Assessment Notes

Justification

Rubroboletus pulcherrimus is an uncommon bolete known from northern California and the Pacific Northwest. Most collecting sites are from old growth forests, in coastal habitats. R. pulcherrimus (as Boletus pulcherrimus) is listed as a sensitive species by the USDA Forest Service (Castellano et al. 1999), and subjected to strategic surveys, yet still has a low number of known records. This species is listed on the Washington Natural Heritage Program List of Rare Macrofungi as a S1. It is relatively commonly reported from California. This is a large, brightly coloured species, and given its high detectability it is conservatively estimated that there are only up to 50-100 times more individuals than the approximately 250 records known based on Dahlberg and Mueller (2011) methodology, resulting in a precautionary population size of around 12,500-25,000 mature individuals in a single subpopulation. It is considered that the species' population is decreasing due to coastal development and logging in its primary habitat. Thus the species approaches, but doesn't meet the thresholds for consideration as threatened and is assessed as Near Threatened.

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Taxonomic notes

Until the past decade, the nomenclature and taxonomy of California’s ‘Satan’s Boletes’ was somewhat confounded. The name Boletus (Rubroboletus) eastwoodiae was misapplied to this species; what we now know as Rubroboletus eastwoodiae went by the misapplied name Boletus satanas. Thiers and Halling (1976) described Boletus pulcherrimus as a new species, and follow-up work has shown that B. satanas is strictly a European species, and the correct name for the Californian oak-associated Satan’s Bolete is B. eastwoodiae. More recently, these species were transferred to the genus Rubroboletus.

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Geographic range

This species occurs on the coast of California, USA, from Salt Point in Sonoma County, north to the Olympic Peninsula in Washington. It is also found in lower elevation forest in the Klamath Range, and western Cascades north through Washington into south-central British Columbia, Canada. It has been reported from New Mexico, Arizona, and there has been one observation from Michoacan, Mexico. These collections should be critically compared with Californian material, and with Rubroboletus haematinus; they are more likely conspecific with the latter species and are excluded from this assessment.

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Population and Trends

Rubroboletus pulcherrimus is currently known from c.40 sites, over a widespread area. Most Californian records are from protected coastal forests (in state and National Parks). Although it doesn't appear to be restricted to old growth forests, it has a strong preference for them. R. pulcherrimus (as Boletus pulcherrimus) is listed as a sensitive species by the USDA Forest Service (Castellano et al. 1999), and subjected to strategic surveys, yet still has a low number of known records. While it is rare to uncommon in Oregon and Washington State, there are 50 records (MyCoPortal 2024) from California and a large majority of the over 200 observations reported on iNaturalist (2024) are from California. This is a large, brightly coloured species. Given its high detectability it is conservatively estimated that there are only up to 50-100 times more mature individuals than the currently known number of records (250) (using the methodology of Dahlberg and Mueller 2011), resulting in a precautionary population size of around 12,500-25,000 mature individuals in a single subpopulation. It is considered that the species' population is decreasing due to coastal development and logging in its primary habitat.

Population Trend: Decreasing

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Habitat and Ecology

It is ectomycorrhizal with conifers, likely restricted to true firs (Abies) and hemlock (Tsuga). It grows in soil or duff, often in dense, mid-to-late seral stage and old growth forests. Fruiting is in late summer and fall, rarely in winter or spring.

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Threats

The main threats to this species are loss of habitat due to coastal development and logging of mature forests.

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Conservation Actions

Many localities are known from protected lands, but some occur on USFS land, where logging should be prohibited in areas where this species occurs. Rubroboletus pulcherrimus (as Boletus pulcherrimus) is listed as a sensitive species by the USDA Forest Service (Castellano et al. 1999), and subjected to strategic surveys. This species is listed on the Washington Natural Heritage Program List of Rare Macrofungi as a S1. Surveys to better document this species' distribution and population trends are needed. Additionally, habitat data should be noted when this species is found as it may be restricted to mature and old growth forests.

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Use and Trade

No use/trade is known.

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Source and Citation

Mueller, G.M. & Siegel, N. 2025. Rubroboletus pulcherrimus. The IUCN Red List of Threatened Species 2025: e.T273227629A273244416. Accessed on 20 November 2025.

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