Phylogenetic diversity of ants along an elevation gradient in a dry climate: a case study in the Caatinga Domain

Elevation gradients represent useful models for testing how different organisms respond to ecological and anthropogenic gradients. We investigated how the phylogenetic diversity of ground ants change along an elevation gradient in the Brazilian semiarid, in the Caatinga Domain. We sampled the structure and composition of species from the woody community and ground ants at three elevation levels (S1: 400 m asl; S2: 500 m asl; S3: 600 m asl). We distributed five 0.01 ha plots in each elevation level, and in each plot, a transect containing six traps, totaling 15 plots, 15 transects and 90 traps. Based on genus phylogeny, we calculated the phylogenetic diversity (PD), Net Relatedness Index (NRI) and the Nearest Taxon Index (NTI). We observed that the phylogenetic diversity of ants was greater in S2 and that the taxa were more related than expected at random in S3. We also observed that the density and composition of plant species has changed along the gradient, reflecting a successional gradient. Our results demonstrate that the phylogenetic diversity of soil ant communities in the caatinga changes according to elevation, even at small amplitudes, as in the small mountains of the Brazilian semiarid region (serras). Local factors such as soil and use history can be decisive in the structuring of these communities.