Investigating eco-evolutionary processes of microbial community assembly in the wild using a model leaf litter system.

Microbial communities are not the easiest to manipulate experimentally in natural ecosystems. However, leaf litter - topmost layer of surface soil - is uniquely suitable to investigate the complexities of community assembly. Here, we reflect on over a decade of collaborative work to address this topic using leaf litter as a model system in southern California ecosystems. By leveraging a number of methodological advantages of the system, we have worked to demonstrate how four processes - selection, dispersal, drift, and diversification - contribute to bacterial and fungal community assembly and ultimately, impact community functioning. Although many dimensions remain to be investigated, our initial results demonstrate that both ecological and evolutionary processes occur simultaneously to influence microbial community assembly. We propose that the development of additional and experimentally tractable microbial systems will be enormously valuable to test the role of eco-evolutionary processes in natural settings and their implications in the face of rapid global change.