Biodiversidade dos peixes de riachos de uma savana tropical com ênfase na ecologia trófica e atributos ecomorfológicos

Abstract

Assembly processes indicate that community structuring can be induced by both deterministic and stochastic processes, as they are not mutually exclusive. In this study I evaluated the structure of fish assemblages and their biodiversity (taxonomic and functional dimensions) in tropical savanna streams, with the intention of identifying the relationship between biodiversity and functioning of these ecosystems. Overall, this study revealed that the ichthyofauna in streams of the Cuiabá River basin, an important tributary of the Upper Paraguay River, was structured by environmental conditions, while hydrographic distance was not a limiting factor in dispersal. The most important environmental conditions were the local habitat variables, especially water turbidity, which favored (positively) both species richness and functional redundancy of the ichthyofauna. However, land use in the catchment were factors that determined the environmental conditions in the streams and thus were considered factors that indirectly structured the assemblages. Furthermore, native Cerrado vegetation had a positive effect on species richness, while agriculture had a negative effect. On the other hand, trophic ecology indicated that the assemblages are dominated by species that feed primarily on aquatic insects, although they had some degree of specialization in consumption. Furthermore, morphological traits are a good predictor of trophic guilds. In the functional dimension, functional structure patterns based on two niche axes (habitat use and trophic) revealed that the ichthyofauna is composed of more functionally similar species than expected by chance, confirming the effect of environmental filtering on structuring. However, stochastic processes were also important. It can be concluded that the assembly of species assemblages was structured by both deterministic (environmental filtering) and stochastic mechanisms. Finally, the positive relationship between functional diversity and taxonomic and functional richness leads to the conclusion that fish biodiversity is positively related to the functionality of these ecosystems. The information generated provided a broader view of the effects of environmental conditions on fish biodiversity and functionality in small streams in a Brazilian tropical savanna during the end of a dry season.