Assessment Notes

Justification

Choiromyces alveolatus is a widespread, but uncommon hypogeous fungus in western North America; occurring from near sea-level to subalpine forests. It produces sporophores from early spring into fall; most common in spring; typically buried quite deep in mineral soil. Currently it is known from about 30 disjunct subpopulations; mostly in California, but with nine collecting sites from Oregon, and single sites in Washington, Idaho, Wyoming and Utah. While some parts of its original range have probably been lost through development and the remaining habitat is probably declining in quality, its rate of population decline is not thought to be rapid enough to trigger listing under criterion A so it is assessed as Least Concern.

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Geographic range

This species is widespread in western North America; but rarely collected. It is known from the central coast, the Sierra Nevada and Cascade Range in California, USA, north into Oregon and from solitary sites in Washington, Utah (not mapped), Wyoming (not mapped) and Idaho (Siegel et al. 2019, MyCoPortal 2024).

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Population and Trends

This species is currently known from about 30 disjunct subpopulations; mostly in California, but with nine sites in Oregon, and single sites in Washington, Idaho, Wyoming and Utah (Siegel et al. 2019). This species is probably more common than current records indicate, but due to the cryptic nature (hypogeous sporophore producing, and often deep in soil), it is under-reported. Six collections were made in California during the 2011-2013 USFS Mt Shasta California Survey and Manage mushroom surveys, and an additional collection was found during the 2019 USFS Rare Fungal Species workshop at Yuba Pass in California (N. Siegel, unpublished). Their are 15 observations (five of which are research grade) on iNaturalist (2024). While some parts of its original range has likely been lost through development and the remaining habit likely declining in quality (see threats section), its rate of population decline is not thought to be rapid enough to trigger listing under criterion A.

Population Trend: Decreasing

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Habitat and Ecology

It is hypogeous, solitary or scattered in ‘nests’, usually buried quite deep in the mineral soil. It is an ectomycorrhizal species, growing with Pinaceae, especially Red Fir (Abies magnifica). It occurs from near sea-level to subalpine forests; producing sporophores from soon after snow melt in early spring, through summer, or into fall.

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Threats

Most recent collections have been made in high elevation, old growth Red Fir (Abies magnifica) forests; a number of historic collections come from the Sierra Nevada foothills, in areas that have been largely developed. Continued loss of habitat, declines in old growth forests and hotter, stand replacing fires may be detrimental to this species.

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Conservation Actions

No specific conservation actions have been identified with regard to this species at this time. Continued surveys for this species in western North America are needed to assess its range and population trends.

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Use and Trade

This species is edible, but due to its scarcity, rarely collected.

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Source and Citation

Siegel, N. & Mueller, G.M. 2025. Choiromyces alveolatus. The IUCN Red List of Threatened Species 2025: e.T273188534A273188866. Accessed on 25 November 2025.

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• Country occurrence