Respostas da comunidade de formigas à fragmentação de habitats

• Autor(a) principal: Guerra Sobrinho, Tathiana
• Data de Publicação: 2005
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/853
• topic: Fragmentação de habitats; Diversidade de espécies; Formicidae; Conservação da natureza; Habitat fragmentation; Species diversity; Formicidae; Nature conservation; CNPQ::CIENCIAS BIOLOGICAS::ECOLOGIA

Habitat fragmentation has been pointed as a main cause of changes of species richness, abundance and composition in tropical environments. This thesis aimed to test hypotheses relative to alterations of ant species richness and composition generated by forest fragmentation. The mechanisms tested were: invasion by matrix species, colonization and extinction, and edge and shape effects. Data from the first and second paper presented were collected in 17 ad 18 remnants, respectively, in the region of Viçosa, varying from 3 to 300 ha and in ten pastures around the remnants. Sampling have been carried out during three consecutive years, allowing the study of the local extinction and colonization rates, whereas sampling in the matrix occurred in only one of these three years. Baited pitfall traps were used and the number of samples in the remnants was proportional to their areas. Sampling of the third paper of this thesis were carried out in ten remnants with areas ranging from 3 to 100 ha, in which ten 1m2 samples of litter were collected in the edge of the remnants, and other ten in the center of the remnants. Litter samples were sifted and put into a Winkler extractor, to remove the ants. Remnant areas and isolation were determined using aerial photographs. Proportional sampling showed an increase of species richness with increase of remnant area. Furthermore, smaller remnants were more homogeneous in species composition than larger remnants, and potentially more invasion-prone by matrix species, because they presented proportionally more species in common with the matrix than larger remnants. Even though the degree of isolation has not influenced the colonization rate, the local extinction rates were higher in the smaller remnants, pattern that may be explained by the smaller ant population density in these remnants. Although the colonization rates did not vary with remnant area, generalist ants colonized more frequently the smaller remnants, whereas specialist ants colonized more the larger remnants. There were also differences in relation to the extinction rates within remnants, and generalist ants presented higher extinction in the forests, independently of their areas. There were higher species richness in the center than remnants edge, and there were no relationship between species richness and the distance from the forest edge. Concluding, forest fragmentation caused alterations on ant species composition and these changes are more pronounced in smaller remnants, which sustain smaller populations and are more prone to invasion and to edge and shape effects, because they present a higher relative edge.