Species richness and beta-diversity of aquatic macrophytes in the Upper Parana River floodplain

In this paper, we estimated the aquatic macrophyte species richness in the Upper Parana River floodplain using non-parametric estimators. Fifty specie s were recorded in intensive surveys of several floodplain habitats. Based on a random sample of 20 lagoons, 6 connected to the Parana River, 6 to one tributary and 8 to another, all estimators gave values very similar to the "true" number of species recorded in intensive surveys. The comparison amo ng the lagoons connected with these rivers showed that the species richness was different, after controlling for sampling effort. Correspondence analy sis and Mantel's test showed that the beta diversity was significantly high er among the groups of lagoons than within groups of lagoons connected with the same river. The high connectivity among the lagoons of the same river can account for such results. Within the groups of lagoons, the highest spe cies turnover (beta diversity) was found for Parana River lagoons, which ar e predominantly temporary and more variable. This result is in accordance w ith a general ecological prediction, which stresses that beta diversity sho uld increase with environmental variability.