Ectomycorrhizal fungi play critical ecological roles in forests worldwide by forming beneficial symbiotic relationships with many kinds of trees. These symbiotic fungi absorb and transfer nutrients and water to the tree; as well, they reduce the incidence of root pathogens. In doing so they influence forest composition and succession, and certain of these fungi are routinely used in reforestation projects. However, many basic questions remain unanswered regarding the biology of the fungi that form ectomycorrhizae. Species of Laccaria and Hydnangium have been widely used as model taxa in research on this symbiotic relationship. Species in this group often form a major component of the fungal biota in forests dominated by Pinaceae, Fagaceae, Nothofagaceae, and Eucalyptus. Some species have been used extensively in experimental greenhouse and field studies of ectomycorrhizae. North American, European, and South American systematic treatments of Laccaria exist, and relatively much is now known about various aspects of the groups diversity and biology. However, knowledge of the group from Australasia is poor, identification tools and a world-wide taxonomic treatment do not exist, and further understanding of the biology of the Laccaria - Hydnangium group (e.g., relationships among species and overall diversity, geographic distribution, and host specificity on a global scale) remains stalled. This project address these critical questions by: (1) undertaking fieldwork in Australasia to complete sampling of ecological diversity, including studies of host tree specificity; (2) developing a rigorous classification of species relationships based upon DNA sequence data from both nuclear ribosomal markers and single-copy genes; (3) constructing web-based species-identification keys; and (4) completing a world monograph for the group that will be available in hard-copy and over the web. Collaboration and training are key aspects of this project. A postdoctoral associate will be involved with all aspects of the project, and the undergraduate student interns will gain valuable experience in collections-based research. Collaborators and their students in Australia, New Zealand, and Papua New Guinea will participate in field work. The resulting monograph will be produced both in hardcopy and as a web-based tool with images and descriptive data linked to the phylogeny. Hard copy quick references (so-called "rapidFungi field guides") and other identification tools for particular geographic regions will also be produced, as these are popular and useful for students, citizen scientists, park rangers, and ecotourists. The data will be integrated into public education programs at the Field Museum that focus on biodiversity; including inclusion in the museum's electronic field-trip program.