Inocybe hydrocybiformis (Corner & E. Horak) Garrido (1988: 17)

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 : 213-214

7. Inocybe hydrocybiformis (Corner & E. Horak) Garrido (1988: 17) Fig. 8a–g ; Pl. 8a

Basionym: Astrosporina hydrocybiformis Corner & E. Horak in Horak (1979: 170).

Pileus 10–20 mm wide, at first obtuse-conical becoming convex or expanded with more or less distinctive umbonate or acute papilla (habit is reminiscent of Cortinarius subgen. Hydrocybe-Telamonia), center smooth but scurfy, minutely squamulose or covered with small recurved conical scales, innate-fibrillose towards often rimose or sulcate, non-striate margin, deep umber brown or fuscous, dry, veil remnants at margin absent, velipellis absent; context concolorous, unchanging upon exposure; 5% KOH negative on pileus surface. Lamellae (18–) 24–32 reaching stipe, 3 (–7) lamellulae, adnexed to adnate, ventricose, up to 2 mm wide; at first fuscous cinnamon, very dark umber brown with rusty tinge in age; fimbriate edges white. Stipe 25–35 (–40) × 1–1.5 mm, cylindrical, equal, base rarely swollen (up to 3.5 mm diam), concolorous with pileus all over, fibrillose (but not pruinose) at apex, smooth towards base, dry; cortina not observed; context solid. Odor and taste not distinctive.

Basidiospores 8–10 × 7.5–8.5 μm, ovoid, slender conical or cylindrical, occasionally also with saddle-shaped projections up to 2.5 μm long, brown, brown in deposit. Basidia 25–36 × 7–8 μm, 4-spored, clavate. Cheilocystidia 40–70 × (8–) 10–20 μm, polymorphic, mostly cylindrical or clavate-capitate, often with blunt, forked or irregular fingerlike projections at apex, in 5% KOH filled with conspicuous, strongly refringent, granular, yellow or orange content, thin-walled, crystals absent; paracystidia absent. Pleurocystidia absent or scattered (size and shape like cheilocystidia). Caulocystidia shape and size like cheilocystidia. Pileipellis a cutis (or trichoderm) of cylindrical hyphae, 3–5 μm wide, terminal cells not differentiated, non-gelatinized thin wall, coarsely encrusted with dark brown pigment, often also brown plasmatical pigment present; subcutis hyphae cylindrical or slender ovoid, 8–16 μm wide, encrusted with pigment; oleiferous hyphae absent. Clamp connections present.

Habitat: Singly on lateritic soil (in recently burned) tropical lowland forest (dominated by Dipterocarpus obtusifolia , mixed with Tectona grandis or Pinus kesiya ) and in tropical submontane forest (dominated by Castanopsis , with scattered Pinus kesiya ), 425–1050 m elev.

Known distribution: Thailand, Malaysia, Singapore (type).

Specimens examined: SINGAPORE. Singapore: Singapore Botanical Garden, Gardens Jungle, 5 Sep. 1940, leg. E.J.H. Corner (E, holotype of I. hydrocybiformis ; ZT78-47, isotype). THAILAND. Mae Hong Son Prov.: S of Mae Hong Son, Hwy. 108, 235 km marker, road to TV Station 3–9, ca. 580 m elev., on lateritic soil (in recently burned) tropical submontane forest ( Dipterocarpus obtusifolia , Pinus kesiya ), 29 Jun. 2002, leg. E. & A. Horak (ZT10077) GenBank accession no. GQ892971; south of Mae Hong Son, Hwy. 108, 247 km marker, ca. 425 m elev., on lateritic soil in (recently burned) tropical lowland forest (dominated by Dipterocarpus obtusifolia , mixed with Tectona grandis ), 1 Jul. 2002, leg. E. & A. Horak (ZT9879) GenBank accession no. GQ892972. Chiang Mai Prov.: Hwy 1095 near 27 km marker, Pathummikaram Temple area near Ban Pha Deng, N19˚06‘28.8‘‘, E98˚44‘47.3‘‘, 1050 m elev., on soil in tropical montane forest (dominated by Dipterocarpus ), 27 Jun. 2007, leg. D.E. Desjardin (DED8144, SFSU); Hwy 1095, 22 km marker, N19˚07‘570 ‚‘, E98˚45‘647‘‘, 750 m elev., on soil in tropical montane forest (dominated by Dipterocarpus , Castanopsis , mixed with Pinus kesiya ), 30 Jun. 2007, leg. D.E. Desjardin (DED8165, SFSU) GenBank accession no. GQ892973. MALAYSIA. Negri Sembilan: Pasoh, FRIM Field station, on soil in tropical lowland forest (dominated by Shorea ), 2 Mar. 1992, leg. R. Watling 25436 (E, holotype of Inocybe aurantiocystidiata ). SINGAPORE. Singapore: Singapore Botanical Garden, Gardens Jungle, 4 Sep. 1937, leg. E.J.H. Corner (E, holotype of Astrosporina alienospora ; ZT78-50, isotype).

Notes: Inocybe hydrocybiformis is readily recognized both by macroscopic and microscopic characters. The pileus of the rather fragile and small basidiomes measures less then 20 mm wide, and the acute, conical (rarely umbonate) papilla is a significant feature to recognize this taxon that is probably widely distributed in southeast Asian tropical lowland and montane forests. In addition, I. hydrocybiformis is well distinguished by the peculiar cheilocystidia (and pleurocystidia) rarely encountered in Inocybe : the thin-walled, cylindrical or clavate-capitate cystidia are filled with a conspicuous, yellow, strongly refringent content. Crystals at the apex of the cystidia are absent. Note that Horak (1979) reported pleurocystidia as absent from material collected in Singapore and Malayasia but present though scattered in Thai material.

Two other Inocybe species with yellow colored cheilocystidia and similar basidiospores as observed in I. hydrocybiformis occur in the general region. The first taxon is the Malayan I. aurantiocystidiata Turnbull & Watling (1995) , which differs from I. hydrocybiformis by the marginate stipe base and violaceous context. The second species reminiscent of I. hydrocybiformis due to the golden yellow cheilocystidia is I. alienospora (Corner & E. Horak) Garrido ( Horak 1980) reported from Singapore. Microscopically, this latter species is distinctly separated from the two aforementioned taxa by basidiospores with nodulose or flange-like projections. Similar cheilocystidia with yellow plasmatic pigment have been observed in Australian collections of I. lasseroides (E. Horak) Garrido (Matheny & Bougher, pers. comm.). Horak (1979) did not report this feature from material collected in Papua New Guinea.

Sequences of this species from Thailand form a robust monophyletic group ( Fig. 1 ). Inocybe hydrocybiformis may be most closely related to I. stellata groups I and II (see below) and I. lasseri Dennis , the latter described from the neotropics. However, this arrangement is weakly supported.

Figures

FIGURE 1. nLSU ML phylogeny of the Inocybaceae (with outgroups pruned) illustrating the autonomous placement and highly polyphlyetic nature of Thai and Malay species of Inocybe in bold (note that I. petchii and I. gemina are not present in the tree). Numbers above and below branches represent ML bootstrap values.

FIGURE 8. Macroscopic and anatomical features for Inocybe hydrocybiformis (ZT10077). a. Basidiomes. b. Basidiospores. c. Basidia. d. Cheilocystidia. e. Caulocystidia. f. Pileipellis. g. Basidiomes (ZT78-47, holotype). Scale bars: basidiomes = 20 mm, basidiospores = 10 μm, basidia and cystidia = 20 μm, pileipellis = 40 μm. Drawings by Egon Horak.

PLATE 8. SEM images. a. Basidiospores of Inocybe hydrocybiformis (ZT10077); scale bar = 2 μm. b. Basidiospores of Inocybe stellata (ZT10097, holotype); scale bar = 2 μm. c. Basidiospores of Inocybe thailandica (DED8049, holotype); scale bar = 5 μm. d. Hymenial cystidia of Inocybe angustifolia (ZT10149); scale bar = 10 μm. e. Basidiospores of Inocybe brevisquamulosa (ZT10102, holotype); scale bar = 2 μm. f. Basidiospores of Inocybe pusillima (ZT10130); scale bar = 2 μm. g. Basidiospores of I. fragilissima (DED8061, holotype); scale bar = 2 μm. h. Basidiospores of Inocybe ornata (ZT10107, holotype); scale bar = 3 μm. i. Basidiospores of Inocybe parvibulbosa (ZT10099, holotype). Scale bar = 2 μm. Photos by U. Jauch & M Kirchmair.