Evolutionary change can occur on ecological time scales and affect species interactions, food web dynamics, and ecosystem processes. However, the importance of evolutionary change relative to ecological processes remains largely unknown. We conducted a selection experiment in which plant populations evolved for three generations in either drought or high soil moisture environments. We then used a reciprocal transplant design to compare the relative importance of contemporary drought stress and plant evolutionary responses to drought for belowground microbial communities and nutrient dynamics.
Results/Conclusions
On average, plants that evolved in drought stress supported higher bacterial and fungal richness and higher fungi:bacteria ratios. These evolutionary effects were similar in magnitude, and in some cases stronger than, the ecological effects of contemporary drought. In contrast, ecological effects were more important than evolutionary effects in explaining soil nitrogen availability. More importantly, we detected strong interactive effects between ecological and evolutionary effects, indicating that the strengths and directions 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 evolutionary perspective is required to fully understand these feedbacks. Adaptive changes in a focal population may have far-reaching consequences for other community members and ecosystem processes.