MSB: Conflicts among members of interacting symbioses: How do symbiotic fungi influence plant defense against leaf-cutting ants?

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Plants and insects host a wide diversity of beneficial fungi. Previous studies have focused on the reciprocal benefits within a particular host-symbiont pair, but have rarely investigated interactions among more complex or linked symbioses. Interactions will be investigated between fungi that are part of two separate symbiont pairs; i) leaf-cutting ants and their fungal gardens, and ii) tropical plants and foliar endophytes, cryptic fungi within leaves. The former involves ants and the fungus they cultivate as a food crop. The latter is a widespread but less well understood association. In some cases foliar endophytes provide benefits by chemically defending leaves against herbivores. Laboratory and field experiments will be used to test whether the presence of endophytes reduces the harvesting efficiency and long-term development of ant colonies. The ecological implications of such costs are significant because mature leaf-cutting ants cause severe defoliations in forests, in reforestation plots, and in human agriculture. In addition to the implications for plant communities, this project will describe how leaf-cutting ants manage a wide spectrum of microbes that are potential antagonists to their fungal crops, and will elucidate costs of controlling such infections through time. Leaf-cutter ants cause an estimated US$1 billion in damages per year to agriculture and agroforestry. Understanding how nest density is limited naturally could lead to environmentally-friendly forms of biological control and lessen the economic impact of these ants. Additional broader impacts will result from increasing participation of under-represented groups by involving collaborators and students from Panama. The project includes a bi-lingual educational outreach program to Panamanian and U.S. K-12 students via video link. Allowing students from different countries to interact with researchers and with each other via video-link will simultaneously bridge the students? appreciation for biological and cultural diversity.