• Proposed
  • 2Under Assessment
  • 3Preliminary Assessed
  • 4Assessed
  • 5Published

Xerocomellus amylosporus (A.H. Sm.) J.L. Frank & N. Siegel

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Scientific name
Xerocomellus amylosporus
(A.H. Sm.) J.L. Frank & N. Siegel
Common names
IUCN Specialist Group
Mushroom, Bracket and Puffball
Assessment status
Proposed by
Noah Siegel
Comments etc.
Noah Siegel

Assessment Notes

Taxonomic notes

Originally described as Porphyrellus amylosporus (Smith 1965) from a collection made in Idaho, USA, it was invalidly transferred it into the genus Tylopilus (the basionym not cited) by Smith & Smith (1973). Wolfe in his studies of Porphyrellus (1986) transferred it into the genus Boletus. Based on genetic and morphological studies (Frank et al. 2020) it was transferred into the genus Xerocomellus. Gastroboletus xerocomoides (Thiers and Trappe 1969) was found to be a synonym of X. amylosporus (Frank et al. 2020).

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

Why suggested for a Global Red List Assessment?

Xerocomellus amylosporus is an uncommon but widespread bolete in western North America.

It appears to have a preference for mature and old growth forests, but based on current information, we do not know if it is restricted to such habitat. Until a determination can be made on habitat preferences, we recommend listing it as Data Deficient (DD).

Geographic range

Occurring in northern California, USA in 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.

Population and Trends

Although occurring over a widespread area, populations appear to be 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.

Population Trend: Uncertain

Habitat and Ecology

Ectomycorrhizal, apparently 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 locations 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.

Temperate Forest


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

Conservation Actions

No specific conservation actions is needed with regards to this species at this time

Research needed

Detailed habitat notes with any new observations of this species to describe habitat limitations; tree association and if it needs mature or old growth forests to fruit.

Population size, distribution & trendsLife history & ecology

Use and Trade

This species is edible, and occasionally collected for food.

Food - human


Frank, J., Siegel, N., Schwarz, C., Araki, B. and Vellinga, E. 2020. Xerocomellus (Boletaceae) in western North America. Fungal Systematics and Evolution 6: 265-288.

Siegel, N. & Schwarz, C. 2016. Mushrooms of the Redwood Coast. Ten Speed Press: Berkeley, CA. 601 p.

Smith, A.H. 1965. New and unusual basidiomycetes with commentson hyphal and spore wall reactions with Melzer’s solution. Mycopathologia et Mycologia Applicata 26: 385–402.

Smith, H.V. and Smith, A.H. 1973. How to Know the Non-gilled Fleshy Fungi. William C. Brown, Dubuque, Iowa. 402 pp

Thiers, H.D. and Trappe, J.M. 1969. Studies in the genus Gastroboletus. Brittonia 21: 244-254.

Wolfe Jr., C.B. 1986. A numerical taxonomic analysis of Tylopilus subgenus Porphyrellus (Boletaceae). Nova Hedwigia 43(3-4): 515-523.

Country occurrence

Regional Population and Trends

Country Trend Redlisted