Assessment Notes

Justification

Lactarius paulus is a small, sequestrate and hypogeous species with a white to pale yellow cap and reduced stipe, a gleba which is completely enclosed, and white latex and an acrid taste. It is only known from five sites, four around Yuba Pass in the northern Sierra Nevada and one in the central Sierra Nevada, in Stanislaus National Forest. It appears to occur in drier, east-side pine forest. The species has apparently not been recorded since the 1980's even though the area from where it has been recorded is frequently surveyed. Given that it is known from only two threat-based locations and has not been recorded in decades, the documented increase in fire frequency and intensity throughout the Sierra Nevada Mountains (Steel et al. 2023, Wang et al. 2024) could drive the species to extinction in a short time. Therefore, precautionarily it is assessed as Vulnerable D2

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Geographic range

Currently this species is only known from five sites at two threat-based locations, four around Yuba Pass in the northern Sierra Nevada, California, USA and one in the central Sierra Nevada, in Stanislaus National Forest.

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Population and Trends

Records in GBIF date from the 1980's (GBIF 2024) and there are no records of the species in MyCoPortal (2024). It apparently has not been recollected in nearly 40 years even though the area from where it has been recorded is frequently surveyed. Too little is known for a proper assessment of population or trends. Given that it is known from only two general locations and has not been recorded in decades, the documented increase in fire frequency and intensity throughout the Sierra Nevada Mountains (Steel et al. 2023, Wang et al. 2024) could drive the species to extinction in a short time.

Population Trend: Unknown

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Habitat and Ecology

This species is hypogeous, fruiting solitarily or scattered, buried under duff and in soil under pines (Pinus spp.) and fir (Abies spp.). It is ectomycorrhizal, associated with Pinaceae. Fruiting occurs in spring and early summer. This species is probably dependent on mycophagy (primarily eaten by small mammals) for spore dispersal.

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Threats

Climate change and droughts, along with forest management practices have made western forests, including the Central and Northern Serra Mountains highly susceptible to stand replacing forest fires (Steel et al. 2023, Wang et al. 2024).

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Conservation Actions

Improved forest management to reduce fire risk is needed, especially at known sites. Targeted surveys and revisiting known occurrences are needed as most collections are historic.

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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. Lactarius paulus. The IUCN Red List of Threatened Species 2025: e.T273195742A273247765. Accessed on 27 November 2025.

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• Country occurrence