Inocybe brevisquamulosa 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 : 221-223

13. Inocybe brevisquamulosa E. Horak, Matheny & Desjardin , spec. nov. Fig. 12a–f ; Pl. 8e

MycoBank MB 519911

Etymology: brevis (Lat.), short; squamulosus (Lat.), squamules.

Diagnosis: Basidiomes very small and delicate. Pileus 6–10 mm wide, papilla or umbo absent, surface densely covered with suberect to scurfy scales, cinnamon brown to pale umber brown. Stipe 12–18 × 1 mm, equal with a slightly swollen base, concolorous with the pileus, minutely fibrillose all over (not pruinose), veil remnants absent. Odor not distinctive. Basidiospores 8.5–10 × 5.5–6 μm, distinctly nodulose. Cheilocystidia and pleurocystidia 30–50 × 12–17 μm, utriform, with hyaline walls up to 2.5 μm thick. Caulocystidia absent. In lowland tropical forest dominated by Dipterocarpaceae , Thailand.

Holotype:— THAILAND. Mae Hong Son Prov.: S of Mae Hong Son, Hwy. 108, at 247 km marker, 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 (ZT10102, holotype) GenBank accession no. GQ893019, GQ892974.

Pileus 6–10 mm wide, at first hemispherical, convex in age, papilla or umbo absent; cinnamon brown to pale umber brown; disc densely covered with rather coarse, concolorous, suberect to scurfy squamules, coarsely innate-fibrillose towards non-striate margin, dry, veil remnants absent. Lamellae 24–32 reaching stipe, 3 (–7) lamellulae, adnexed, ventricose, up to 1.5 mm wide, cinnamon brown to umber brown, edges white and fimbriate. Stipe 12–18 × 1 mm, cylindrical, equal, base slightly swollen (up to 1.5 mm diam), concolorous or paler as pileus, also at base, minutely fibrillose all over (not pruinose), dry, solid; veil remnants absent; context concolorous, not reddening. Odor and taste not distinctive.

Basidiospores 8.5–10 × 5.5–6 μm, ovoid, distinctly nodulose, yellow-brown, brown in deposit. Basidia 20–26 × 7–8 μm, 4-spored, clavate or urniform. Cheilocystidia 30–50 × 12–17 μm, utriform, metuloid, walls up to 2.5 μm thick at apex, hyaline, crystals present; paracystidia absent. Pleurocystidia similar to cheilocystidia. Caulocystidia absent, surface covered with loose, hyaline, thin-walled, cylindrical hyphae, 4–6 μm wide, terminal cells gradually tapering towards blunt apex, hyaline wall encrusted. Pileipellis a trichoderm of erect, cylindrical hyphae, 6–14 μm wide, terminal cells distinctly conical towards apex, non-gelatinized, thin-walled, strongly encrusted with yellow-brown pigment; subcutis hyphae cylindrical, 10–20 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 ), 425 m elev.

Known distribution: Northwest Thailand.

Notes: The basidiomes of I. brevisquamulosa are very small and delicate. Accordingly, this rarely encountered taxon is easily overlooked or can be mistaken readily for one of the two other phenetically similar Thai representatives of Inocybe , viz., I. pusillima or I. fragilissima . Macroscopically, however, I. brevisquamulosa can be identified in the field by the minutely squamulose pileus. Furthermore, this taxon is characterized by rather large nodulose basidiospores (the largest of the three aforementioned sympatric taxa) and the broadly utriform metuloid cheilocystidia and pleurocystidia. No distinctive caulocystidia occur on the stipe. Inocybe brevisquamulosa was discovered only once occurring on soil among ashes and charcoal after a recent forest fire under dipterocarps.

Phylogenetic analysis ( Fig. 1 ) places I. brevisquamulosa (type) sister to sect. Calosporae but with poor bootstrap support. Inocybe brevisquamulosa , unlike members of sect. Calosporae , lacks a pruinose stipe and has distinctly nodulose spores, rather than globose spinose spores.

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 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 12. Macroscopic and anatomical features for Inocybe brevisquamulosa (ZT10102, holotype). a. Basidiomes. b. Basidiospores. c. Basidia. d. Cheilocystidia and pleurocystidia. e. Caulocystidia. f. Pileipellis. Scale bars: basidiomes = 20 mm, basidiospores = 10 μm, basidia and cystidia = 20 μm, pileipellis = 40 μm. Drawings by Egon Horak.