Originally described as a variety of Suillus tomentosus (Smith et al. 1965), from collections made near Priest Lake, Idaho, USA.
Based on morphology and genetic studies, elevated to species rank (Nguyen et al. 2017).
Suillus discolor is an uncommon ‘slippery jack’ with a creamy buff to cinnamon-brown or olive-brown cap, often covered with grayish fibrils when young, more extensively ochraceous to yellow in age. The pores are ochraceous to ocher-buff, and it has ochraceous cap flesh which slowly stains blue. It is very similar in appearance to Suillus tomentosus, but often dingier colored when young, and is associated with five-needle pines (not two- and three-needle pines like S. tomentosus). Currently known from two sites in California, two in Washington, and ~twelve in Idaho, and a single report from both Colorado and New Mexico, and reported from Montana and Wyoming.
Due to confusion with the common and better known species, Suillus tomentosus; the misidentification of records; and the uncertainty of tree association, I recommend listing as Data Deficient (DD) at this time. This should be revisited in a few years with additional data, as it may only be associated with pine species in peril.
Scattered through the Northern Rocky Mountains, and from high elevation, disjunct ‘sky islands’ south to New Mexico in the Rocky Mountains, and two location in Washington and California, USA. Distribution is patchy; occurring with five-needle pines.
Due to confusion with Suillus tomentosus, population and trends of this species remain largely unknown. Suillus discolor is associated with high elevation pine species under threat from White Pine Blister Rust (Cronartium ribicola), and likely the population is declining. However, it may be associated with Western White Pine (Pinus monticola) and the overall population, while declining, is still widespread enough to not be under immediate threat.
Population Trend: Uncertain
Solitary or scattered in soil, ectomycorrhizal with five-needle pines at high elevations. In California, one collection was associated was Limber Pine (Pinus flexilis), the other with Whitebark Pine (Pinus albicaulis), in dry subalpine/alpine forest on the eastern side of the Sierra Nevada, Montana and Wyoming collections were with Whitebark Pine. Data is lacking on other collections, and their pine associates. More data is needed to see if this species occurs with Western White Pine (Pinus monticola), or if it restricted to the high elevation five-needle pine species. Fruiting in summer and fall.
Populations of five needle pines are threatened by a non-native fungal disease, white pine blister rust (Cronartium ribicola) across much of the range of this species.
Protection of known populations.
Tree association of Suillus discolor; is it restricted to the high elevation ‘sky islands’ of five needle pines (ie. Pinus albicaulis, P. flexilis), or more widespread with P. monticola. Extent of population; which will include examining collections labeled Suillus discolor (most as S. tomentosus var. discolor), based on location and tree association are likely misidentified.
Cripps, C.L., Evenson, V. and Kuo, M. 2016. The essential guide to Rocky Mountain mushrooms by habitat. University of Illinois Press.
Mohatt K.R., Cripps, C.L. and Lavin, M.L. 2008. Ectomycorrhizal fungi of whitebark pine (a tree in peril) revealed by sporocarps and molecular analysis of mycorrhizae from treeline forests in the Greater Yellowstone Ecosystem. Botany 86: 14–25.
Nguyen, N., Vellinga, E.C., Bruns, T.D. and Kennedy, P. 2017. Phylogenetic assessment of global Suillus ITS sequences supports morphologically defined species and reveals synonymous and undescribed taxa. Mycologia 108:1216–1228.
Siegel, N., Vellinga, E.C., Schwarz, C., Castellano, M.A. and Ikeda, D. 2019. A Field Guide to the Rare Fungi of California’s National Forests. Bookmobile: Minneapolis, MN. 313 p.
Smith, A.H., Thiers, H.D. and Miller, O.K. 1965. The species of Suillus and Fuscoboletinus of the Priest River Experimental Forest and vicinity, Priest River, Idaho. Lloydia 28:120–138