The primary goal of this project is to determine if the interaction between grasses and their fungal symbionts follows predictions from mutualism theory. To accomplish this goal, the investigators will determine if an asexual fungal symbiont is a stronger mutualist than a sexual one. Both can live within Canada wild rye grass. The sexual and asexual symbionts will be assessed for the amount of herbivore resistance they provide to their host through alkaloid production. The project will employ molecular genetic and analytical chemistry approaches to assess the regulation and expression of the fungal genes responsible for alkaloid production. To complement these physiological approaches, the investigators will determine the degree of genetic diversity in populations of Canada wild rye and its asexual and sexual symbionts across a broad geographic range, from Texas to Minnesota. Furthermore, field and mesocosm experiments will be performed to determine how endophytes affect plant fitness within an ecosystem level context. The project will contribute to the fields of symbiosis and community ecology as well as result in the training of 26 undergraduate students, approximately 30% of whom will be from groups typically underrepresented in science, technology, engineering and mathematics. Students will work as part of a multidisciplinary team, learning to develop hypotheses, design and conduct experiments, analyze data, and report their findings. Collaboration between the labs at Hope College and Indiana University-Kokomo will be fostered through joint annual meetings. The impact of the proposed research will be extended by publishing the scientific findings in ecological peer-reviewed journals and by presentations at national scientific meetings. Moreover, basic scientific knowledge gathered through this research will contribute to the understanding and management of fungal endophytes in forage grasses, where they can cause considerable economic loss due to harmful effects of alkaloids on livestock.