Influences of dispersal and local environmental factors on stream macroinvertebrate communities in Qinjiang River, Guangxi, China

Identifying the underlying mechanisms that explain the spatial variation of stream macroinvertebrate assemblages is crucial for the protection of species diversity. Consequently, questions regarding how much variance in macroinvertebrate community structure is related to spatial dispersal and local environmental factors, and which environmental variables are the key drivers have broad research and management implications. Based on data from 22 stream sites within the Qinjiang River watershed, Guangxi, China, we examined the variation in macro invertebrate community structure attributable to local environmental factors (i.e. stream physical habitat and water chemistry) vs. spatial dispersal factors (i.e. overland and watercourse spatial eigenvectors among sampling sites) using variation partitioning procedures. Overall, we found that stream macro invertebrates are influenced both by local environmental factors and spatial dispersal factors. The most important environmental factors structuring macro invertebrate assemblages were current velocity, dissolved oxygen, conductivity, total phosphorus, and physical habitat quality. Both overland and watercourse dispersal pathways had a similar influence on macroinvertebrate assemblages. These results demonstrate that stream macroinvertebrates within the studied landscape are constrained by local environmental conditions and dispersal factors, and hence comply with the niche-based species sorting hypo thesis in the context of metacommunity ecology.