Declining chironomid diversity in relation to human influences in southwest China

Abstract

The presence of a large altitude gradient makes southwest China an area with among the highest biodiversity in the world. While studies on biodiversity in this region have primarily focused on plant, plankton , and bacterial communities, how diversity of zoobenthos changes along the altitude gradient remains unclear. Based on surveys of water column, lake surface sediments, human population density and chironomids from 129 lakes in southwest China, we calculated the chironomid diversity to investigate the pattern of diversity in lakes varied in altitude. We also employed multiple linear regression analysis to decipher the main driver for the patterns of diversity and tease out the role of human influences. The chironomid composition showed a large divergence around 3000 m a.s.l. Contrary to the generally accepted positive relationship between biodiversity and temperature, supported by ecological theories, results showed that chironomids exhibited poorer diversity in low-altitude lakes (below 3000 m a.s.l.). The β -diversity partitioning also revealed that species gain/loss was more prevalent in these low-altitude lakes. Human population density primarily controlled the chironomid diversity in low-altitude lakes, whereas the organic matter of sediments mostly determined the diversity in lakes at high altitudes (above 3000 m a.s.l.). These results suggest that humans have replaced altitude in importance as a driver of diversity in low-altitude lakes. Considering the likelihood of increased human activities and climate change in the future, findings of this study suggest that the diversity of low-altitude lakes is subject to greater risks than those at high altitudes, not only in China but also worldwide. Greater attention to conservation measures in these types of lakes is therefore necessary.