Biotic and abiotic drivers of plant symbionts determine plant performance, the maintenance of diversity, and response to global change

Interactions among organisms regulate the structure and function of ecosystems and the response of ecosystems to global change. The outcome of species interactions is shaped by the partners involved in the interaction and the climate contexts of the systems in which they reside. Global change is altering the distributions of organisms as well as the climate contexts of the systems they reside within, shifting the biotic and abiotic factors shaping species interactions. Thus, predicting the response of ecosystem structure and function to global change remains unresolved. For my dissertation, I explored how the interactions among plants and their mutualistic communities alter individual plant, community, and ecosystem function and how these interactions are shaped by changing biotic and abiotic factors. To do this, I combined a series of experiments and observations across scales, from detailed root-­microbe experiments in laboratory mesocosms to coupled observations and experiments conducted along elevation gradients. Overall, my work provides mechanistic insights on how microbial community composition shapes the morphology and physiology of plant hosts, how plant community composition shapes the structure and function of microbial communities, and how abiotic and biotic contexts shape fungal endophyte assemblages at global scales.