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

Gastroboletus amyloideus Thiers

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Scientific name
Gastroboletus amyloideus
Common names
IUCN Specialist Group
Mushroom, Bracket and Puffball
Assessment status
Proposed by
Noah Siegel
Comments etc.
Noah Siegel

Assessment Notes

Taxonomic notes

Described from a collection made at Yuba Pass in Sierra County, California, USA (Thiers & Trappe 1969).  The genus Gastroboletus accommodates a number of species with semisequestrate to sequestrate fruitbodies. These morphological forms have evolved multiple times, within different genera of boletes. Some of these species have been transferred to their ancestral genera; whiles others remain in limbo. Preliminary data shows that Gastroboletus amyloideus and G. vividus form a close-knit group with Boletus smithii (J. Frank pers. comm.). More work is needed on these species to delimit species concepts.

Why suggested for a Global Red List Assessment?

Gastroboletus amyloideus is a species known from 28 collections, and ten locations in the high elevation forests on the Sierra Nevada and southern Cascade Range in California and Oregon. Only three collections have been made since 1984, but mare data is needed, and historic sites need to be revisited before this species is assessed, because the decline of reports coincides with H.D. Thiers and W. B. Cooke no longer collecting in the California mountains. Therefore, I recommend listing it as Data Deficient (DD).

Geographic range

Known from high elevation forests in the Sierra Nevada mountains of California, USA, north into the southern Cascade Range in southern Oregon.

Population and Trends

Currently known from 28 collections, from ten locations (nine of which are in California); only three collections have been made since 1984 (Siegel et al. 2019). However, it is unknown if the drop off in collections is from a decline in this species; or more likely, H.D. Thiers and W. B. Cooke no longer collecting in the California mountains (MyCoPortal 2020). Historic sites should be revisited and appropriate habitat surveyed before trends and populations are assessed.

Population Trend: Uncertain

Habitat and Ecology

Solitary, scattered or in small clusters; fruitbodies forming underground, typically remaining buried, or occasionally emerging from duff when mature. Ectomycorrhizal, associated with Pinaceae, especially Red Fir (Abies magnifica) and Lodgepole Pine (Pinus contorta subsp. murrayana) in high elevation montane forests in the Sierra Nevada and Southern Cascade Range. Fruiting in summer (following monsoonal rains) and fall (Siegel et al. 2019). This species is likely dependent on mycophagy (primarily eaten by small mammals) for spore dispersal.

Temperate Forest


Prolonged droughts and decades of fire suppression have drastically altered the high Sierra Nevada forests, leading to thicker, denser, Abies dominated forests. As a result, hotter, stand replacing fires (rather than patchwork and understory burns) are commonplace, altering appropriate habitat drastically, and making it ill-suited for this species.

Increase in fire frequency/intensityDroughts

Conservation Actions

No specific conservation actions has been identified with regards to this species at this time.

Research needed

Modern taxonomic work is needed on this species; does it differ from Gastroboletus vividius? Historic sites should be revisited and appropriate habitat surveyed for this species.

TaxonomyPopulation size, distribution & trendsPopulation trends

Use and Trade

None known.


Desjardin, D.E., Wood, M.G and Stevens, F.A. 2015. California Mushrooms: The Comprehensive Identification Guide. Timber Press, Portland, OR.

Nouhra, E. and Castellano, M.A. 1995. NATS truffle and truffle-like fungi 3: Gastroboletus Dinoffii sp. nov. Mycotaxon. 55:179-183

Siegel, N., Vellinga, E.C., Schwarz, C., Castellano, M.A. and Ikeda, D. 2019. A Field Guide to the Rare Fungi of California’s National Forests. Bookmobile: Minneapolis, MN. 313 p.

Thiers, H.D. 1975. California Mushrooms – A Field Guide to the Boletes. Hafner Press.

Thiers, H.D. and Trappe, J.M. 1969. Studies in the genus Gastroboletus. Brittonia. 21(3):244-254

MyCoPortal. 2020. Mycology Collections Portal. Available at: http://mycoportal.org

Country occurrence

Regional Population and Trends

Country Trend Redlisted