Environmental and spatial drivers of oligochaeta metacommunities structure along the Paraguay‐Paraná fluvial system

The metacommunity theory is a framework that explains the interdependence of local factors and regional processes as community drivers. In rivers, it has been hypothesized that the metacommunity structure and the relative importance of dispersal and local environmental conditions may vary from headwaters toward lowlands. The aims of this study were (1) to analyze the benthic metacommunity structure along the longitudinal dimension of the Paraguay‐Paraná system, and (2) to assess the relative importance of dispersal (spatial structure) and niche‐based processes as drivers of these structures. We used data of oligochaetes assemblages in the studied system and analyzed the Elements of Metacommunity Structure in different river sections. Moreover, we performed a variance partitioning analysis to determine the relative importance of spatial and environmental variables. In the upper section, we found a gradient structure (Gleasonian) and in the lower section we found random and quasi‐Clementsian structures. Similarly, environmental variables were the main structuring factor in the upper section while spatial variables were more important in the delta. The present study provides evidence that metacommunity structure and the underlying mechanisms that shape it, change along the longitudinal dimension of a large South American River. However, we emphasize the necessity of further studies assessing other taxonomic groups and other large South American Rivers.