Described from a collection made in Idaho, USA (Smith & Zeller 1966).
Many Rhizopogon species lack distinctive morphological characters, and can only be reliably identified with genetic sequences.
The reported Channel Island, California collection was associated with Bishop Pine; and follow-up studies only found Rhizopogon vulgaris and R. occidentalis on the islands. We are not considering that collection as part of this assessment.
Rhizopogon flavofibrillosus is a hypogeous fungus with a pallid peridium with straw yellow to brownish yellow rhizomorphs, purplish red reaction to KOH on the peridium, a whitish to olivaceous gleba, and ellipsoid to nearly oblong spores (Siegel et al. 2019).
Currently known from 10 locations total; from the Siskiyou mountains in northern California and southwest Oregon, the Cascade Range in Oregon, a single site in Idaho and two in Montana. Little is known about habitat requirements.
Widespread, but rarely collected, and with a disjunct distribution. Known from the Klamath Range in California, north through the Siskiyou Mountains and Cascade Range in Oregon, east into the northern Rocky Mountains.
Population is widespread in disjunct, small populations in conifer forests; currently known from 10 locations in the Siskiyou mountains in California and Oregon, the Cascade Range in Oregon and Rocky Mountains in Idaho and Montana. This species is too poorly known to have its habitat preferences and trends assessed. Many Rhizopogon species have spores which stay viable in soil for many years; waiting for conditions to be optimal before growing. It is unknown if Rhizopogon flavofibrillosus is one of the ‘sporebank’ species.
Population Trend: Uncertain
Hypogeous, solitary or scattered, buried in duff or soil. Ectomycorrhizal, found in forest with Douglas-fir (Pseudotsuga menziesii), Ponderosa Pine (Pinus ponderosa), and other members of Pinaceae. This species is dependent on mycophagy (primarily eaten by small mammals) for spore dispersal.
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. Pine beetle outbreaks due to prolonged droughts and higher temperatures have killed millions of coniferous trees, in particular pines in the Rocky Mountains and the Sierra Nevada.
This species is included on the United States Forest Service Northwest Forest Plan Survey and Manage list of rare/old growth forests dependent fungi (Castellano et al. 1999).
Modern taxonomic work on Rhizopogon. Habitat associations of this species. Extent of populations.
Castellano, M., Smith, J.E., O’Dell, T., Cázares, E. and Nugent, S. 1999. Handbook to Strategy 1 Fungal Species in the Northwest Forest Plan. General Technical Report PNW-GTR-476. United States Department of Agriculture.
MyCoPortal. Mycology Collections Portal. Available at: http://mycoportal.org
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. and Zeller, S.M. 1966. A preliminary account of the North American species of Rhizopogon. Memoirs of the New York Botanical Garden. 14: 1–178