A simplificação funcional em reservatórios neotropicais revelada através de um novo índice de invasão

Abstract

Studying the number of non-native species of fish, we aim to verify if the introduction of non native species in hydroelectric reservoirs provides functional alteration of the assembly. Fish were collected from twenty hydroelectric reservoirs, belonging to the Neotropical region. The fish were collected with waiting nets, packed in drums and sent to the laboratory. Then, the fish were identified, weighed and measured. For statistical analysis, metrics of abundance in number and biomass and species richness were selected to obtain the degree of introduction. Still, the functional traits of the species were obtained, later converted into functional indices and related to the degree of introduction through Pearson's correlation. The gradient of species introduction present between the reservoirs was significantly associated with functional indices: functional richness increases as this gradient increases, functional equitability, Rao's quadratic entropy and functional dispersion tend to decrease and functional divergence does not vary greatly depending on the introduction of species. These were the standards for most reservoirs, but we also found some caveats, like Capivari’s reservoir. It was possible to verify that non-native species lead to the functional modification of the assembly in which they are found. The importance of using different metrics is also highlighted, since the individual analysis of only one, could lead to a misinterpretation of the results.