Strobilomyces albidus L.H. Han, J. Xu & Zhu L. Yang.
Basidiomes small to medium-sized. Pileus 50–70 mm diam, hemispherical or applanate, dry, covered with black-brown (5D8) to dark chocolate (6E7), patch-like to appressed scales or floss, 2–4 mm high, 3–5 mm diam at base, ground whitish (2A1); margin more or less appendiculate with triangular veil remnants concolorous with pileal ground; context white (8A1), staining rusty red (9C4) then black (10E1) on exposure. Tubes emarginate with decurrent tooth, white (6A1) then smoky grey (8C1); hymenophoral pores angular, small, 0.5–1 mm diam; pores and tubes concolorous, whitish (14A1) then smoky grey (4D1), immediately staining rudty red (6D8) then black (17F8) on exposure. Stipe 50–112 mm long, 4–13 mm diam, subcylindrical, curved; surface reticulated by extended tubes at top, entirely covered with whitish (1B2) thin fluffy floss; context white (8A1), discolouration similar to that of tubes; annulus or annular zone absent; basal mycelium dirty white (1B1) to grey-white (6B1).
Basidiospores [180/9/5] (6.5–)7–9 × 6–7(–8) μm (Q = 1.1–1.29(–1.38), Qm = 1.18 ± 0.04) excluding ornamentation, subglobose to broad ellipsoid, dark brown (7D5), completely reticulate with meshes 2–3 μm diam and 1–2 μm high; apiculus 0.5 μm long. Basidia 37–45 × 13–17 μm, narrowly clavate to clavate, 4-spored; sterigmata 3–6 μm long. Hymenophoral trama boletoid; hyphae cylindrical, 7–10 μm diam. Cheilocystidia 48–76 × 15–20 μm, subfusiform to conical or sublageniform, hyaline or with yellow brown (5B7) plasmatic pigment, thin-walled. Pleurocystidia 44–63 × 9–14 μm, numerous, narrowly lageniform to subfusiform with long beak, thin-walled. Pileipellis an intricate trichodermium, composed of 6–16 μm wide cylindric to submoniliform hyphae; hyphae roughly intertwined into clusters, with short obtuse terminal cells; cell wall dark brown (5E8), slightly thickened (< 1 μm). Pileal trama composed of 5–10 μm wide interwoven hyphae. Hyphae of scales on stipe similar to those on pileus. Stipe trama composed of 3–12 μm wide cylindrical hyphae. Clamp connections absent.
Habitat & Distribution: Solitary or scattered on soil in forests dominated by Lithocarpus spp. and Castanopsis spp.; currently recorded from tropical China and Thailand.
Additional specimens examined: CHINA, Yunnan Province, Jinghong City, Dadugang town, 1300 m elev., 22 July 2007, Y.C. Li 934 (HKAS 52621); same location, 10 July 2014, L.H. Han 426 (HKAS 84722); Baoshan City, Tengchong County, longteng secondary road X193-52, 1650 m elev., 4 Aug. 2013, G. Wu 610 (HKAS 74924); Xishuangbanna City, Mengla County, Xishuangbanna Nature Reserve, 1300 m elev., 8 July 2014, L.H. Han 399 (HKAS 84695); Taiwan Province, Nantoh, H. Sato (MAK s305). – Thailand, Chiang Mai Province, Highway 1095, 1150 m elev., 10 June 2006, R.E. Halling et al. 8800 (NY1393538).
Notes: Strobilomyces albidus is characterized by its small to medium-sized basidiomes (50–70 mm diam), pileus with black-brown to dark chocolate, medium-sized, patch-like to appressed scales or floss (2–4 mm high, 3–5 mm diam at base), stipe entirely with whitish thin fluffy floss, small hymenophoral pores (0.5–1 mm diam), small subglobose to broad ellipsoid basidiospores (7–9 × 6–7 μm) with large meshes (2–3 μm diam × 1–2 μm in height), rusty red discolouration of the context on exposure (Fig. 3a1–a2, 4a) and tropical distribution in Asia. This species occupies a relatively isolated position in the phylogenetic tree (Fig. 1). It resembles S. echinocephalus by its pileus with black-brown patch-like to appressed scales or floss. However, S. echinocephalus has slightly larger basidiospores (8.5–10 × 6.5–8 μm), stipe entirely covered with black-brown to black thick floss, and context changing directly to grey-black on exposure (Gelardi et al. 2013; Fig. 3h1–h2, 4h). Furthermore, the known distribution range of S. echinocephalus is restricted to subtropical regions of East Asia (Gelardi et al. 2013, Han et al. 2018, this study).
Fig. 1 Phylogeny inferred from four-locus dataset (RPB1- RPB2-TEF1-COX3), with branch lengths based on the Maximum Likelihood analysis. Only MLB over 70 % and BPP over 0.95 are given in the tree. Bold black and red branches represented independent evolutionary lineages that were well supported by at least one locus and not contradicted by any other locus. Bold red branches showed phylogenetic species. Eight newly described species are indicated in black bold letters. The Roman numerals (I, II, III and IV) indicated the four major clades of Strobilomyces. The two sections are displayed on the right of the phylogram.