Spatial structure of aquatic communities and dispersal pathway selection: an empirical study based on near-natural...

The spatial structure of aquatic communities is shaped by both environmental filtering and dispersal limitation. In watershed ecosystems, species may disperse through overland and watercourse pathways, and their dispersal abilities can influence their reliance on these pathways. In this study, we examined environmental factors, algae, macroinvertebrates, and zooplankton in a near-natural mountainous watershed. Distance-decay relationships (DDR) and linear regressions (LR) were used to evaluate communities' similarity with geographic distance and to assess dispersal limitation. Variation partitioning analysis (VPA) quantified the relative contributions of overland and watercourse pathways and examined how macroinvertebrate dispersal ability affects dependence on these pathways. The results indicate that all three aquatic communities experienced significant dispersal limitation, which explained more variation in community structure than environmental filtering. Watercourse pathways accounted for communities' structure more effectively than overland pathways, while macroinvertebrates with higher dispersal abilities showed lower reliance on watercourse pathways. These findings provide a scientific basis for watershed ecological management and underscore the importance of considering multiple dispersal pathways in studies of community assembly.