Strobilomyces calidus

Strobilomyces calidus L.H. Han, J. Xu & Zhu L. Yang.

Index Fungorum number: IF 824855; MycoBank number: MB 824855

Basidiomes medium-sized. Pileus 60–90 mm diam, subhemispherical, dry, densely covered with black (9F7), more or less erect conical to pyramidal scales, small, 1–3 mm high, 1–3 mm diam at base, subpellis context dirty white (1B1) to brown-black (9E4); margin occasionally appendiculate with a few slender ciliate veil remnants concolorous with pileal surface; context white (8A1), quickly changing to orange-red (6B8) then black (10E1) on exposure. Tubes adnate with decurrent tooth, white (6A1) then smoky grey (8C1); hymenophoral pores angular, large, 1–2 mm diam; pores and tubes concolorous, white (14A1) then cinnamon grey (5D1), immediately staining brown-black (6E6), then black (17F8) on exposure. Stipe 65–110 mm long, 6–15 mm diam, subcylindrical or slightly thickening to base; surface with elongate reticulum at upper, entirely with black granular scales; context white (8A1), discolouration similar to that of pileus; annulus and annular zone absent; basal mycelium grey-white (6B1).

Basidiospores [60/3/2] (7.5–)8.5–10 × 7–8(–9) μm (Q = 1.18–1.25(–1.28), Qm = 1.21 ± 0.04) excluding ornamentation, broad ellipsoid, dark brown (7D5), echinate with confluent tubercles and irregular incomplete reticulation, ornamentation 0.5–1 μm high; apiculus 0.5 μm long. Basidia 32–44 × 11–17 μm, narrowly clavate to clavate, 4-spored; sterigmata 4–6 μm long. Hymenophoral trama boletoid; hyphae cylindrical, 6–10 μm wide. Cheilocystidia 35–65 × 15–25 μm, abundant, narrowly lageniform to narrowly conical, hyaline or with dark brown (5C8) plasmatic pigment, thin-walled. Pleurocystidia 45–65 × 15–18 μm, numerous, narrowly lageniform to narrowly utriform, thin-walled. Pileipellis an intricate trichodermium, wrapped in bundles, composed of 4–18 μm wide subradially arranged hyphae, with short attenuated terminal cells, cell wall dark brown (5E8) and slightly thickened (< 1 μm). Pileal trama composed of 4–11 μm wide interwoven hyphae. Hyphae of scales on stipe similar to those on pileus. Stipe trama composed of 3–13 μm wide cylindrical hyphae. Clamp connections absent.

Habitat & Distribution: Solitary or scattered on soil in forests dominated by Fagaceae; presently recorded from tropical China.

Additional specimen examined: CHINA, Yunnan Province, Puer City, Taiyanghe National Forest Park, 1326 m elev., 2 Aug. 2014, X.B. Liu 438 (HKAS 87084).

Notes: Strobilomyces calidus is characterized by its medium-sized basidiomes (60–90 mm diam), pileus with black, small, more or less erect conical to pyramidal scales (1–3 mm diam), stipe entirely granulated with black scales, large hymenophoral pores (1–2 mm diam), small to medium-sized echinate basidiospores (8.5–10 × 7–8 μm) with confluent tubercles and irregular incomplete reticulum and orange-red discolouration of the context on exposure. The taxon is recorded from tropical China only. Phylogenetically, S. calidus is closely related to S. densisquamosus, a species described in the present paper. Morphologically, S. calidus resembles S. anthracinus because of their black scales on the pileus and stipe. However, S. anthracinus has a charcoal black to black basidiome, a stipe with fluffy floss, smaller hymenophoral pores 0.5–1 mm diam, reticulate basidiospores, rusty red discolouration of the context on exposure and subtropical distribution.

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.

Fig. 2 Representative basidiomes of Strobilomyces species with non-reticulate basidiospores. — a1–a2. S. calidus (HKAS 84700); b1–b2. S. densisquamosus (HKAS 83112, holotype); c1. S. echinatus (NEST 1597); c2. S. echinatus (NEST 1818); d1. S. giganteus (HKAS 59637); d2. S. giganteus (HKAS 74967); e1–e3. S. seminudus (HKAS 80459); f1–f2. S. subnudus (HKAS 83823); g1–g2. S. velutinus (HKAS 84776); h1–h2. S. cf. velutipes (NY 2072516). — Scale

bars = 20 mm.