Environmental and spatial factors driving beta diversity in freshwater communities: a systematic review

Abstract The structuring of aquatic communities depends on a set of factors, such as abiotic variables, biotic interactions, and spatial processes related to species dispersal. However, the influence of these predictors varies across different spatial scales, organism groups, and ecosystems. Environmental and spatial processes are key drivers of beta diversity, and therefore this review aimed to synthesize the literature on the relative importance of environmental and spatial factors driving the beta diversity of metacommunities in freshwater ecosystems worldwide. This work focused on studies based on dissimilarity matrices, employing the techniques of distance-based redundancy analysis and variation partitioning. Forty-five articles were selected and analyzed, and the data were categorized according to organism groups, ecosystem types, spatial extents, diversity facets, and beta diversity components. The results showed that, across the entire dataset, environmental factors explained a median of 8% of the dissimilarity, while spatial factors explained 4%. Both factors contributed to the variation, but environmental factors were more important across all organism groups, ecosystem types, and beta diversity facets. The components of species replacement/turnover and total beta diversity were also predominantly explained by environmental factors, whereas the richness difference and nestedness were more strongly associated with spatial factors. The influence of environmental and spatial factors varied across different spatial scales. These findings reinforce the importance of considering multiple ecological categories and scales when studying metacommunities. Additionally, they highlight the need to incorporate other factors, such as temporal dynamics and biotic interactions, in metacommunity studies.