Sixty years of species diversity and population density decline of freshwater mussels in a global biodiversity hotspot

Abstract

The worldwide decline in freshwater biodiversity due to rising anthropogenic pressures is of growing concern. Much evidence reveals that biodiversity loss and taxonomic homogenization results in loss of ecosystem functions. Understanding temporal and spatial patterns of biodiversity is, a major challenge in ecological conservation. Of all groups of threatened aquatic animals, freshwater mussels are responsible for critical trophic and non-trophic functions. Based on published inventories and field surveys, here we aim to evaluate whether freshwater mussel diversity, density and biomass has changed in the last 60 years, as well as the factors driving these patterns in different areas within the Poyang Lake basin, a global biodiversity hotspot in the middle reach of the Yangtze River. Results showed that alpha diversity has declined in the current period (2016–2020) as compared to diversity in the historical (1960–2003) and intermediate periods (2003–2014). Overall species richness declined by 28 % over 60 years. Density and biomass also declined by 79 % and 42 %, respectively. Population declines led to homogenization of freshwater mussel faunas. Additionally, there was a significant association between pH and alpha and beta diversity, suggesting that acidification related to intensive agriculture development may be one major factor behind mussel declines. In summary, this study provides new insights into the patterns and drivers of freshwater mussel population dynamics in the Poyang Lake basin. The results have implications for the design of freshwater protected areas to slow, and even reverse, current declines.

Keywords

• Unionoida
• Biodiversity loss
• Regional homogenization
• Habitat degradation
• Asia