Described as Martellia subalpina (Smith 1963) from a collection made near McCall, Idaho, USA; then transferred to the genus Gymnomyces (Trappe et al. 2002).
Phylogenetic research has shown that these hypogeous lineages have evolved multiple times, therefore they have since been transferred into the mostly epigeous genus Russula (Elliott & Trappe 2018). Based on an earlier name of Russula subalpinus, this species was described Russula orsonmilleri when transferred into Russula (Elliott & Trappe 2018).
These hypogeous Russula (Gymnomyces) are notoriously hard to identify to species, requiring diligent microscopic examination, and occasionally, the genetic fingerprint.
Russula orsonmilleri is a small to medium-sized, hypogeous fungus, likely restricted to mature and old growth fir forests. Currently known from five sites; one in Idaho, two in Oregon and two in California. There were fourteen collections made at one of the California sites (Swain Mountain) in July and August of 1994. Attempts should be made to locate other sites in the area.
Known from four locations in the southern Cascade Range in California and Oregon, USA, and the Type location in Idaho.
This species is currently known from five disjunct locations, although limited surveys have been carried out in similar habitat in between populations. During extensive hypogeous fungal work done at a location in northern California (Swain Mountain), there were fourteen collections made in July and August of 1994 (Siegel et al. 2019). As far as we know, no attempts to re-find it have been made at this location. This species may be restricted to old growth forests, which are in decline.
Population Trend: Uncertain
Hypogeous, solitary or scattered, buried in duff or soil. Ectomycorrhizal; most collections come from mid- to high elevation, mature and old growth fir (Abies spp.) forests (Siegel et al. 2019). Fruiting in summer and fall.
Prolonged droughts and decades of fire suppression have drastically altered western montane forests, leading to thicker, denser, Abies dominated forests. As a result, hotter, stand replacing fires (rather than patchwork and understory burns) are commonplace, altering appropriate habitat drastically, and making it ill-suited for this species.
A poorly known species; more sites need to be discovered to properly assess and identify suitable habitat.
Elliott, T.F. and Trappe J.M. 2018. A worldwide nomenclature revision of sequestrate Russula species. Fungal Systematics and Evolution 229-242. doi:10.3114/fuse.2018.01.10
Smith, A.H. 1963. New astrogastraceous fungi from the Pacific Northwest. Mycologia 55: 421–441.
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.
Trappe, J. M., T. Lebel & M.A. Castellano. 2002. Nomenclatural revisions in the sequestrate russuloid genera. Mycotaxon 81:195–214.