Ecological drivers of macroinvertebrate metacommunity assembly in a subtropical river basin in the Yangtze River Delta, China.

Identifying the underlying ecological drivers of macroinvertebrate community assembly is fundamental to metacommunity ecology. Comparably, determining the influence of different drivers on beta diversity patterns can provide insight into processes governing community organization. Exploring the ecological drivers of metacommunity and beta diversity are major avenues to improve bioassessment, restoration, and river management, which are still poorly explored in China, especially in subtropical highly developed river networks. To address this gap, we use a dataset (macroinvertebrate communities and environmental variables) collected from the Yangtze River Delta, China to test the above ideas. We used the K-means clustering method to divide 405 river sites into three anthropogenic impacted groups, nearly pristine sites, moderately impacted sites, and heavily impacted sites, and subsequently used partial Mantel tests to investigate how species sorting and dispersal shaped the metacommunity that varied with the levels of anthropogenic impacts and to explore the responses of different components of beta diversity to environmental and spatial distances among sites for each group. Our results revealed that both species sorting and dispersal shape communities, but the importance of species sorting and dispersal varied with the levels of anthropogenic impacts. Nearly pristine sites were mostly shaped only by species sorting, while heavily impacted sites were shaped by dispersal. We also found that turnover was by far the dominant component of beta diversity across all levels of impact. Therefore, we encourage that environmental variables and spatial processes should be considered in bioassessment approaches. In addition, it is essential to focus on maintaining habitat heterogeneity and identifying and protecting regional species pools that could improve local biodiversity through dispersal for ecosystem management of the Yangtze River Delta of China.