Inocybe pileosulcata E. Horak, Matheny & Desjardin, 2015

Horak, Egon, Matheny, P. Brandon, Desjardin, Dennis E. & Soytong, K., 2015, The genus Inocybe (Inocybaceae, Agaricales, Basidiomycota) in Thailand and Malaysia, Phytotaxa 230 (3), pp. 201-238 : 227-229

17. Inocybe pileosulcata E. Horak, Matheny & Desjardin , spec. nov. Fig. 16a–g ; Pl. 5b

MycoBank MB 519919

Etymology: pileus (Lat.), pileus; sulcatus (Lat.) sulcate, split.

Diagnosis: Basidiomes medium- to large-sized. Pileus 35–55 mm wide, conspicuously sulcate and splitting(plicate) from the margin to the smooth umbo, veil remnants absent, brownish orange to light yellowish brown, elsewhere more or less greyish white to yellowish grey. Stipe 40–55 × 3–4 mm, with a conspicuous marginate basal bulb up to 10 mm wide, lacking appendiculate veil remnants, surface entirely pruinose, white or pale orange. Basidiospores 10–12 × 8.5–10 μm, stellate. Cheilocystidia, pleurocystidia, and caulocystidia 55–70 × 18–26 μm, fusoid or utriform, with hyaline walls up to 5 μm thick. In tropical lowland and montane forests dominated by Dipterocarpus , Castanopsis , Shorea , intermixed with Pinus kesiya , Thailand and Malaysia.

Holotype:— THAILAND. Chiang Mai Prov.: Hwy 1095, at 22 km marker, N19˚07.570‘, E98˚45 ‘647‘‘, 750 m elev., on soil in tropical submontane forest (dominated by Dipterocarpus ), 750 m elev., 11 Jun. 2006, leg. A. Neves & D. E. Desjardin ( DED8058 , holotype, SFSU; ZT13025 , isotype) GenBank accession no. EU600838.

Misappl.: Inocybe asterospora Quél. sensu Horak , Persoonia 10: 202, 1979. — Inocybe asterospora Quél. sensu Turnbull, Edinb. J. Bot. 52: 353, 1995.

Pileus (30–) 35–55 mm wide, at first convex becoming broadly plano-convex with low but distinct umbo, conspicuously sulcate and splitting (plicate) from margin to glabrous umbo, radially appressed-fibrillose on ridges of plicae; surface dry, veil remnants absent; umbo and plicae pale brownish orange (5C3) to light yellowish brown (5D4), elsewhere pale dingy greyish white to yellowish grey (4B2); context in pileus up to 1 mm thick, white, unchanging upon exposure. Lamellae 32–44 reaching stipe, 3–7 lamellulae, close, adnexed, up to 5 mm wide, pale brownish orange (5C3) becoming greyish brown (6D3), entire or subfimbriate edges concolorous. Stipe 40–55 × 3–4 mm, central, cylindrical, equal until a distinctive marginate bulb up to 10 mm wide at base, margin of bulb devoid of appendiculate volva-like veil remnants, pruinose all over, white or pale orange (5A2), dry, hollow; cortina absent. Odor and taste not distinctive.

Basidiospores 10–12 × 8.5–10 μm, ovoid, conspicuously nodulose (stellate), covered with rather large, conspicuous, obtuse-conical nodules, yellow-brown, brown (7E–F6) in deposit. Basidia 30–34 x 10–13 μm, 4-spored, clavate. Cheilocystidia 55–70 × 18–26 μm, fusoid or utriform, metuloid, walls up to 5 μm thick at apex, hyaline, crystals present; paracystidia 15–25 × 10–15 μm, vesiculose or subglobose, walls thin and hyaline. Pleurocystidia similar to cheilocystidia. Caulocystidia similar to cheilocystidia, intermixed with clavate, thin-walled, hyaline cells. Pileipellis a cutis of repent, cylindrical hyphae, 2–4 μm wide, terminal cells not differentiated, non-gelatinized wall, thin, hyaline; subpellis hyphae cylindrical or broadly ovoid, 8–14 μm wide, encrusted with yellow-brown pigment; oleiferous hyphae absent. Clamp connections present.

Habitat On soil in tropical lowland and montane forest (750–1700 m elev.) dominated by Dipterocarpus , Castanopsis , Shorea , intermixed with Pinus kesiya .

Known distribution: Malaysia (Selangor, Pahang, Sabah), Northwest Thailand (type).

Other specimens examined: MALAYSIA. Selangor: Kepong, Forest Research Institute (FRIM), on soil in tropical lowland forest (under Shorea sumatrana ), 19 Mar. 1993, leg. E. Turnbull 27 (E). Pahang: Tembeling, 8 Nov. 1930, leg. E.J.H. Corner (ZT 78-066). Sabah: Mt Kinabalu, Mesilau River, on soil in tropical montane forest, 1700 m elev., 19 Jan. 1964, leg. E.J.H. Corner RSNB 5015 (E, ZT 78-067); same locality and habitat, 21 Apr. 1964, leg. E.J.H. Corner RSNB 8387 (E; ZT 78-065). THAILAND. Chiang Mai Prov.: same locality as the type, on soil in tropical submontane forest (dominated by Dipterocarpus , Castanopsis , with scattered Pinus kesiya ), 30 Jun. 2007, leg. D.E. Desjardin (DED8164, SFSU) GenBank accession no. GQ892996, GQ892951.

Notes: Based on present collections, I. pileosulcata is reported from tropical lowland and montane forests both in Thailand and Malaysia. The medium-sized to large-sized basidiomes of this spectacular species are characterized by the deeply and radially sulcate-splitting pileus, the pruinose stipe with distinctly marginate basal bulb, the large, thick-walled cheilocystidia and pleurocystidia and the large basidiospores with distinctive conical projections. All macroscopic and microscopic characters are similar to the European I. asterospora Quél. ( Stangl 1989, Horak 2005), and thus it is not surprising that earlier records of this taxon were erroneously filed under this name ( Horak 1979, Turnbull 1995).

LSU sequences of this species form two distinct sister lineages apart from a North American I. aff. asterospora . Together with Inocybe sp. DED8044, also from Thailand but for which morphological data are insufficent, these sequences form a robust asterospora -like clade.

Figures

PLATE 5. a. Inocybe fragilissima (DED8061, holotype). b. Inocybe pileosulcata (DED8058). c. Inocybe parvibulbosa (ZT10099, holotype). d. Inocybe parvibulbosa (DED8021). Scale bars = 10 mm. Photos a, b, d, by Dennis Desjardin, c, by Egon Horak.

FIGURE 16. Macroscopic and anatomical features for Inocybe pileosulcata (DED8058, holotype). a. Basidiomes. b. Basidiospores. c. Basidium. d. Cheilocystidia. e. Paracystidia. f. Caulocystidia. g. Pileipellis. Scale bars: basidiomes = 20 mm, basidiospores = 10 μm, basidia and cystidia = 20 μm, pileipellis = 40 μm. Drawings by Egon Horak.