Assessment Notes

Justification

Xerocomellus amylosporus has been recorded in coastal and Coast Range forests, the Sierra Nevada and Cascade Range of California north throughout the Pacific Northwest into southern British Columbia, Canada, and east to the northern Rocky Mountains. Although occurring over a widespread area, its reported localities are patchy. This species has a preference for, and may even be restricted to, mature and old growth forests. Being a poorly known species, and often misidentified as X. chrysenteron, records and trends of this species are insufficient to estimate population size and trends with high confidence. However, given its broad distribution, its population size may be relatively large and mostly stable across its range. Based on current information, it is assessed as Least Concern.

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Taxonomic notes

Collections have been misidentified as Xerocomellus (Boletus) chrysenteron and/or X. (Boletus) truncatus.

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Geographic range

Xerocomellus amylosporus has been recorded in northern California, USA from coastal and Coast Range forests, the Sierra Nevada and Cascade Range, north throughout the Pacific Northwest into southern British Columbia, Canada, and east to the northern Rocky Mountains.

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Population and Trends

Although occurring over a widespread area, its reported localities are patchy. This species has a preference for, and may even be restricted to mature and old growth forests. Being a poorly known species, and often misidentified as Xerocomellus chrysenteron, records and trends of this species are lacking. However, given its broad distribution, its population size may be relatively large and mostly stable across its range.

Population Trend: Stable

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Habitat and Ecology

This is an ectomycorrhizal species, apparently associating with conifers; especially Picea sitchensis and Abies spp. The type collection was described as “gregarious under Alnus rubra” (Smith 1965), however most recent collections come from sites without Alnus (Frank et al. 2020, N. Siegel field observations). Many recent collections have come from mature and old growth forests, however, it is not known if it is restricted to such forests.

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Threats

No specific threats have been identified with regard to this species at this time.

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Conservation Actions

No specific conservation actions is needed with regard to this species at this time. Detailed habitat notes with any new observations of this species are needed to describe habitat limitations, including information on tree association and if it requires mature or old growth forests to fruit.

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Use and Trade

This species is edible, and occasionally collected for food.

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Source and Citation

Mueller, G.M. 2025. Xerocomellus amylosporus. The IUCN Red List of Threatened Species 2025: e.T273196418A273244261. Accessed on 23 November 2025.

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