Symbioses between plants and mycorrhizal fungi are wide-spread, ecologically important phenomena that are poorly understood. These mutualistic relationships can affect the partners in a variety of ways particularly influencing herbivory on the plant hosts. In grassland ecosystems where these relationships are ubiquitous, their influence on herbivory may operate by affecting plant tolerance of herbivory rather than simply providing defense against it. This project will integrate considerations of herbivory, plant tolerace and mycorrhizal symbiosis in evaluating ineractions between herbivores, fungi and host plants. It tests the general hypotheses that the cost/benefit balance of plant/fungal symbioses are altered by the amount of herbivory in a habitat and that mycorrhizal fungi influence the tolerance and defenses of host plants of herbivores. It will test these hypotheses in a series of tallgrass prairie mesocosm and field experiments that are being conducted at the Konza Prairie Research Natural Area to examine the general influence of three different potentially limiting resources, light, N and P. This work wil further the understanding of the roles and interactions of hervivores, fungal mutualists, and host plants which accomplish important biotic interactions in grassland ecosystems. It will increase the understanding of plant-fungal mutualism, particularly by evaluating the constraints of a third party, a herbivore, on the stability of the symbioses.
