Environmental and landscape changes drive medium- to large-bodied mammal species composition across an Amazon-Cerrado ecotone amid the deforestation expansion

Abstract Amazon and Cerrado biomes embrace a vast parcel of Brazilian biodiversity, yet remain understudied in terms of species diversity and distribution, particularly in transitional zones. We investigated the patterns of distribution and multiples facets of medium- to large-bodied mammal diversity across the ecotonal Guaporé river basin, including the relationship of biodiversity variations according to landscape-scale features, such as forest remnants and agribusiness. We sampled mammal fauna via camera-trapping and census, across six independent sites, totalling a sampling effort of 540 camera-trap-days and 720 h census. We also extracted landscape-scale covariables to further predicts the variation in mammalian diversity. Our results revealed that all sites have similar species richness, whereas the zeta-diversity decline ∼90 % when all sites were compared. Differences in species richness – even inconspicuous – and decay of shared species can be associated to the environmental gradient and distance among sites, evidencing a faunistic transictions prompted by rarity and endemism in transitional regions and human-induced landscape changes. The variations in the beta-diversity were caused by a turnover-type structure, once ∼66 % of the balanced variation in composition was due to changes in species distribution across the gradient. Considering the imminent threats to the natural habitats, it is crucial to prioritize the conservation of any natural habitat across the Guaporé basin, given that gamma diversity depends on a vast quantity of native areas. This strategy serves as a fundamental cornerstone for maximizing overall biodiversity conservation across tropical forests.