Arbuscular mycorrhizal (AM) fungi improve plant growth and play an important role in ecosystem processes, but are vulnerable to human disturbance. This project seeks to better evaluate and understand the range of diversity of AM fungi by isolating, describing, and culturing species from a well-defined community type, the native grassland communities of North America. Four grassland systems will be studied: tallgrass prairie, shortgrass prairie, desert grasslands and California grasslands. Morphological and molecular data will be combined to describe new AM species, thereby establishing a new standard for species descriptions. Phylogenetic relationships amongst species will be clarified, thus advancing knowledge of fungal systematics. Relationships between plant and AM fungal diversity will be tested at several spatial scales, which in turn will provide better estimates of how much biodiversity is missing across ecosystem types. Sampling design includes comparisons of disturbed and undisturbed sites, so estimates of the number of species that might be at risk from habitat degradation can be obtained. A product of this research will be greatly expanded molecular and biogeographic databases. Also, pure cultures of fungi native to grasslands will be available for use by scientists, teachers, students, and commercial enterprises.