Functional and taxonomic diversity of macroinvertebrates present opposite patterns in tropical estuarine ecosystems

Abstract

The determination of the processes that act in the assembly of the communities is a theme of growing interest among ecologists. Different processes (e.g., environmental filtering and biotic interactions) can shape the structure of communities depending on the spatial scale analyzed. In this study, we partitioned the functional and taxonomic diversity of polychaete and molluscs communities of tropical estuaries from the hot and humid region, named as typical, and from the semi-arid region into the alpha, beta, and gamma components. The biological communities were sampled in three typical tropical estuaries (Paraíba do Norte, Mamanguape and Passos) and three semi-arid estuaries (Galinhos, Tubarão and Casqueira) once in each dry and rainy period. We used Rao's quadratic entropy and Simpson's index, respectively, to partition the functional and taxonomic diversity. Our results showed that when functional diversity was considered, the alpha component (diversity within sites) presented higher proportions in relation to beta diversity. For taxonomic diversity, the opposite occurred, with higher proportions of beta diversity (diversity between sites). This trend was observed in both seasonal periods. Our results indicate that different processes act in the assembly of the functional and taxonomic diversity of molluscs and polychaetes at different spatial scales. More specifically, biotic interactions seem to be more important in the assembly of functional diversity, while environmental filtering and dispersal limitation seems to have a greater effect on taxonomic diversity. Therefore, functional and taxonomic approaches provided complementary results on the distribution patterns of estuarine communities at different spatial scales.