Inocybe latibulosa 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 : 207-208

3. Inocybe latibulosa E. Horak, Matheny & Desjardin , spec. nov. Fig. 4a–h ; Pl. 2a

MycoBank MB 519914

Etymology: latibulosus (Lat.), hiding.

Diagnosis: Fruitbodies very small. Pileus 3–5 mm wide, conspicuously velutinous all over, texture soft. Lamellae distant. Stipe 8–12 × 0.5–1 mm, subpruinose at apex, cortina absent. Odor not distinctive. Basidiospores amygdaliform, smooth. Cheilocystidia and pleurocystidia thin-walled. On soil in tropical montane forest dominated by Castanopsis in Thailand.

Holotype:— THAILAND. Chiang Mai Prov.: Mae Sae, Hwy 1095, at 55 km marker, N19˚14‘32.6“, E98˚38 ‘29.4“, 990 m elev., on soil in tropical montane forest (dominated by Castanopsis ), 10 Jun. 2006, leg. T. Osmundson & D. E. Desjardin ( DED8055 , holotype, SFSU; isotype ZT13026 ) GenBank accession no. GQ892992, GQ892946.

Pileus 3–5 mm wide, obtusely conical, convex or convex with a low and broad umbo, conspicuously velutinous all over, dark brown (6F5–8), dull, dry, veil remnants absent; context <0.5 mm thick, unchanging on exposure, soft (not Inocybe -like). Lamellae (16–) 20–28 reaching stipe, 1–3 lamellulae, adnexed, rather distant, up to 1.5 mm wide, pale brown (7D4), fimbriate edges concolorous or whitish. Stipe 8–12 × 0.5–1 mm, central, cylindrical, equal, pale brown (7D5–6) overall, subpruinose at apex, minutely fibrillose towards base, dry, solid; cortina absent. Odor and taste not distinctive.

Basidiospores 7.5–9 × 5–5.5 μm, distinctly amygdaliform, brown, smooth, occasionally with obscure germ pore, brown in deposit. Basidia 24–30 × 7–9 μm, 4-spored (occasionally 2-spored), clavate. Cheilocystidia 45–55 (–60) × 12–20 μm, subfusoid or lageniform, wall thin (<0.5 μm thick), hyaline, crystals absent or scattered; paracystidia 20–35 × 15–22 μm, broadly clavate or subglobose, conspicuous, wall thin, hyaline. Pleurocystidia similar to cheilocystidia. Caulocystidia 35–65 × 6–12 μm, polymorphic, shape ranging from cylindrical to subfusoid, wall thin, occasionally encrusted with brown pigment. Pileipellis a distinctive trichoderm of suberect chains of short-globose or ovoid cells, 20–34 μm wide; terminal cells 20–50 × 6–10 μm, slender fusoid or conical, non-gelatinized wall strongly encrusted with dark brown pigment; subpellis hyphae globose or ovoid, wall occasionally up to 1 μm thick; oleiferous hyphae absent. Clamp connections present.

Habitat: On soil in tropical montane forest (dominated by Castanopsis ), 990 m elev.

Known distribution: Northwest Thailand.

Other specimen examined: THAILAND. Chiang Mai Prov.: same location as holotype, 10 Jun. 2006, leg. H.T. Le & D. E. Desjardin ( DED8054 b, SFSU; ZT13027 ) GenBank accession no. GQ906702, GQ892947 .

Notes: The basidiomes of Inocybe latibulosa are remarkably small and thus macroscopically the habit is reminiscent of a species of Flammulaster or Phaeomarasmius . Microscopical analysis, however, reveals distinctive and for Inocybe typical features, viz., pleurocystidia occasionally encrusted with crystals and large hyaline vesiculose paracystidia at the lamellar edges. In addition, this species is well characterized by the trichodermal pileipellis composed of suberect chains of short-globose or ovoid cells with distinctive slender fusoid or conical terminal cells.

Inocybe latibulosa is only one of two smooth-spored species with pleurocystidia that we describe from Thailand. A portion of DED8054 (DED8054b) is conspecific with the type. The phylogenetic position of I. latibulosa is not strongly placed, but the ML tree ( Fig. 1 ) suggests the species is related to other smooth-spored species of Inocybe , as well as the weakly nodulose-spored I. albodisca Peck recorded from the west coast of North America.

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.

PLATE 2. a. Inocybe latibulosa (DED8055, holotype). b. Inocybe neglecta (DED8063, holotype). c. Inocybe errata (ZT10108, holotype). d. Inocybe proxima (DED8007, holotype). Scale bars = 10 mm. Photos a, b, d, by Dennis Desjardin, c, by Egon Horak.

FIGURE 4. Macroscopic and anatomical features for Inocybe latibulosa (DED8055, holotype). a. Basidiomes. b. Basidiosores. c. Basidia. d. Cheilocystidia. e. Paracystidia. f. Pleurocystidia. g. Caulocystidia. h. Pileipellis. Scale bars: basidiomes = 20 mm, basidiospores = 10 μm, basidia and cystidia = 20 μm, pileipellis = 40 μm. Drawings by Egon Horak.