Suillus subalpinus was described by Moser (1997) from subalpine forests in Grand Teton National Park, Wyoming, USA. Basidiomata of this species are glutinous at first, becoming viscid; the cap is white at the margin with a gray brown to vinaceous brown center; the entire cap surface may become golden brown to light brown in age. The stipe lacks a veil, and has abundant glandular dots that are white at first, becoming reddish brown in age. The species resembles S. brunnescens Smith & Thiers, but differs in that S. subalpinus lacks a veil (Moser 1997).
An unpublished phylogenetic analysis supports S. subalpinus as genetically distinct from other North American Suillus species associated with 5-needled pines (N. Nguyen & E. Vellinga, personal communication).
Suillus species form ectomycorrhizal symbioses with the roots of woody plant species. Suillus species are unusual among ectomycorrhizal fungi in their level of host specificity; they appear to be associated almost exclusively with the plant family Pinaceae (Bruns et al. 2002) as well as a small number of achlorophyllous mycoheterotrophic ericaceous plants (Dahlberg & Finlay 1999), and some species appear to be associated with only one or a limited number of plant species (Bruns et al. 2002). Suillus subalpinus is only known to occur with a single host tree species, Pinus albicaulis, which is severely threatened by a non-native fungal disease (white pine blister rust), an insect pest (mountain pine beetle), climate change and the effects of fire suppression (Schwandt 2006). Pinus albicaulis is rapidly declining in most of its geographical range (Schwandt), and is categorized in the IUCN Red List of Threatened Species as Endangered (A4ace, ver 3.1).
Given the host specificity of S. subalpinus, the small likelihood of occurring with other hosts in the event of loss Pinus albicaulis (based on the lack of observed field occurrence with other hosts), and rapid declines in the population of Pinus albicaulis, S. subalpinus should be considered for a Global Fungal Red List Assessment.
Suillus subalpinus was originally described from Grand Teton National Park, Wyoming, USA, and appears to be restricted to the northern Rocky Mountain subalpine zone in association with whitebark pine (Pinus albicaulis). A collection of S. subalpinus from Camp Arnold, Eatonville, Washington, USA was verified by C. Cripps, and the species has been reported on Mushroom Observer from the Wind River Range, Wyoming.
The geographic range of the ectomycorrhizal host plant Pinus albicaulis—here presumed to represent the maximum potential range of Suillus subalpinus—is summarized below from the IUCN Red List of Threatened Species species page for P. albicaulis (Mahalovich & Stritch 2013):
Whitebark Pine is distributed from 37° to 55°N latitude and from 128° to 107°W longitude, with the total global extent of occurrence estimated at 337,067 km2 (estimated 190,067 km2 in Canada, 147,000 km2 in the USA), and estimated global area of occupancy in excess of 2,000 km2. It is found in the North American coastal mountain ranges (British Columbia Coast Ranges, Cascade Range, Sierra Nevada) and in the Rocky Mountains from eastern British Columbia and western Alberta southward to the Wind River and Salt River Ranges, Wyoming, occurring in subalpine elevations to nearly treeline, up to “3,050 to 3,660 m in the Sierra Nevada and northwestern Wyoming, 2,590 to 3,200 m in western Wyoming and as low as 900 m in the northern limits of its range in British Columbia.” Outlying populations are reported in the Sweetgrass Hills in north-central Montana, the Blue and Wallowa Mountains of northeastern Oregon, and “in small, isolated ranges in northeastern California, south-central Oregon, and northern Nevada (Arno and Hoff 1990).”
Both Suillus subalpinus and the similar-looking S. brunneus are not widely represented in available herbarium records (http://www.mycoportal.org). Two collections from Wyoming are cited in the original description of S. subalpinus; an additional collection from Wyoming is found in MycoPortal, and collections from Wyoming and Washington are reported in Mushroom Observer (http://www.mushroomobserver.org). S. subalpinus is also found in northern Montana and southern British Columbia (C.L. Cripps, personal communication).
Population Trend: Uncertain
Suillus subalpinus appears to be an obligate ectomycorrhizal symbiont of whitebark pine (Pinus albicaulis) in subalpine forests in the northern Rocky Mountains. Although the original description of the species (Moser, 1997) states that S. subalpinus occurs with both limber pine (Pinus flexili) and whitebark pine, later studies (Moser, 2004; Cripps & Antibus, 2011) state that the species is restricted to Pinus albicaulis. P. albicaulis the only stone pine (Pinus sect. Strobus subsect. Cembrae) that occurs in North America (Farjon 2010).
The only known mycorrhizal host of this species is severely threatened by a non-native fungal disease, white pine blister rust (Cronartium ribicola).
IUCN Red List (http://www.iucnredlist.org/details/39049/0)
Consider host vs. fungal generation time: host 50% decline over past 100 to future 80 years—> IUCN endangered. Correct for difference in generatio tims.
Control of white pine blister rust infection of whitebark pine.
ex situ conservation
limber pine inoculation
Arno, S.F. and R.J. Hoff. 1990. Pinus albicaulis Englem. In: R.M. Burns and B.H. Honkala (eds), Silvics of North America, Agriculture Handbook 654, pp. 268-279. USDA Forest Service, Washington, DC.
Bruns, T.D., M.I. Bidartondo and D.L. Taylor. 2002. Host specificity in ectomycorrhizal communities: What do the exceptions tell us? Integr. Comp. Biol. 42(2): 352-359.
Cripps, C.L. and R.K. Antibus. 2011. Native Ectomycorrhizal Fungi of Limber and Whitebark Pine: Necessary for Forest Sustainability? In: Keane, Robert E.; Tomback, Diana F.; Murray, Michael P.; and Smith, Cyndi M., eds. 2011. The future of high-elevation, five-needle white pines in Western North America: Proceedings of the High Five Symposium. 28-30 June 2010; Missoula, MT. Proceedings RMRS-P-63. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station. 376 p. Online at http://www.fs.fed.us/rm/pubs/rmrs_p063.html.
Dahlberg, A. and R.D. Finlay. 1999. Suillus. pp. 33-64 in: Cairney, J.W.G. and S.M. Chambers, eds. Ectomycorrhizal Fungi: Key Genera in Profile. Berlin: Springer.
Farjon, A. 2010. A Handbook of the World’s Conifers. Leiden, Netherlands: Koninklijke.
Mahalovich, M. & Stritch, L. 2013. Pinus albicaulis. The IUCN Red List of Threatened Species.
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