Padrões de forrageamento e biomassa vegetal consumida por Atta laevigata (Hymenoptera : Formicidae) em uma área do cerrado brasileiro

Abstract

Leaf-cutting ants of the genus Atta (Formicidae: Attini) are considered highly generalist herbivores, and they have been frequently referred to as the most prevalent herbivores in the Neotropics. However, most studies on leaf-cutter ants were conducted in lowland tropical rain forests. There is only limited knowledge of the foraging patterns of these ants in Brazilian Cerrado. In this study I determined the diversity of attacked plants by Atta laevigata, patterns of plant selection, and the amount of plant biomass consumed. A. laevigata colonies had a generalist behavioral, attacking 102 plant species. This represented 73 89% of the available plant species. There was a clear distinction between the species composition of attacked plants by colonies and the species composition of the plant community surrounding the nests. I estimate that leaf-cutter ants harvest 17.7% of the leaves produced by cerrado trees, shrubs and vines. This is approximately 2-3 fold more damage than is caused by all other insect herbivores combined. Furthermore, these estimates of herbivory by leaf-cutters are higher than those calculated for tropical rain forests (range = 1.6-17%). Given their selectivity, the frequent defoliation of attacked plants, and the heterogeneous exploration of the area surrounding their nests, leaf-cutting ants probably have a strong influence on the Cerrado vegetation. This could be especially true for highly fragmented and disturbed sites, where Atta populations are greatly elevated.