Homogeneização de fauna e urbanização em regiões tropicais: assembleias de anuros de duas pequenas cidades amazônicas

Abstract

Urbanization is an important cause of biotic homogenization in cities around the world. The relationship between faunal homogenization and urbanization, however, has not yet been properly investigated in Amazonian cities. In this study, we analyzed the effects of urbanization on anuran assemblages in the municipalities of Tabatinga and Itacoatiara, in the Brazilian Amazon, using the taxonomic, phylogenetic and functional dimensions of biotic homogenization. The anuran species richness was similar between the urban environments of the two municipalities, but lower than the rural environments of each city. However, when alpha diversity is measured thorugh the Fisher index, the local anuran species diversity in Itacoatiara was greater than that of Tabatinga. This result suggests that a process of homogenization in alpha diversity is not occurring. The composition of anuran species in urban habitats was quite different between the two municipalities, suggesting that taxonomic homogenization is also not affecting anuran assemblages. The taxonomic distinction (a proxy for phylogenetic diversity) was similar between the urban habitats of the two cities, indicating that the loss of species in each city did not compromise the evolutionary structure of urban anuran assemblages. Some functional traits were filtered by urbanization in a similar way in the two municipalities studied. Furthermore, functional dispersion was similar in the urban anuran assemblages of both cities, suggesting a process of functional homogenization. In contrast, the taxonomic and phylogenetic dimensions of biotic homogenization indicate a certain degree of resilience of anuran assemblages in both cities and demonstrate the complexity in the responses of biodiversity to the urbanization process. The anuran assemblages in the studied urban habitats, although impoverished in number of species, are still representative of the biogeographic regions where these cities are located. This indicates that biodiversity conservation in degraded urban environments may still be relevant. Studies that use the fauna an integrative homogenization approach should be encouraged in other urban contexts in the Amazon and may have important implications for the conservation of regional biodiversity.