Three hundred sixty-one species are currently reported from Yellowstone National Park. We found 72% of the total number of species in Engelmann spruce forests and 57.1% of the total number in Douglas fir forests, compared to 41.8% in lodgepole pine sites, including two talus slopes, and 36.3% in lodgepole/whitebark pine sites; 29.1% of the species were restricted to the old moist Douglas fir and spruce forests that have not burned for at least 300 years. Since about 80% of the forests in Yellowstone National Park are seral and climax lodgepole pine forests, and 8% are considered moist forests, the lichen distributions illustrate the importance of the old Douglas fir and spruce forest sites for lichen diversity in the park. Species with thalli large enough to identify are beginning to recolonize substrate burned in the 1988 fires.

Key words: ecology, lichens, Yellowstone National Park