Responding to soil fungal communities: a look at interactions between arbuscular mycorrhizal fungi and the common yellow monkeyflower

UC 327

The obligate fungal mutualists arbuscular mycorrhizal fungi (AMF) colonize the roots approximately 80% of vascular plants, generally thought to provide mineral nutrition, pathogen protection, or drought resistance to plants in exchange for photosynthetic carbon. Because of the ecological and evolutionary significance of these interactions, much work has been done to understand this symbiosis at the community level. However, much remains to be understood about how AMF affect plant fitness on an individual level. In this study, I took advantage of the tractability of the emerging model species Mimulus guttatus, the common yellow monkeyflower, to identify genetic differences in how contrasting annual and perennial populations respond to AMF. Specifically, I tested for differences in plant dependency on AMF, and variation in local adaptation to native AMF communities. I conducted a full factorial common garden greenhouse experiment using plant, soil, and inoculum from each contrasting field site. I found no dependency on AMF in either population and no local adaptation to native AMF communities. These results suggest that there is little genetic difference in how these contrasting annual and perennial populations interact with AMF. The presence of AMF did not confer a fitness advantage to either plant type and was often associated with a fitness cost, despite differences in life history, providing evidence for a potentially antagonistic relationship between M. guttatus and AMF under certain conditions, consistent with the theory that more ruderal species are less likely to benefit from AMF.