Assessment Notes

Justification

Gastroboletus ruber is currently known from around 50 localities, mostly in the Pacific Northwest. There are six known subpopulations in California, but there have been no new records here since 1980 although research is needed to determine whether this is evidence of decline or simply an artefact of reduced survey effort. It is uncommon based on reports, but appears to be under-reported due to the summer or early fall fruiting, at high elevation localities. However, the population appears stable in the Pacific Northwest. It is tentatively assessed as Least Concern (LC) on the basis that the population is stable at least in the majority of its range.

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Taxonomic notes

Described as Truncocolumella rubra (Zeller 1939), this species was later transferred to the genus Gastroboletus (Cázares and Trappe 1991). 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, while others remain in limbo. The Gastroboletus ruber linage belongs with a group of red-pored boletes, and will be transferred soon (J. Frank et al. in ed.).

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Geographic range

This species is known mostly from high-elevation locations in the northern Sierra Nevada of California, and mid- to high-elevation locations in the Cascade Range in Oregon and Washington, USA.

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Population and Trends

The population appears to be stable in the northern part of the range; a number of observations have been made by casual observers (iNaturalist 2020) in recent years. Also it is considered to be "common in the Cascades of Washington at the right time of year" (S. Adams and J. Ammirati pers. comm.). There are currently six known California localities; but no new collections have been made here since 1980 (Siegel et al. 2019). Historic Californian localities should be revisited, as the decline of reports coincide with H.D. Thiers and W. B. Cooke no longer collecting in the area (MyCoPortal 2020).

Population Trend: stable

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Habitat and Ecology

It can be found as a solitary fruitbody, scattered or in small clusters, with fruitbodies forming underground and erupting from duff, but typically remaining partially buried when mature. It is ectomycorrhizal, associated with Pinaceae; especially mountain hemlock (Tsuga mertensiana) and fir (Abies spp.). Fruiting is in summer and early fall, typically after thunderstorms or summer rains in mid to high elevation forests. This species is likely dependent on mycophagy (primarily eaten by small mammals) for spore dispersal.

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Threats

Prolonged droughts and decades of fire suppression have drastically altered the high sierra forest, leading to thicker, denser, Abies-dominated forest. 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.

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Conservation Actions

No specific conservation actions have been identified with regards to this species at this time. There is a need to revisit historic localities in California and report the presence or absence of Gastroboletus ruber.

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Use and Trade

No use/trade is known.

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Source and Citation

Siegel, N. 2021. Gastroboletus ruber. The IUCN Red List of Threatened Species 2021: e.T198479622A198489708. https://dx.doi.org/10.2305/IUCN.UK.2021-2.RLTS.T198479622A198489708.en .Downloaded on 29 September 2021

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• Country occurrence