Anthropogenic habitat alternation significantly decreases α- and β-diversity of benthopelagic metacommunity in a large floodplain lake

Anthropogenic habitat alternation is one of the leading causes of biodiversity loss, especially in freshwater ecosystems. Understanding the mechanisms of how habitat degradation drives changes in spatial patterns of species assemblages is fundamental to conservation science. We conducted an empirical study to investigate the species richness (alpha-diversity) and community composition (beta-diversity) of benthopelagic biota along the gradient of human modification in West Dongting Lake, China. The study site is a large floodplain lake that has been subjected to long-term intensive human use. For a better understanding of how beta-diversity responds to human disturbance, we also distinguished between two patterns of beta-diversity, i.e., turnover and nestedness. We found that both alpha- and beta-diversity of the benthopelagic assemblage decreased along the intensity gradient of human modification, indicating the strong homogenizing effect of anthropogenic habitat alternation. Our results also suggested that multiple processes, including environmental filtering, dispersal limitation, and biological interactions, were important in shaping the benthopelagic assemblage structure because spatial turnover other than nestedness dominated the total beta-diversity at both the lake and habitat level. These findings support that habitat restoration by removing artificial banks and channels and increasing the landscape naturalness would be the key for this highly modified floodplain lake.