OCCURRENCE OF THE LEAF-CUTTING ANT Atta sexdens L. (HYMENOPTERA: FORMICIDAE) RELATED TO UNPAVED ROADS IN TWO BRAZILIAN SEMIARID AREAS WITH CONTRASTING DISTURBANCE DEGREES

Abstract

In the semiarid Brazilian Caatinga, we compared the occurrence of leaf-cutting ant nests (Atta sexdens) at two areas in Contendas do Sincorá, Bahia State: one single disturbed area subjected to cattle overgrazing (Fazenda Lagoa das Covas: FLC) and one protected area characterized by well-preserved patches of caatinga (Floresta Nacional Contendas do Sincorá: FNCS). We also tested if A. sexdens nests were more abundant near roads. No nest was observed in the FNCS, whereas 35 nests were recorded in the FLC (3.6 colonies ha-1). The number of A. sexdens nests clearly decreased with increasing road distance, which varied from zero to about 140 m. Nests were also observed on roads outside FLC and FNCS. We suggest that roads may be facilitating the expansion of A. sexdens range in the Caatinga vegetation at Contendas do Sincorá. We expect that A. sexdens presence will maintain or even increase the disturbing effects of cattle overgrazing on FLC vegetation. If A. sexdens also succeed to establish in FNCS, this protected area will experience a possible process of flora homogenization and impoverishment, favoring the establishment of plant species associated to anthropogenic disturbances. It is possible that other Caatinga areas are being subjected to the same process of Atta invasion favored by the establishment of paved and unpaved roads.