Composition and richness of arboreal ants in fragments of Brazilian Caatinga: Effects of secondary succession

Abstract

Ecological succession is a complex process involving mainly some changes in the structure of plant community, with subsequent changes in resource availability as well as in the interactions among organisms which are also important factors determining the structure of arboreal ant assemblages, but little is known about the consequences of secondary succession on ant assemblages in Tropical Dry Forests (TDFs), such as the Brazilian Caatinga. Here we investigate the effects of ecological succession on the richness and species composition of arboreal ants in fragments of Caatinga, testing the following hypothesis: i) the species richness of arboreal ants increases along a gradient of secondary succession, in response to habitat complexity and season; ii) species composition of arboreal ants differs among stages of secondary succession due to differences in vegetation structure in theses stages and seasonality. This study was conducted in 15 plots distributed in three areas with different stages of secondary succession (early, intermediate and late). Tree species richness and density were used as surrogates of habitat complexity. Ants were sampled using the technique of beating the foliage and baited pitfall traps, where five trees were sampled per plot, totaling 75 individual trees sampled. We sampled 37 species of ants, distributed in 16 genera and five subfamilies. Ant species richness differed among stages of succession and seasons, with higher number of species in the late succession and rainy period, also increasing with habitat complexity. We conclude that the structure of arboreal ants assemblage was related to ecological succession of vegetation, mainly in the rainy season. Fifteen years of secondary regeneration are enough to increase species richness and maybe to restore species composition of arboreal ants but secondary habitats are also important to biodiversity maintenance of this group in Caatinga.