Plant evolution in response to drought alters the structure and function of soil microbial communities
Recent evidence suggests that evolutionary changes on ecological time scales may be common, especially in response to drastic shifts in environment associated with global change. Evolution can affect species interactions, food web dynamics, and ecosystem processes, but the importance of evolution relative to ecological processes remains unknown in most systems. We conducted a selection experiment and allowed plant populations to evolve for three generations in response to drought or non-drought conditions. Following selection, we used a reciprocal transplant design to compare the relative importance of contemporary drought stress and plant evolutionary responses to drought for soil microbial community composition and the dynamics of soil nutrients.
Generally, plants that evolved in drought stress caused soils to have higher bacterial and fungal richness and higher fungi:bacteria ratios. The effect of plant evolution was similar in magnitude, and in some cases stronger than, the ecological effect of contemporary drought. In contrast, ecological effects were generally more important than evolutionary effects in explaining soil nitrogen availability. More importantly, the most important effects were interactions between ecological and evolutionary factors. The strength and direction of evolutionary effects were largely dependent on the ecological context in which they were measured. Plant-soil feedbacks are crucial for driving global nutrient cycles and plant community dynamics, but our results suggest an eco-evolutionary perspective is required to fully understand these feedbacks. Evolutionary changes in populations may have far-reaching consequences for the rest of the community, as well as ecosystem processes.