Assessment Notes

Justification

Aureoboletus citriniporus is an ectomycorrhizal bolete occurring in oak woodlands, especially with Coast Live Oak in the greater San Francisco Bay Area. Recent reports are mostly from the Bay Area and Santa Cruz. Historic collections come from the Sierra Nevada foothills (MyCoPortal 2020), but no recent records are reported (iNaturalist 2020, Mushroom Observer 2020). About c. 40 locations are currently known. Although limited data are available showing trends of this species, it has experienced population decline in the past due to habitat loss, and this decline is ongoing due to continued urbanisation, coupled with a continuing decline in habitat quality due to impact of sudden oak death on its host tree and impact of invasive grasses. Taken together these threats are causing a significant decline in the species, suspected to at least approach the thresholds for listing as Vulnerable. Thus, this species is assessed as Near Threatened.

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Taxonomic notes

Described as Boletus citriniporus (Halling 1977), from a California, USA, collection made in the Sierra Nevada foothills, it was later transferred to the genus Aureoboletus (Klofac 2010).

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Geographic range

The species is endemic to the western United States. Most records come from Santa Cruz County through the San Francisco Bay Area, north to Sonoma County, California, USA, with scattered records in the Sierra Nevada foothills, and it has also been reported from Corvallis, Oregon (N. Siegel pers. obs.). There is a single potential record has been reported from southern California (MycoPortal 2020).

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Population and Trends

The population is mostly centred from Santa Cruz County to Marin County, California, through the San Francisco Bay Area; an area that is a highly developed under urban sprawl. Other scattered reports come from the coastal California counties north to Humboldt County, the Sierra Nevada foothills, and a single location in Corvallis, Oregon. About 40 locations are currently known. Although limited data are available showing trends of this species, it is likely decreasing due to habitat loss, decline in its host tree due to disease, and decline in habitat quality due to invasive grasses.

Population Trend: decreasing

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Habitat and Ecology

It is ectomycorrhizal with oaks (Quercus spp.), especially Coast Live Oak (Quercus agrifolia). Typically it occurs in stands of oak with thick duff, or duff build-up, without a grassy or weedy under story. Fruiting is from fall into winter.

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Threats

Sudden oak death, caused by Phytophthora ramorum has been spreading through California’s oak woodlands, causing considerable mortality in some regions. Urban development has lead to significant loss of habitat, and invasive plants, especially grasses growing in oak woodlands are degrading the habitat.

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Conservation Actions

Additional oak woodlands in the Bay Area need protection. Better management, especially in control of invasive plants in oak woodlands is needed. Additional surveys for this species in southern California, and the Sierra Nevada foothills to better document its distribution and population size would enhance conservation efforts.

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Use and Trade

This species is edible, and occasionally collected for food.

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Source and Citation

Siegel, N. 2022. Aureoboletus citriniporus. The IUCN Red List of Threatened Species 2022: e.T217580565A217581804. https://dx.doi.org/10.2305/IUCN.UK.2022-1.RLTS.T217580565A217581804.en .Accessed on 4 August 2024

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• Country occurrence