Diversidade taxonômica e funcional de aves na Mata Atlântica fragmentada : padrões e seus mecanismos

Abstract

The harmful effects caused by the fragmentation have been studied in several different taxa and habitats, the reduction of the area being the most immediate effect. However, other aspects of diversity that not only the taxonomic such as functional diversity, lack of understanding of how aspects of the fragmented landscape can affect them. The objective of this work was to evaluate the emergent patterns of the taxonomic and functional diversity of birds, as measured by species richness (S) and Pielou equability (J '), as well as functional richness (FRic), functional uniformity (FEve) , functional divergence (FDiv) and functional dispersion (FDis), along three landscape gradients (area, isolation and shape) in Atlantic Forest fragments in the Brazilian Northeast. As expected, the area was shown to positively influence S and FRic and negatively J' and FDis. Although both were positive, the S-area relationship showed a significantly higher slope value than the FRic-area, indicating the emergence of redundant bird species functionally along the gradient. This same redundancy is responsible for FEve not having a significant relationship with the area. It was identified that the influence of the isolation and the form on the diversity of birds is a reflection of the area of the fragments, because there is a spatial correlation between the landscape metrics. It was also identified that limiting similarity appears to have greater influence as the assembly rule in most of the fragments studied and that strength gains with area reduction, so that emerging patterns of diversity metrics were produced by the force of competition between species along the area gradient. As deforestation increased, bird species were subjected to stronger competitive interactions until those of lower fitness were excluded, resulting in higher FDis and J ', as well as smaller S and FRic in the smaller fragments. These results demonstrate that habitat reduction affects not only species richness but also functional diversity, reducing resilience of assemblies to stochastic events as well as the range of ecological functions exercised by birds.