Studies of insect herbivore impacts on plants in nature and agriculture have primarily focused on the direct interactions that occur between an herbivore and a plant. However, we know that soil organisms such as beneficial mycorrhizal fungi (which promote nutrient absorption by plants) can alter plant growth and the outcome of plant-plant interactions. Therefore, we expect that these soil organisms can also change the outcome of a plant-herbivore interaction. The research tests two novel hypotheses for predicting the outcomes of interactions between herbivores, plants and mycorrhizal fungi. The Nutrition Hypothesis suggests that increased nutrition from a plant's association with mycorrhizal fungi will directly translate into increased herbivore growth, and the Modification of Defense Hypothesis suggests that mycorrhizal fungi alter the production of plant defenses such that herbivores feeding on mycorrhizal plants experience a decrease in growth compared to herbivores feeding on non-mycorrhizal plants. Two experiments will be conducted to examine herbivory on plants associated with mycorrhizal fungi. These experiments will examine three plant defense responses; measure herbivore responses to the presence of mycorrhizae; and measure mycorrhizal responses to herbivory, thereby determining which hypothesis is most consistent with the responses exhibited by this system. Knowledge of mycorrhizal-plant-herbivore interactions will provide a predictive tool for understanding the impact of herbivores in agriculture as a function of mycorrhizal fungi in the soil community. Through work on these experiments, the PI will continue mentoring minority and female undergraduates. These students will assist with the implementation of these experiments while developing and conducting their own projects; they will improve their analytical skills, and broadened their academic preparation to enter a variety of scientific fields.
