Landscape-scale patterns and drivers of novel mammal communities in a human-modified protected area

Context The role of protected areas as biodiversity repositories has become increasingly important in face of increased deforestation. By adding free-living exotic mammals, removing forest-dependent native ones, isolating forest patches from large protected areas and reducing landscape forest cover, human activities may drive mammal communities towards regional biotic homogenization. Objectives We assessed how landscape forest cover and proximity to the largest and best-preserved area of the Catimbau National Park-one of the largest protected areas of the Brazilian Caatinga-affect alpha- and beta-diversity of medium- and large-sized mammals, considering native and exotic species. Methods Using camera traps (total effort of 2340 cameras/day), we obtained 823 records of 15 species (8 natives and 7 exotics) in 18 landscapes of 1-km radius. We estimated diversity metrics within and among landscapes and used generalized linear models to assess the effect of forest loss and isolation on diversity metrics. Results As expected, forest loss decreased alpha-diversity of native species and increased the diversity and relative abundance of exotics. However, proximity to the preserved area showed weak effect on alpha-diversity, suggesting that this area does not work regionally as source for natives neither as ecological trap for exotics. Supporting the biotic homogenization hypothesis, beta-diversity of natives decreased and beta-diversity of exotics increased in more deforested landscapes. Yet, species composition was weakly related to forest cover and isolation. Conclusions Our findings demonstrate that deforestation jeopardizes native species, favors exotics, and drives mammal communities towards biotic homogenization. Protected areas should be properly implemented to safeguard mammal diversity.