Russula benwooii Bazzicalupo, D. Miller & Buyck.
Index Fungorum number: IF553815 Facesoffungi number: FoF 03648
Etymology: named for Benjamin Woo, whose collections were the basis of this study.
Holotype: BW931 (WTU, sub nr. F-038559)
Pileus firm and fleshy, (4–)8–11(–16) cm diameter, convex, then becoming gently depressed in the centre, but never deeply funnel–shaped, sometimes radially fissuring from the margin inwards, with mostly even margin or – in less fleshy specimens – also weakly striate; surface viscid when wet, matte to shiny when dry, variably peeling, extremely variable in colour and with the centre either paler or darker than the rest of the cap, mostly coming in tones of brown to brownish tan, mixed or not with shades of olive, reddish-pink, wine red or purple, but also sometimes with dominance of single colours, for example, entirely wine red, olive–green or intense purple. Lamellae adnate, normally spaced (ca 1 lamella per mm (L/mm)) or sometimes wider, pale cream to yellow (of Woo specimens, ~85% recorded as ‘cream’; ~15% as ‘yellow’), occasionally bifurcating near the cap margin, lamellulae of variable length often present. Stipe mostly distinctly widening toward the base, shorter than the cap diameter, white or partly to entirely tinged with purple or red, sometimes staining brown. Odor none. Taste mild, sometimes slightly spicy in gills (of Woo specimens, ~20% recorded as having hot gills). Spore print cream (of Woo specimens, ~60% Crawshay B–C, ~40% Crawshay D–E). Spores broadly ellipsoid, (6.9–)9.16–9.22–9.28(–12) × (5–)7.09–7.14–7.18(–8.6) µm, Q = (1–)1.28–1.29–1.3(–1.5), ornamentation subreticulate, composed of strongly amyloid, sometimes slightly curved, conical warts, (0.4–)1.1–1.12–1.14(–1.9) µm high, with some interconnections; suprahilar spot present as a strongly amyloid patch. Basidia (44–)51–56–61(–65) × (10.5–)11.5–12.5–13.5(–14.5) µm, 4-spored, clavate. Lamellar trama mainly composed of sphaerocytes, mixed with some cystidioid hyphae. Hymenial cystidia broadly clavate, obtuse–rounded at the top, 60–75(–85) µm long and 10–12 µm wide, similar near the gill edge, most often weakly SV+ (reaction in sulfovanillin: ~40% colouring grey, ~25% no reaction, others turning red, violet, and purple). Pileipellis not sharply delimited from the underlying context of filamentous hyphae and sphaerocytes; suprapellis composed of densely packed narrow hyphae, 2–4 µm wide, with terminal cylindrical cells with narrowing, sometimes capitate tips. Pileocystidial cells ~30–35 µm long and up to 7 µm in width, with obtuse tips and refringent contents. Acidoresistant incrustations absent. Clamp connections absent in all parts. FeSO4: none to tan.
Habitat and distribution: associated with Tsuga heterophylla (as evidenced by deposited ectomycorrhizal sequences for western hemlock), possibly also with Pseudotsuga menziesii as the trees frequently co-occur, and potentially also other conifers that were occasionally present: Picea stichensis, Pinus contorta, Abies, and Larix (Larch). Only known from the Pacific Northwest (USA: Oregon, Washington, Idaho; Canada: British Columbia).
Material examined: U.S.A., Oregon, Clackamas County, Wildcat Mountain, 04 Sep 1999, B. Woo BW805A, F-038724 (WTU), GenBank ITS2: KX813469; ibidem, Lincoln City, East Devils Lake Park, 123.997778˚W, 44.966667˚N, 8 m alt., 26 Oct 2001, B. Woo BW931, F-038559 (WTU, holotype), GenBank ITS2: KX813560; Washington State, Asahel Curtis Loop Trail, 121.474722˚W, 47.390833˚N, 650 m alt., 30 Sep 1999, B. Woo BW830, F-039368 (WTU), GenBank ITS2: KX813487; ibidem, Millersylvania State Park, 122.9083˚W, 46.91˚N, 67 m alt., 20 Oct 2004, B. Woo BW1005, F-038884 (WTU), GenBank ITS2: KX812908; ibidem, Sloan Creek Camp, 121.287778˚W, 48.0575˚N, 630 m alt., 19 Sep 1999, B. Woo BW816, F-039305, (WTU), GenBank ITS2: KX813478.
Notes: Russula benwooii corresponded to clade 9 in our phylogeny, to Woo sp. 67 in Bazzicalupo et al. (in press) and UNITE SH DOI: https://plutof.ut.ee/#/datacite/10.15156/BIO/SH299776.07FU. It appeared as a well-supported sister to European R. paludosa, but its phylogenetic position was otherwise unresolved.
This mild, firm and robust Russula could be easily confused with equally variable species in subsections Xerampelinae (particularly R. xerampelina) and Integrinae (particularly R. integra), all species that are known as strict conifer associates. Woo’s database records showed that R. benwooii had indeed been confused in the past with R. xerampelina (particularly when specimens had a browning or tinted stipe). Russula benwooii could usually be distinguished from R. xerampelina by its absence of a green FeSO4 reaction and lack of a fishy smell. R. benwoii has been confused with R. vinosa (known as ‘R. occidentalis’ in the Pacific Northwest), the two are phylogenetically distinct. We concluded that R. maxima Burl., another taxon described from the Pacific Northwest was not synonymous with our species. The type of R. maxima was never sequenced but a comparison of morphological descriptions showed that spores of the two species were different and the spore ornamentation was much shorter, below 0.5 (–1) µm high in Burlingham’s species (Buyck et al. 2015; Hesler 1961).
The closest species in the phylogeny and in the UNITE database was R. paludosa (SH299756.07FU), with a 95% match. Samples with identical ITS sequences have only been reported from the Pacific Northwest to date [Canada: Campbell River, BC (KP403057, EU597055, DQ367916), BC (FJ152488, JF899571, KP889681)].