologically specialized species that can sustain high rates of seed removal despite low functional divergence. We discuss implications for restoration: the presence of functionally competent, abundant dung beetles can facilitate secondary seed dispersal in heavily degraded landscapes, but reliance on a few trait-dominant species may render this service vulnerable to further perturbation.