Described as Gymnomyces xerophilus from a collection made in Yuba County, California, USA (Smith et al. 2006)
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).
These hypogeous Russula (Gymnomyces) are notoriously hard to identify to species, requiring diligent microscopic examination, and occasionally, the genetic fingerprint. A key to oak associated “Gymnomyces” can be found in Smith et al. (2006).
Russula xerophila is a small to medium sized hypogeous fungus growing with oaks (Quercus spp.) in the northern Sierra Nevada Foothills. It is currently known from two locations, in a habitat under threat.
Currently known from two locations in California, USA, in the northern Sierra Nevada foothills ‘oak zone’. Although similar habitat exists on the on the western (drier) side of the valley, no surveys have been conducted in the oak zone of this area (Siegel et al. 2019).
A poorly known species, occurring in the Sierra Nevada foothills oak zone. Much of this habitat has been lost to urban development and farmland and is susceptible to elevated levels of N deposition from agriculture in the Central Valley, and oaks have suffered from drought stress.
Population Trend: Decreasing
Hypogeous, solitary or scattered, buried in duff or soil. Ectomycorrhizal, associated with Blue Oak (Quercus douglasii), Interior Live Oak (Q. wislizeni), and Black Oak (Q. kelloggii), possibly with other Quercus species. Fruiting in spring.
It is dependent on mycophagy (primarily eaten by small mammals) for spore dispersal.
Loss of habitat due to urban development and agriculture land.
Prolonged droughts have stressed and killed many oaks in the southern and central Sierra Nevada Foothills. Drought also suppresses fruitbody formation.
Drift from artificial (nitrogen) fertilizers in agriculture lands in the Central Valley changes the composition of ectomycorrhizal fungi on the roots, and can suppresses fruitbody formation. No studies have been done to see if Russula xerophila is affected.
Targeted surveys for this species, especially from the southern Sierra Nevada foothills, and on the west side of the Central Valley on the eastern slopes of the Coast Range.
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
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, M.E., Trappe, J.M., Rizzo, D.M. and Miller, S.L. 2006. Gymnomyces xerophilus sp. nov. (sequestrate Russulaceae), an ectomycorrhizal associate of Quercus in California. Mycological Research 110 (5): 575–582