Uma abordagem funcional das savanas amazônicas: atributos de anuros em um mosaico de paisagens naturais

Abstract

The structure of natural assemblages may result from selection of species and functional traits, according to their tolerance to certain environmental factors, which are related, for example, to vegetation type and water availability, may influencing functional diversity in ecosystems. We investigated the influence of different phytophysiognomies of Amazonian savannas on functional diversity of anurans, in the Carajás National Forest, Brazil. We also investigated a possible divergence of functional traits among the phytophysiognomies due to environmental differences using a null model. Three field expeditions were conducted in 2008 and 2010, during rainy season, dry season and the transition period between rainy and dry seasons. We sampled 32 sample units distributed in three sites: North highland, South highland and Tarzan highland. Each sample unit was distant at least 200 m from each other. Surveys for the presence of anurans were based in active visual and acoustic searches. We calculated functional diversity using the MPD index, considering the occurrence of anurans in each assemblage. Functional diversity of anurans did not differ among the vegetation types. According to null model, there was a functional convergence, that is, the sites are similar in species and functional traits. Our results suggest that despite the mosaic distribution and environmental differences, the landscapes are surrounded by Amazonian savanna matrix, which, due to some factors (historic, spatial, and environmental), did not differ in the functions performed by anurans in each phytophysiognomy. In any case, we found that anurans play important roles in local ecosystem functions.