Assessment Notes

Justification

Balsamia nigrans is a small, hypogeous fungus with a coarsely warted black exterior and a firm, solid whitish gleba, marbled with white veins. A rare species, or at least rarely reported, it is currently known from fewer than 30 collections from 17 disjunct subpopulations from southern California, north through the Sierra Nevada foothills, into the Klamath Mountains in Oregon, with old reports from Arizona (two collections) and Utah (one collection). It is difficult to estimate confidently its population size because it is probably under-recorded through parts of its range, but even assuming that there are 500-1,000 total sites, each with 5-10 mature individuals, the estimated population size is 2,500-10,000 mature individuals distributed in small, disjunct, subpopulations of fewer than 1,000 mature individuals. Loss and degradation of of habitat is considered to be leading to a decrease in population size. Therefore, the species is assessed as Vulnerable.

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Geographic range

This species occurs in disjunct subpopulations; a single site in the mountains in Los Angeles County, California, USA; from low to mid elevations in the south-central to north-central Sierra Nevada in California; a single site in the Klamath Mountains in California; and scattered sites in the Klamath and Coast Range in Oregon. NatureServe Explorer (2024) also lists three additional records, two from Arizona and one from Utah (these are not mapped here).

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Population and Trends

Southworth et al. (2018) reports 23 collections, from 17 sites, seven of which are from more than 30 years ago. There are 20 records in GBIF (2024), of which 10 are from more than 30 years ago. Revisits to some historic locations were successful in relocating this species. The population and trend of this species are hard to assess, as limited surveying has been done to locate subpopulations in much of its range. In addition, the cryptic nature (hypogeous fruiting, dark colours) and growth in areas with sporadic rainfall and limited mycological work (Sierra Nevada Foothills), have probably lead to under-reporting of this species.

It is ranked as G3 (Vulnerable) by NatureServe (NatureServe Explorer 2024). It is difficult to estimate confidently its population size because it is probably under-recorded through parts of its range, but even assuming that there are 500-1,000 sites, each with 5-10 mature individuals, the estimated population size is 2,500-10,000 mature individuals distributed in small, isolated subpopulations of fewer than 1,000 mature individuals. Loss and degradation of habitat is considered to be leading to a decrease in population size.

Population Trend: Decreasing

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Habitat and Ecology

It is hypogeous, solitary, scattered, or sometimes clustered, buried in duff or soil. It is presumed to be ectomycorrhizal, associated with Pinaceae; especially Douglas-fir (Pseudotsuga menziesii) and Jeffrey Pine (Pinus jeffreyi). Most collections come from low to mid-elevations, with one site in the southern Sierra Nevada, made in high elevation Red Fir (Abies magnifica) forest. It has also been found under oak (Quercus spp.). This species is dependent on mycophagy (primarily eaten by small mammals) for spore dispersal.

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Threats

Loss of habitat due to development and urban sprawl in the Sierra Nevada foothills is thought to be impacting this species.

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Conservation Actions

This species in included on the US Forest Service sensitive species list as part of the Northwest Forest Plan (Castellano et al. 1999). Additional surveys for this species are needed in suitable habitat in localities between disjunct subpopulations, to see if the range is more continuous than currently known.

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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. Balsamia nigrans. The IUCN Red List of Threatened Species 2025: e.T273188403A273188861. Accessed on 22 November 2025.

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• Country occurrence