Exploring ecological and evolutionary causes of the plant-fungal symbiosis (Visiting Scholar)
The vast majority of seed plants form symbioses with soil fungi, which provide plants with nutrient uptake services in return for sugars from photosynthesis. Even though it is widespread, the symbiosis can vary in its taxonomic specificity and the magnitude and direction of plant growth response to inoculation. Some of this variability can be explained by natural selection for parasitism because net benefits of the interaction would increase for a partner that exploits the other. However, the persistence of the symbiosis as a mutualism suggests that natural selection may not favor cheating in specific life history and ecological contexts. For example, long-lived plant species may sanction fungal partners who cheat, or selection for cheating may not occur when resources are severely limited or the climate is stressful. I propose to test whether the symbiosis is influenced by life history and ecological context by combining and then analyzing existing databases that contain information on the identity of the fungal and plant partners, plant growth response to inoculation, plant functional and life history traits, and plant climatic requirements. This work will provide a foundation for future empirical tests of these mechanisms as causes of the evolution of the symbiosis.