Community ecology of infectious diseases: mechanisms maintaining pathogen and host diversity Identifying the causes and consequences of biological diversity remains a major challenge in ecology. Although pathogens are highly diverse, we lack a more general understanding of how the rules of community ecology apply to them. The objective of this research is to examine what maintains pathogen diversity in nature, and how pathogen diversity affects host community dynamics. The model system being studied is the barley and cereal yellow dwarf viruses (B/CYDVs) in California grasslands. B/CYDVs are a group of viruses spread by aphids that infect hundreds cultivated and wild grasses, such as wheat and barley, causing significant damage. The consequences of pathogen diversity include decreased yields and poor grain quality. Mathematical modeling will help researchers understand the causes and consequences of pathogen diversity. The fellowship training will enhance the postdoctoral fellow's mathematical skills and lab skills such as molecular techniques for identifying viruses. B/CYDVs are important not only as a model system for studying disease in wildlife, but also as a crop pest, so results of this fellowship may inform agricultural practices. The postdoctoral fellow will involve undergraduates in research, deliver department seminars, give guest lectures in Population Ecology and Disease Ecology and participate in public outreach via programs at the UC Hopland Research and Extension Center.