A distância ambiental e geográfica determinando a similaridade da assembleia de peixes em uma planície de inundação Neotropical.

Abstract

The similarity between communities in majority can be explained by environmental (environmental heterogeneity) and geographic (dispersive capacity) distances. Floodplains are typically heterogeneous, and it is common that similar environments in floodplains are more spatially distant than heterogeneous environments, what aids the understanding of the importance of each distance to the assembly. Thus, we hypothesized that, i) the environmental distance (lentic and semi-lotic; with/without macrophyte) determines the richness and the composition of the fish assemblages ii) the geographic distance determines the similarity of the fish assemblages. In this study, we used three rivers of upper Parana river floodplain with lentic and semi-lotic environment with and without the macrophytes presence and in different geographical distances. In order to summarize the patterns in fish assemblages composition in relation to environmental distance (factors - river: Baia, Ivinhema and Paraná; environment: lentic and semi-lotic, and macrophytes: with and without) we realized a PCoA and the difference in composition between the three factors was tested with a trifactorial PERMANOVA. The geographical distances were tested with a Pearson correlation between similarity values from a starting point, and the geographical distance (in km) of the points from where the samples were collected. Regarding the importance of the environmental heterogeneity (environmental distance), the presence of the macrophytes in the lentic environments changed significantly the fish fauna, but this did not occur in the semi-lotic environments, where the similarity between environments with and without macrophytes was higher. On the other hand, the hypothesis that the geographical distance influences the similarity was accept in environments without macrophytes. With macrophytes, the effect of distance was not significant, because these plants act like filters to pre-adapted species, independently of the dispersion distance.