Formigas cortadeiras (Hymenoptera, Formicidae) como agentes modificadores da disponibilidade de luz e da estrutura da comunidade vegetal em Floresta AtlÃntica Nordestina

AUTOR(ES)
DATA DE PUBLICAÇÃO

2006

RESUMO

Leaf-cutting ants of the genus Atta are important generalist herbivores of the Neotropics, with many species showing a marked preference for early successional plants. Previous studies have revealed that their enormous nest constructions (up to 200 m2) locally affect the abundance and species richness of the plant community. Moreover, leaf harvesting activities have been demonstrated to increase light intensity substantially above the nests and moderately in the surrounding foraging area. Here, we evaluated whether the increased light availability at nest sites and foraging areas can reduce the proportion of shade tolerant species in a forest remnant. We hypothesized that these species present lower frequency near ant nests and in the foraging areas because of their low light requirement to develop and grow. Our study was conduced in a 3,500-ha fragment of Atlantic forest in Serra Grande usine property (Alagoas, Brazil). To test for nest effects we selected 16 Atta cephalotes nests in the fragment. For each nest we established four plots: (1) above the nest, (2) at the border of the nest, (3) 5 m from the second plot, and (4) 20 m from the third plot. For the effects of foraging area we used the same 16 ant nests, and established for each nest, one plot inside the foraging area (treatment) and another in an ant-free area (control). In both experiments, we measured the light availability and identified all trees from 1.5 to 5.0 cm DBH, and grouped species as shade tolerant or intolerant. In both nest and foraging areas the light intensity was higher and the abundance and richeness of plants were lower than control areas. For foraging areas, proportion of shade tolerant individuals and species were higher than in control areas without ant foraging. These results suggest a clear interference of leaf-cutting ants in the species composition and structure of plant communities. Such interference is probably due to differences in light penetration to the forest floor as a consequence of Atta nest constructions and leaf harvesting activities. Considering that shade tolerant species are important components of late successional stages, the increased presence of leaf-cutting ants in fragmented environments, delay the regeneration process and increase fragmentation effects

ASSUNTO(S)

formigas cortadeiras leaf-cutting ants botanica shade tolerant species atividade de forrageamento foraging activity clareiras gaps espÃcies tolerantes à sombra floresta atlÃntica atlantic forest

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