Fungus systematics and ecology with emphasis on mushrooms and related fungi. Our studies range from taxonomic and phylogenetic studies of genera to species diversity and richness in forest, alpine and arctic ecosytems. We examine species distributions over broad geographical ranges and across plant communities, and evaluate the temporal and spatial patterns of species in a variety of habitats. A main focus has been ectomycorrhizal fungi, especially agarics, for example, the large mushroom genus Cortinarius, in conifer forests of the Pacific Northwest. We work to better define species concepts in these fungi and to solve patterns of distribution and speciation in relation to vegetation, host specificity and edaphic factors, such as soil pH.