Entoloma reductum Xiao L. He & E. Horak
MycoBank number: 817513
Pileus 8–25 mm broad, conchate, broadly convex to applanate, greyish at first, becoming greyish-brown with age, entirely matted-tomentose or matted-fibrillose, fibrils greyish-white, slightly hygrophanous, margin weakly transparent-striate. Lamellae moderately close, with two tiers of lamellulae, adnate, ventricose, up to 4 mm wide, whitish or pale greyish at first, becoming pink or rust pinkish with age, entire edges concolorous. Stipe 1–2.5 × 0.5–1 mm, lateral, strongly reduced, pale grey brownish, covered with minute pale greyish fibrils, base with white mycelium. Rhizoids absent. Context thin, greyish, unchanging on exposure. Odour absent. Taste not distinctive. Basidiospores 8–10.5 (12) × 6–7.5 µm (x = 8.8 ± 0.2 × 6.6 ± 0.3 µm), Q = 1.25–1.61, Q = 1.35 ± 0.05, 5–6-angled, heterodiametric in profile view. Basidia 20–34 × 8–11 µm, clavate, 4-spored, clampless. Lamellar edge fertile. Cheilocystidia, pleurocystidia and caulocystidia absent. Pileipellis a cutis composed of cylindric hyphae, terminal cells (25–) 40–65 × 5–7 µm, repent or slightly uplifted, cylindrical or slender clavate, non-gelatinised wall thin, smooth or minutely encrusted with slightly pale brown pigment. Oleiferous hyphae present in pileipellis. Clamp connections present in the pileipellis.
Habitat: On decayed stump of Castanopsis sp.; on soil or rock amongst moss in forest dominated by Quercus sp.
Additional materials examined: China. Sichuan Prov.: Yajiang County, Gexigou National Nature Reserve, ca. 2800 m elev., 30°03'N, 101°E, on rock amongst moss, 6 August 2015, X.L. He (SAAS 1016); on soil amongst moss, 3 August 2014, X.L. He (SAAS 1897); on rock amongst moss, 3 August 2014, X.L. He (SAAS 2068). Yunnan Prov.: Binchuan County, Jizu Mountain, ca. 2600 m elev., 25°58'N, 100°21'E, on decayed stump of Castanopsis sp., 8 September 2015, X.L. He (SAAS 1608; ZT 13606).
Notes: Entoloma reductum is unique by the combined features of pleurotoid, greyish-brown basidiomes, presence of brownish encrusting and intracellular pigment and presence of scattered clamp connections. Entoloma reductum can be confused with E. byssisedum (Pers.) Donk; however, the latter species is separated by the larger basidiospores (9.5–12 × 6.5–8.0 µm). E. byssisedum var. microsporum is separated by the more reniform and paler coloured pileus and, in addition, the two species are well distinguished by their ITS and RPB2 sequences. Claudopus dulcisaporus Largent, described from North America, shares with E. reductum the brown basidiomes and the size of the basidiospores, but it can be distinguished not only by the presence of abundant cheilocystidia, but also the habitat. Claudopus graveolens Largent is distinguished by smooth and bicolorous pileus, presence of cheilocystidia; finally, C. avellaneus differs by the narrower basidiospores (8–10 × 5–6 µm).
Fig. 1 Phylogenetic reconstruction of Claudopus based on ITS sequences. Maximum parsimony bootstrap values (BS > 50%) are indicated above or below the branches, new species are in bold.