Effects of habitat fragmentation on ant richness and functional composition in Brazilian Atlantic forest

Ants are a dominant faunal group in tropical forests, but their responses to human disturbances remain poorly investigated. Here we examine the relative effects of habitat fragmentation (fragment size and amount of forest cover retained in the surrounding landscape) and habitat structure (tree density and richness) on ant species and functional composition in the Atlantic forest of northeast Brazil. Our study was carried out in 19 fragments ranging in size from 10 to 3,500 ha. We recorded 146 ant species from 41 genera. Fragment size and tree density were the most important variables predicting species richness and functional diversity. Additionally, fragment area and tree density also explained the richness of a range of global functional groups (Cryptic Species, Specialists Predators and Tropical-climate Specialists) and Atlantic forest functional groups (Cryptic Predators, Cryptic Omnivores, Epigaeic Predators and Epigaeic Omnivores). Taxonomic composition was influenced by fragment area and tree richness, while functional composition responded to forest cover and tree density. Overall variation of global functional groups was also affected by tree richness. Our results suggest that specialist ants (especially cryptic species, specialist predators and climate specialists) are particularly sensitive to forest fragmentation. Such functional groups would make useful indicators of ant responses to forest fragmentation.