Clay 97 27116 Biotic interactions have long been of considerable interest in ecology particularly in light of their interactions with diversity in influencing ecosystem processes. One of the more widespread and potentially important of such interactions is the symbiosis occurring between grasses and fungi that live within their cells. In this project, the PI, Keith Clay, will take advantage of an association between endophytic fungi and tall fescue, Festuca arundinacea, a species that occurs commonly in grasslands. This particular association is unusual in Festuca arundinacea occurs in strains that do or do not have fungal endophytes. This research will manipulate these two forms in experimental tests of the potential benefits of the symbionts for this grass species. Investigations will evaluate how fungal endophyte infections influence the diversity and production of Festuca arundinacea grasslands. They will also evaluate the degree to which resistance to herbivory and stress influence the dominance of endophyte-infected grasses. A series of plots will be planted with seeds of endophyte- and non-endophyte infected grass strains to examine their effects on plant diversity and production. Fencing and insecticide applications will be used to vary the levels of herbivory and the relative proportions of infected and noninfected grass strains that survive will be quantified. Ecologically marginal sites will also be planted with the two strains as well as four other fescue species to examine their overall success rates. The ultimate goal of this work will be to examine general role of microbial symbiosis in the structure and function of plant communities. This work will provide important practical information because tall fescue is one of the dominant species across the eastern US in grasslands.
