R-L categories correct, but text here does not match final assessment. Updated version will be published in IUCN´s Red List June or Nov 2019.
Stereopsis humphreyi is a peculiar saprotrophic very rare fungal species, occurring in coastal old-growth conifer forests from Southeast Alaska southwards to central Oregon. The known sites are scattered along the coast from central Oregon northwards to Sitka in Alaska. The species is conspicuous, but has only been reported from 25 locations. The extent of occurrence is bigger that 20,000 sq km., even though the species is only known from a narrow strip bordering the ocean. Its habitat, in wet mucky places near creeks and ponds of coastal old-growth forests are declining due to clear cutting and forest management. It is assessed as Near Threatened based on having a small, largely unrecorded population along the coast with a total of fewer than 300 locations in a habitat that is declining due to ongoing forest management.
Stereopsis humphreyi is a member of the Agaricales, whereas the type species of the genus is unrelated, and placed (with other species in Stereopsis) in its own order, Stereopsidales (Sjøkvist et al. 2012; 2014), close to the Phallomycetidae. This implies that Stereopsis humphreyi has to be moved into its own genus.
Stereopsis humphreyi takes an isolated position within the Agaricales, and is surrounded by gilled mushrooms (Moncalvo et al. 2002). It does not have close relatives that share the simple, non-gilled hymenophore. The records of Stereopsis humphreyi from interior China are not considered to belong to the same species as the western American species.
Stereopsis humphreyi is distributed from central coastal Oregon in the U.S.A. northwards via Haida Gwaii [formerly known as Queen Charlotte Islands] in Canada to southeast Alaska. All locations are at sea level and coastal.
The species is known to occur or to have occurred in around 25 locations that occur scattered along the coast from central Oregon to Southeast Alaska. The species has repeatedly been found over the span of 70 years on some of these locations (e.g. at the type locality). In the southern part of its area, available habitat is spotty and does not form a continuous belt. Habitat on Haida Gwaii (in the northern part of its occurrence) is available and forms a more continuous zone along the coast. Data on occurrence on the coast of mainland British Columbia are not available.
The number of locations is assessed not to exceed 300 considering unrecorded locations along the coast. There are typically only a few fungal mycelia of S. humphreyi at each location, hence the estimated total number of mature individuals does not exceed 15,000 (c.f. Dahlberg & Mueller, 2011).
Population Trend: Decreasing
Stereopsis humphreyi’s life-form is presumed to be saprotrophic growing on needle debris in coastal lowland old-growth coniferous forests with Sitka spruce (Picea sitchensis), Western red cedar (Thuja plicata) and Western hemlock (Tsuga heterophylla), in wet, muddy, mossy places (Redhead & Reid 1984; Kroeger et al. 2012; Siegel, pers. comm). It stands out in the dark forest because of its white fruitbodies that resemble angel wings on a stem. Like other litter- and ectomycorrhizal fungi, individual mycelia are perennial and persist for many years (Dahlberg & Mueller, 2011).
The extent of old growth forest in the Pacific Northwest of North America has declined 90% in the last century (Society of American Foresters 1984, Haynes 1986), and coastal forest in particular has been heavily logged. Lumber operations in British Columbia started in the 1850s, those in the USA in the late 1800s, but clear cutting started in earnest early in the 20th century, and has been ongoing since. The existing sites where this species occurs are scattered, some are in protected areas such as National Parks in the U.S.A. or National Park Reserve or Provincial parks in Canada.
Protection of known sites.
The taxonomy of this species has to be settled, and the identity of the Chinese collections to be established. The nutritional mode is not known, but it is expected judging from the phylogenetic position, to be saprotrophic (see Moncalvo et al., 2002).
The species is not known to be used.
Burt, E.A. 1914. The Thelephoraceae of North America. II. Craterellus. Annals of the Missouri Botanical Garden. 1: 327-349.
Dahlberg A & Mueller G. 2011. Applying IUCN red-listing criteria for assessing and reporting on the conservation status of fungal species. Fungal Ecology 4: 1-16
Haynes, T.W. 1986. Inventory and value of old-growth in the Douglas-fir region. PNW-RN 437. U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station, Portland, OR.
Kroeger, P., Kendrick, B., Ceska, O. & Roberts, C. 2012. Outer spores: Mushrooms of Haida Gwaii.
Moncalvo, J.M. et 13 al., 2002. One hundred and seventeen clades of euagarics. Molecular phylogenetics and evolution 23: 357–400.
Sjøkvist, E., Larsson, E., Eberhardt, U., Ryvarden, L. & Larsson, K.H. 2012. Stipitate stereoid basidiocarps have evolved multiple times. Mycologia 104: 1046–1055.
Sjøkvist, E., Pfeil, B.E., Larsson, E. & Larsson K.H. 2014. Stereopsidales - A new order of mushroom-forming fungi. PLOSone 9: 9e95527.
Society of American Foresters. 1984. Scheduling the harvest of old growth : Old-growth forests in the Pacific Northwest : a position of the Society of American Foresters and Report of the SAF Task Force on Scheduling the Harvest of Old-Growth Timber. . Bethesda, MD.
Redhead, S.A. & Reid, D.A. 1983. Craterellus humphreyi, an unusual Stereopsis from western North America. Canadian Journal of Botany 61:3088–3090.