Determinantes da estrutura da assembleia de anuros em ambientes de areia branca na Amazônia.

Abstract

White sand ecosystems are one of several vegetation types present in the Amazon basin. These ecosystems are patchy distribution way and are characterized by sandy soils, with 85% or more sand, in which a distinct plant structure—ranging from open fields (campinas) dominated by herbaceous plants to tall forests (campinaranas)—is present. White sand ecosystems harbor a high level of species endemism and several species adapted to long periods of drought. We assessed the composition of anuran species in white sand environments to better understand how unique these environments are for this group of vertebrates. For this, we evaluated whether the structures of vegetation and soil, including root depth, influence the distribution and structure of anuran assemblages. At a local scale, we tested the hypothesis that anuran assemblages vary with environmental vegetation types because species are not uniformly distributed in heterogeneous environments. We carried out four field samplings in the rainy seasons, from December to March 2020 and 2021, in 20 plots, using the RAPELD/PPBio sampling model in the RDS Rio Negro, Amazonas State, Brazil. Our results show that the small proportion of clay in the soil plays an important role in structuring vegetation, and that these are the main factors that organize anuran assemblages into hierarchical subgroups. The forested environments (campinaranas) located close to water bodies harbored a higher richness of anuran species, while meadow landscapes with low vegetation, exposed soil, and more distant from water bodies limited the occupation of most anuran species. Our findings indicate that anuran species undergo environmental filtering in white sand environments, in which only species with specialized reproduction can successfully occupy the most water-restricted environments. Thus, environmental filtering is the main process responsible for organizing the assemblage of anurans in white sand environments into hierarchical subgroups.