As interações tróficas de um pequeno peixe predador podem ser preditas pelas características ambientais? Um estudo de caso com Piabarchus stramineus (Characidae)

Abstract

In the literature, we find many studies that describe fish feeding and make it possible to characterize their diets. These studies gave birth to the experimental approach to evaluate interactions between consumption rates and environmental characteristics. Generalist species usually change their diets according to availability in the environment and, therefore, their diet must be influenced by local environmental characteristics, that drive diversity and availability of food resources. We evaluated if abiotic characteristics of streams belonging to the Upper Paraná River can influence the structuring of trophic interaction networks of a small insectivorous fish species. We analyzed the diet of 425 specimens in 17 stretches of streams in three sub-basins of the Upper Paraná River, the most representative resource being autochthonous insects, followed by allochthonous insects. The main source of variation in the diet was the length gradient between individuals, followed by spatial variation (sub-basins), with a greater trophic breadth niche in streams in the lower portion of the basins and with low water electrical conductivity. The trophic network of P. stramineus did not show a nested behavior. We did not find variability in the trophic position in response to the environmental gradient, however, the complexity of the trophic networks, modularity and complementary specialization were significantly explained by the altitude and electrical conductivity of the water. Therefore, our data demonstrate that environmental characteristics can influence the structuring interacting network of P. stramineus and yours preys.