Habitat diversity enhances ant diversity in a naturally heterogeneous Brazilian landscape

摘要

Understanding the factors that drive species richness and composition at multiple scales is of crucial importance for conservation. Here we evaluated how habitat heterogeneity—at the local and landscape scales—affects the diversity of ants in the Brazilian Cerrado. The Cerrado is a biodiversity hotspot that is characterized as a mosaic of habitats, including savannas of variable structure (the dominant vegetation), grasslands, and forests. We sampled ground-dwelling ants in four habitats, representing a gradient of increasing tree cover and decreasing grass cover. Twelve sites, distributed along two degrees of latitude, were sampled. Our sampling revealed a highly diverse and patchily distributed fauna comprising 150 species (from 44 genera), of which nearly 40% were found in only one site. On average, we found fewer species in the least structurally complex habitat. However, there was relatively little variation in species density among the remaining habitats despite strong differences in vegetation structure among them. Ant species composition varied markedly among sites and such differences were related to variations in vegetation structure but not to inter-site distances (latitude). Similar results were obtained when overall ant species richness (γ diversity) was partitioned additively into three components: α₁ (diversity within sampling sites), β₁ (diversity among sites within the same habitat type), and β₂ (diversity among sites from different habitats). The β₂ component contributed much more to γ diversity than did the remaining diversity components, indicating that conservation of the Cerrado ant fauna depends on the maintenance of habitat diversity.