Russula rhodocephala Bazzicalupo, D. Miller & Buyck.
Index Fungorum number: IF553822 Facesoffungi number: FoF 03655
Etymology: refers to the red colour of the cap.
Holotype: BW337 (WTU, sub nr. F-039507)
Pileus 2–12 cm diameter, very fleshy and firm, convex to shallowly depressed or irregularly wavy with downward margin without striations; surface bright scarlet, deep crimson red to brownish reddish orange. Lamellae adnate to slightly decurrent, spacing normal (ca 1 L/mm) to slightly wider, mostly equal although lamellulae can be common and bifurcations occasionally present, cream coloured. Stipe shorter than the cap diameter in mature fruiting bodies, robust and cylindrical, flushed with pink or red. Context white, unchanging with age or on injury, the lower stipe may bruise yellow, turning pink with FeSO4. Odor none or weakly pleasant. Taste very hot in gills and flesh, (of Woo specimens, 100% recorded as ‘hot’ in both gills and flesh, 50% of flesh recorded as some degree of ‘acrid’). Spore print yellowish, (~40% of Woo specimens recorded as Crawshay B–C, ~60% D–E). Spores broadly ellipsoid, (6.2–)7.83–7.87–7.92(–10) × (4.8–)6.28–6.32–6.35(–7.5) µm, Q = (1–)1.24–1.25–1.26(–1.5), ornamented with mostly isolated, amyloid, conical warts, (0.2–)0.68–0.69–0.71(–1.4) µm high, with rare connections; suprahilar spot a strongly amyloid patch. Basidia (36.5–)41–45–49(–55) × (9–)10–11–12(–14) µm, 4-spored. Lamellar trama mainly composed of sphaerocytes, intermixed with cystidioid hyphae. Hymenial cystidia 60–65(–70) × 7–8 µm, broadly clavate, obtuse-rounded at the tip, SV+ and dark purple in sulfovanillin. Pileipellis not sharply delimited from the underlying context of filamentous hyphae and sphaerocytes; suprapellis composed of loosely arranged, branching hyphal terminations, with cylindrical terminal cells. Pileocystidia sometimes so long that it was hard to determine their length, when measurable up to ~40 µm long and up to 8 µm in width and with obtuse tips; contents refringent, also abundantly continuing as cystidioid hyphae with refractory contents in subpellis and trama. Acidoresistant incrustations absent. Clamp connections absent in all parts.
Habitat and distribution: Pinus contorta. Known from USA: California, Idaho, Oregon, Washington; Canada: British Columbia.
Examined material: U.S.A., Idaho, Priest Lake, 116.916667˚W, 48.565556˚N, 765-900 m alt., 29 Sep 1978, B. Woo BW201, F-038413 (WTU), GenBank ITS2: KX813043; ibidem, Priest Lake, North Lake Road, 116.816667˚W, 48.748889˚N, 770 m alt., 24 Sep 1983, B. Woo BW361, F-038604 (WTU), GenBank ITS2: KX813143; Oregon, Lincoln City, East Devils Lake Park, 124.01194˚W, 44.97˚N, 6 m alt., 15 Nov 1986, B. Woo BW438, F-038632 (WTU), GenBank ITS2: KX813199; ibidem, 123.997778˚W, 44.97˚N, 6 m alt., 15 Nov 1999, B. Woo BW860, F-039103 (WTU), GenBank ITS2: KX813506; ibidem, Astoria, Fort Stevens, 123.96861˚W, 46.185278˚N, 15 m alt., 11 Nov 1989, B. Woo BW486, F-038655 (WTU), GenBank ITS2: KX813231; Washington, Fort Canby State Park, 124.063889˚W, 46.285833˚N, 6 m alt., 12 Nov 1988, B. Woo BW463, F-038363 (WTU), GenBank ITS2: KX813218; ibidem, Shelton power line, 123.066667˚W, 47.250833˚N, 60 m alt., 24 Oct 1982, B. Woo BW337, F-039507 (WTU, holotype), GenBank ITS2: KX813126.
Notes: Russula rhodocephala corresponds to Clade 4 in our phylogeny, to Woo sp. 35 in Bazzicalupo et al. (in press) and to UNITE SH DOI https://plutof.ut.ee/#/datacite/10.15156%2FBIO%2FSH218433.07FU (100% match ITS2).
Until now, R. rhodocephala has been referred to as R. sanguinea Fr. Both R. rhodocephala and R. sanguinea are associated with Pinus (Bills and Miller Jr 1984). Even though the European R. sanguinea appeared as the sister to our species with significant support, it differed from our species by more than 3% in the ITS2 region. PlutoF maps showed that their distributions differed. The only records of sequences matching R. rhodocephala at 99.5% identity cutoff were from the American west: [Canada: Rocky Point, Victoria, BC (UDB031015), U.S.A.: California (GU180315), corresponding to UNITE SH DOI: https://plutof.ut.ee/#/datacite/10.15156/BIO/SH297359.07FU. Relaxing the identity cutoff to 99%, samples with a wider geographical distribution across the United States and Mexico were included: https://plutof.ut.ee/#/datacite/10.15156/BIO/SH130463.07FU. Further relaxing the cutoff to 97% cutoff included sequences found from Korea, China and Japan (March 2017): https://plutof.ut.ee/#/datacite/10.15156%2FBIO%2FSH030433.07FU. Reflecting their sequence differences, European Russula sanguinea corresponded to UNITE SH218425 represented by sample R. sanguinea UDB011161, while N. American R. rhodocephala (accessioned into GenBank as “R. sanguinea“) corresponded to UNITE SH218433.
The spore print colour described should be verified due to the surprisingly wide range recorded by Woo. However, a similar wide variation in spore print colour is given on Mushroomexpert.com for the eastern U.S. taxon identified as R. sanguinea (“creamy to yellowish or orange-yellow” (Kuo 2009).
The species could be confused with R. americana Singer, which appears a somewhat less robust taxon associating with Tsuga and perhaps also Abies, and has larger spores, 8.5–11.5 × 7–l0.8 (Singer 1939). R. americana also matches the description of R. rosacea var. macropseudocystidiata Grund. Detailed descriptions can be found in Roberts (2007) who distinguished R. americana from R. rhodocephala (under the name ‘R. sanguinaria’) by its taller and more slender habit and by its association with western hemlock (and possibly Abies) rather than pines. Unlike R. americana, R. rhodocephala is generally found in wet areas, often shows yellow staining on the lower stipe, and it has a more evenly coloured and shiny cap with the epicutis an ixotrichodermis. Most other red-capped, acrid species in the area produce whitish gills and spore prints, while the otherwise very similar R. californiensis Burl. grows with pine and oak in California, has a pale yellowish spore print, a more distinctly greying stipe, and especially, a distinctly more reticulate spore ornamentation (Burlingham 1936).