Diversidade taxonômica e funcional das assembleias de peixes de riachos ao longo do gradiente urbanização-agricultura

Abstract

Headwater systems integrate various physical, chemical and biological processes in the landscape, and thus are directly influenced by the basin's land use. Environmental degradation resulting from urbanization in lower order streams is expected to reduce the taxonomic diversity and functional diversity of the fish assemblage. Nine headwaters streams stretches belonging to three watersheds of the Upper Paraná River (Londrina-PR, Brazil) were analyzed by limnological variables (electrical conductivity, turbidity, pH and dissolved oxygen), structure of riparian vegetation (forest density, mean forest diameters - 1st and 2nd planes, diametric amplitude at 6 and 15 meters, and litter cover of the soil), land use (dense vegetation, agriculture / field, exposed soil, impervious area and water mirror) and fish assemblage by taxonomic (richness and Simpson index of diversity) and functional index (richness, evenness, divergence, dissimilarity and Rao quadratic entropy). The stretches were classified as urban, intermediate and agricultural. Limnological variables varied according to urbanization gradient, except for turbidity. Taxonomic indexes were significantly higher in the agricultural sections, due to the dense vegetation cover in the sub-basin, with substitution of species and functional composition among the three classes. No significant difference was observed between the classes regarding the functional diversity indices, except for the functional richness, which was smaller in the intermediate class. The taxonomic and functional variables analyzed were negatively associated with the litter cover, since it contributed significantly to group functionally similar species.