Inocybe parvibulbosa 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 : 229-230

18. Inocybe parvibulbosa E. Horak, Matheny & Desjardin , spec. nov. Fig. 17 :a–i; Pl. 5c–d , 8i

MycoBank MB 519918

Etymology: parvus (Lat.), small; bulbosus (Lat.), bulbous.

Diagnosis: Similar to Inocybe lineata but I. parvibulbosa differs by the smaller basidiomes (pileus 6–18 mm wide, stipe 15–30 × 1–1.5 mm), broader basidiospores, and the pileipellis structure: a cutis of non-gelatinized or weakly gelatinized hyphae in I. parvibulbosa , a trichoderm or cutis of erect or repent, non-gelatinized hyphae in I. lineata . Pileus smooth or minutely scaly over the disc, weakly splitting or rimose towards the margin. Stipe slender, entirely pruinose, with a distinct marginate bulb, cortina absent. Basidiospores 8.5–10.5 × 8–9.5 μm, ovoid, distinctly nodulose, with hemispherical or obtuse-conical projections. Cheilocystidia, pleurocystidia, and caulocystidia 40–60 (–70) × 12–20 (–24) μm, broadly fusoid or utriform; walls mostly hyaline, up to 4–5 μm thick. In tropical lowland and montane mixed dipterocarp, fagalean, conifer forests, Thailand and Papua New Guinea.

Holotype:— THAILAND. Mae Hong Son Prov.: S of Mae Hong Son: Hwy. 108, 247 km marker, ca. 425 m elev., on lateritic soil (in recently burned) tropical submontane forest (dominated by Dipterocarpus obtusifolia , mixed with Tectona grandis ), 1 Jul. 2002, leg. E. & A. Horak (ZT10099, holotype) GenBank accession no. GQ893000, GQ892955.

Pileus 6–18 mm wide, at first obtuse-conical, becoming convex, campanulate or plane with depressed obtuse umbo in age, cinnamon brown, dark hazel brown (6E5–6) or fuscous, paler towards margin, smooth or minutely squamulose at disk, coarsely innately fibrillose towards weakly splitting or rimose margin, young specimens occasionally with greyish velipellis over disk, subviscid if moist, veil remnants at margin absent. Lamellae 36–52 reaching stipe, 3–7 lamellulae, close to crowded, adnate to adnexed, ventricose, up to 2 mm broad; at first greyish brown, cinnamon brown, becoming dark brown with rusty tinge or umber brown in age; edges fimbriate and white. Stipe 15–30 × 1–1.5 (–2) mm, cylindrical, equal above, but base with distinctive marginate, cup-shaped bulb, up to 3.5 mm wide; surface dry, pruinose all over, whitish to pallid brown, dark brown in old specimens; cortina absent; context solid, whitish, not reddening upon exposure. Odor not distinctive or weakly spermatic. Taste not distinctive.

Basidiospores 8.5–10.5 × 8–9.5 μm, ovoid, distinctly nodulose, hemispherical or obtuse-conical projections (nodules) 2–2.5 μm high, yellow-brown, brown in deposit. Basidia 20–34 × 7–10 μm, 4-spored, clavate. Cheilocystidia 40–60 (–70) × 12–20 (–24) μm, broadly fusoid or utriform, with hyaline or sometimes yellow-brown metuloid walls, up to 4–5 μm thick at apex, crystals present; paracystidia (10–) 15–30 × 7–15 μm, vesiculose or clavate, numerous, with hyaline thin walls, pigment absent. Pleurocystidia size and shape like cheilocystidia. Caulocystidia size and shape like cheilocystidia, but less metuloidal, intermixed with clavate, thin-walled cells. Pileipellis an (ixo)cutis of repent (or suberect) cylindrical hyphae, (2–) 4–8 (–10) μm wide, terminal cells not differentiated, non-gelatinized or weakly gelatinized wall encrusted with yellow-brown pigment; subcutis hyphae cylindrical, 6–12 μm wide, encrusted with pigment; oleiferous hyphae absent. Clamp connections present.

Habitat: On lateritic soil, in (recently burned) tropical lowland and montane mixed dipterocarp, fagalean, conifer forests (dominated by Dipterocarpus obtusifolia , mixed with Tectona grandis , Castanopsis spp , Pinus kesiya ), 425– 1000 m elev.

Known distribution: Papua New Guinea, Northwest Thailand (type).

Other specimens examined: 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 tropical submontane mixed dipterocarp and conifer forest ( Dipterocarpus obtusifolia , Pinus kesiya ), 29 Jun. 2002, leg. E. & A. Horak (ZT10078) GenBank accession no. GQ893001, GQ892956; S 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 (ZT10103) GenBank accession no. GQ893002. Chiang Mai Prov.: S of Mae Hong Son, Hwy. 108, at 247 km marker, ca. 425 m elev., on lateritic soil tropical lowland forest (dominated by Dipterocarpus obtusifolia , mixed with Tectona grandis ), 1 Jul. 2002, leg. E. & A. Horak (ZT10105) GenBank accession no. GQ893003, GQ892957; Hwy. 1095, at 22 km marker, N19˚07‘570‘‘, E98˚45‘647‘‘, on soil in tropical lowland forest (dominated by Dipterocarpus ), 4 Jun. 2006, leg. D.E. Desjardin (DED8021, SFSU; ZT13033) GenBank accession no. GQ892999, GQ892954. PAPUA NEW GUINEA. Morobe District: Wau, Mt Kaindi, on soil in tropical montane rain forest under Nothofagus carrii , 2300 m elev., 3 Jun. 1973, leg. E. Horak 73-299 (ZT).

Notes: The epithet of I. parvibulbosa refers to the distinctive marginate bulb at the base of the slender and entirely pruinose stipe. To date the species has been recorded six times and it can be speculated that in the Malayan tropical lowland and montane forests I. parvibulbosa is an obligate ectomycorrhizal partner of Dipterocarpus spp. and probably also Castanopsis spp.

Inocybe parvibulbosa represents a complex of genetically distinct lineages. The name is conservatively applied here as four different LSU sequences labeled I. parvibulbosa form a paraphyletic entity that gives rise to I. lineata (described below). All four are found in dipterocarp associations or in forests with dipterocarps present. Together, LSU sequences of I. parvibulbosa and I. lineata form a strongly supported clade. More field data and sequences from alternative loci, we believe, are required to better interpret the extent of morphological and genetic variation in this complex. For further discussion refer to I. lineata .

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.

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.

FIGURE 17. Macroscopic and anatomical features for Inocybe parvibulbosa (ZT10099, holotype). a. Basidiomes. b. Basidiospores. c. Basidia. d. Cheilocystidia. e. Paracystidia. f. Caulocystidia. g. Pileipellis. h. Basidiospores (ZT13033). Scale bars: basidiomes = 20 mm, basidiospores = 10 μm, basidia and cystidia = 20 μm, pileipellis = 40 μm. Drawings by Egon Horak.