Dissertation Research: Partner Variability and Fitness in a Legume-Rhizobium Mutualism

Biological mutualisms are interactions between species in which both species benefit. These interactions are ubiquitous in nature. One of the best studied and economically important of these mutualisms occurs between legume plants and rhizobial bacteria, a mutualism in which plants provide food and shelter to the bacteria and the bacteria provide nitrogen to the plant. Little is known, however, about the evolutionary forces that maintain cooperation between these partners. This project will investigate coevolution between the model plant Medicago truncatula and its symbiotic bacterium Sinorhizobium meliloti. Manipulative greenhouse experiments will be used to study the effects of symbiosis on the reproductive success of both partners. These data will allow us to determine if mutualisms are optimally beneficial for both parties or fluctuate between being beneficial and parasitic.

This research will advance our knowledge of how mutualisms evolve in nature as well as contribute to an understanding of basic evolutionary processes. This knowledge will increase our ability to manage mutualistic interactions, as they often play important roles in both crop production and ecosystem restoration. Moreover, insight into these relationships will improve our understanding of the effects natural and anthropogenic changes in environmental conditions have on mutualism stability.