Clitopilus brunneiceps S.P. Jian & Zhu L. Yang, sp.
Basidiomata clitocyboid, medium-sized. Pileus 30–45 mm wide, plano-convex to slightly concave
or concave; surface brownish gray (3D1) at center, gray (3C1–B1) on the edge or uniformly gray (4B1),
usually smooth, but sometimes squamose; margin incurved, usually even; context 3–5 mm thick, whitish (2A1) to chalk white (1A1). Lamellae decurrent, yellowish white (1A2) to slightly yellowish pink (6A2–3), somewhat crowded, edges entire and concolorous, lamellulae numerous. Stipe 20–30 × 5–6 mm, eccentric, equal; surface yellowish white (2A1–2) to grayish-white (1B2), fibrillose or obscurely striate; the base often with white (1A1) mycelium. Odor unrecorded.
Basidiospores 8–12(–13) × 5–7(–8) μm, Lm × Wm =9.65 (± 0.9) × 6 (± 0.5) μm, Q = (1.11–)1.13–2.03(–2.07) (Qavg = 1.63 ± 0.21) [91/4/4], hyaline, subfusiform to broadly fusiform, sometimes subovoid to ellipsoid in profile and face view, strongly angled in polar view with 5–6 obvious longitudinal ridges. Basidia 22–36 × 8–15 μm, clavate, hyaline, 4-spored, rarely 1- and 2-spored; sterigmata 2.5–5 μm. Lamellar trama more or less regular, composed of 4–10 μm wide, hyaline hyphae; oleiferous hyphae rare; subhymenium consisting of filamentous hyphal segments. Lamellae edges fertile. Pleurocystidia and cheilocystidia absent. Pileipellis a cutis composed of usually dry or slightly gelatinized, more or less radially arranged, repent or slightly interwoven, slightly loose, thin-walled, incrusted or smooth, cylindrical hyphae, 3–6 μm wide, with yellowish to yellow intracellular or parietal pigment; the subpellis made up of compactly arranged, yellow, smooth or incrusted, intracellular- or parietal-pigmented, cylindrical hyphae, 3–8 μmwide; pileal trama composed of hyaline, filamentous or oblong hyphae, 5–22 μmwide. Stipitipellis a cutis composed of compactly arranged, thin-walled, hyaline hyphae, 3–7 μm wide. Caulocystidia absent. Clamp connections absent.
Ecology and distribution: Single or scattered on soil in coniferous (viz., Pinus) or broad-leaved Fagaceae
forest, widely distributed in southwest, central, and northeast China, Jul to Aug.
Type specimens examined: CHINA. YUNNAN PROVINCE: Nanjian Yi Autonomous County, Caizi Mountain, scattered on soil in Pinus yunnanensis forest, alt. 2347 m, 15 Aug 2018, Y.J. Hou 95 (holotype KUN-HKAS104510). GenBank: ITS = MN061295; 28S = MN065684; rpb2 = MN148123; tef1 = MN166234; atp6 = MN133737.
Notes: In sect. Clitopilus, C. brunneiceps is also similar to C. griseobrunneus T.J. Baroni & Halling, C. paxilloides Noordel., and C. ravus W.Q. Deng & T.H. Li. Clitopilus griseobrunneus is reported from Costa Rica and distinguished from C. brunneiceps by the larger pileus (30–70 mm), larger basidiospores, and the presence of caulocystidia (Baroni and Halling 2000). Clitopilus paxilloides, originally described from Norway, has a graybrown pileus with darker spots on the surface and a tapered stipe (Noordeloos 1993). Clitopilus ravus is similar to C. brunneiceps, but the former has larger basidiospores with only 4–5 distinct longitudinal ridges (Deng et al. 2013b). Shape and Q values of basidiospores are quite variable for this species, which occupies a wide distribution in China.
Fig 1. Phylogenetic relationships among representative specimens of Clitopilus, Clitocella, and Clitopilopsis inferred from a multigene (28S, rpb2, tef1, and atp6) data set using both ML and BI methods (only the ML tree is shown). Bootstrap frequencies (>50%) and posterior probabilities (PP > 0.90) are shown on the supported branches. Sequences from type collections are marked, and altitude information of most specimens from KUN-HKAS is shown in the phylogram. New taxa are highlighted in red.