Microbial biogeography of acid mine drainage sediments at a regional scale across southern China.

Investigations of microbial biogeography in extreme environments provide unique opportunities to disentangle the roles of environment and space in microbial community assembly. Here, we reported a comprehensive microbial biogeographic survey of 90 acid mine drainage (AMD) sediment samples from 18 mining sites of various mineral types across southern China. We found that environmental selection was strong in determining the AMD habitat species pool. However, microbial alpha diversity was primarily explained by mining sites rather than environmental factors, and microbial beta diversity correlated more strongly with geographic than environmental distance at both large and small spatial scales. Particularly, the presence/absence of widespread AMD habitat generalists was only correlated with geographic distance and independent of environmental variation. These distance-decay patterns suggested that spatial processes played a more important role in determining microbial compositional variation across space; which could be explained by the reinforced impacts of dispersal limitation in less fluid, spatially structured sediment habitat with diverse pre-existing communities. In summary, our findings suggested that the deterministic assembling and spatial constraints interact to shape microbial biogeography in AMD sediments; and provided implications that spatial processes should be considered when predicting microbial dynamics in response to severe environmental change across large spatial scales.