Assessment Notes

Justification

Mycena hudsoniana is a rare snowbank species restricted to western montane forest with ample winter snowpack. Its habitat is being drastically affected by the changing climate, with warmer and drier winters that have elevated and lessened the average snowfall. Stoelinga et al. (2010) state that Cascade Range spring snowpack declined 23% during 1930-2007, while Fyfe et al. (2017) cite a 21.8% loss between 1982-1993 and 2000-2010, and models suggest that the rate of snowpack decline will increase substantially by the end of the century (Mote et al. 2005, 2018; Rhoades et al. 2018). As this species is restricted to snowbanks, a population decline of over 30% can be suspected to occur over the range of three generations (30 years) taking into account past and projected loss of suitable habitat. It is assessed as Vulnerable.

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Taxonomic notes

Rported collections from Minnesota and Alberta (MyCoPortal 2024) should be re-examined, as they may be misidentified. Field identification of Mycena species is in general impossible, and this species might have been overlooked, under sampled and/or misidentified.

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Geographic range

Mycena hudsoniana is known from mostly disjunct subpopulations in the Pacific Northwest USA, into Canada, and northern California in the southern Cascade Range.

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Population and Trends

Currently, this species is known from 14 sites in its range. Grey Mycena are difficult to identify, and are rarely reported, so this is likely to be more common than reported. However, some of the reports probably represent misidentifications. This is a snowbank species (Cooke 1955), restricted to western montane forest with ample winter snowpack. Its habitat is being drastically affected by changing climate with warmer and drier winters that have elevated and lessened the average snowfall. Stoelinga et al. (2010) state that Cascade Range spring snowpack declined 23% during 1930-2007 while Fyfe et al. (2017) cite a 21.8% loss between 1982-1993 and 2000-2010 and models suggest that the rate of snowpack decline will increase substantially by the end of the century (Mote et al. 2005, 2018; Rhoades et al. 2018). As this species is restricted to snowbanks, a population decline of over 30% can be suspected to occur over the range of three generations (30 years) taking into account past and projected loss of suitable habitat.

Population Trend: Decreasing

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Habitat and Ecology

The species is found solitary or scattered fruiting bodies in duff, typically fruiting on the edges of melting snowbanks in spring, often in montane forest. It is saprotrophic on duff and debris of conifers.

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Threats

Mycena hudsoniana is a rare snowbank fungus dependent on thick winter snowpacks to fruit. Snowbank fungi, unique to the western North American mountains, occur in areas with ample snowpack. They fruit in the spring and summer, as the snow melts and recedes. As the climate changes, warmer and drier winters have elevated and lessened the average snowfall. Climate change, continued loss of habitat, decline in area of old growth forests, and hotter, stand replacing fires are detrimental to this species. Snowpack decline in the western North American mountains has been well documented (Mote et al. 2005, 2018; Stoelinga et al. 2010; Zeng et al. 2018). Stoelinga et al. (2010) state that Cascade Range spring snowpack declined 23% during 1930-2007, and models suggest that the rate of snowpack decline will increase substantially by the end of the century (Rhoades et al. 2018).

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Conservation Actions

It will be important to protect areas with known subpopulations of Mycena hudsoniana from logging and development. Surveys to better document its habitat and refine understanding of its distribution and population size and trends are needed.

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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. Mycena hudsoniana. The IUCN Red List of Threatened Species 2025: e.T273197382A273243972. Accessed on 22 November 2025.

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• Country occurrence