Checklist and Ecology of the Agaricales, Russulales and Boletales in the alpine zone of the Rocky Mountains (Colorado, Montana, Wyoming) at 3000-4000 m a.s.l.

Previously, the Rocky Mountain alpine zone was a mycological blank spot. There have only been a few scattered records of macrofungi from this region and limited number of publications. This alpine survey covers the Beartooth Plateau in Montana/Wyoming for the North-central Floristic Region (lat 45°N) and the Front Range, San Juan Mountains, Sawatch Range for the Southern Floristic Region in Colorado (lat 36°-38°N), and reports over 165 species in 46 genera and 11 families (ca 1 500 collections). It is estimated that over 75% are known arctic-alpine macromycetes and the remainder are Rocky Mountain species. Of these, we estimate that 2-5% are new to science, 75% are new records for this Rocky Mountain alpine zone, and that over half will be new to Colorado or Montana/Wyoming. Approximately 56% are mycorrhizal species associated with Salix reticulata, S. arctica, S. planifolia, S. glauca, Betula nana = B. glandulosa, Dryas octopetala and Polygonum viviparum. Mycorrhizal species that occur with Betula are rare in the Rockies due to a paucity of this host. The most diverse mycorrhizal family is the Cortinariaceae with over 74 species, primarily of Inocybe and Cortinarius. Saprobic genera associate with a diversity of bryophytes or are terrestrial primarily in grassland; macrofungi on woody debris are rare. A greater diversity occurs in southern mountain ranges which are more diverse in geology and habitat. The southern extent of the Rockies at latitudes of 36-38°N likely includes the southernmost extent of certain Arctic-alpine fungi such as Arrhenia auriscalpium for the Northern hemisphere. Macrofungal fruitings are sparse compared to those in maritime arctic-alpine habitats due to a well-defined continental climate with drying winds, low relative humidity, periodic droughts, fire, strong diurnal temperature fluctuations and high elevations of 3 000-4 000 m. This report helps complete distributions of arctic-alpine fungi, and discusses the ecology of individual taxonomic groups in relation to other Arctic-alpine areas.