Inocybe stellata 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 : 215-218

10. Inocybe stellata E. Horak, Matheny & Desjardin , spec. nov. Fig. 9a–g ; Pl. 3b–d , 8b

MycoBank MB 519921

Etymology: stellatus (Lat.), star-like, referring to the shape of the basidiospores.

Diagnosis: Pileus conical or cuspidate, expanding with a distinctive papilla, dark brown or fuscous brown, papilla drying yellow-brown or pale ochre, center of surface with recurved scales, veil remnants appendiculate on the margin but not persisting with age, context tough, not changing upon exposure. Stipe slender, base equal or slightly swollen; surface dry, densely covered with conspicuous whitish or concolorous fibrils often forming appressed belts or zones. Odor not distinctive. Basidiospores 12–16 μm wide, globose to subglobose, with distinct conical and/or saddle-shaped projections. Cheilocystidia and pleurocystidia 35–50 × 15–20 μm, utriform or broadly fusoid, walls 1–2 μm thick, apices with crystals. In tropical lowland forest dominated by Dipterocarpaceae and in tropical montane forest dominated by Quercus , Lithocarpus , Castanopsis , with scattered Pinus kesiya , Thailand and Bangladesh.

Holotype:— THAILAND. Mae Hong Son Prov.: south of Mae Hong Son, Hwy. 108, at 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 ZT10097 (SFSU, holotype; ZT, isotype) GenBank accession no. GQ893008, GQ892963.

Pileus 8–25 (–35) mm wide, at first distinctly conical or cuspidate, gradually expanding with distinctive conical or cuspidate papilla; dark brown (6E–F5–8) or fuscous brown (6E5–8) overall, on drying papilla turning yellow-brown or pale ochre, occasionally with faint reddish tinge; with small recurved, concolorous squamules or small scales at center, with radial, appressed whitish fibrils or appendiculate, non-persisting veil remnants towards rimose margin, dry, veil remnants absent in old specimens; context tough, concolorous or buff, unchanging upon exposure. Lamellae 32–40 reaching stipe, 3–7 (–15) lamellulae, adnexed or sinuate, ventricose, up to 3.5 mm wide; at first pale grey-brown (5C3), becoming dark brown (6E7–8) or chocolate brown in age, occasionally with rusty tinge; edges subfimbriate, concolorous or whitish. Stipe 35–70 (–120) × 1.5–2 mm, central, cylindrical, slender, equal or base slightly swollen (up to 5 mm diam); surface dry, densely covered with conspicuous whitish or concolorous fibrils often forming appressed belts or zones, subpruinose at apex only, pale grey-brown (6C3) or brown (6E5–8), reddish tinge absent, with white tomentum covering base; cortina present in youth; context solid or hollow. Odor not distinctive (or mildly rancid or astringent). Taste not distinctive.

Basidiospores (10–) 12–16 μm (including conical and/or saddle-shaped projections, up to 3 μm long), globose or subglobose, brown, also brown in deposit. Basidia (25–) 30–40 × 10–13 μm, 4-spored, clavate or subcylindrical. Cheilocystidia (30–) 35–50 × 15–20 μm, utriform or broadly fusoid, metuloid, wall thick (1–2 μm) or thin, hyaline, crystals present; paracystidia 14–25 × 10–15 μm, clavate or vesiculose, thin-walled, hyaline. Pleurocystidia similar to cheilocystidia. Caulocystidia scattered, similar to cheilocystidia, present at stipe apex only. Pileipellis a trichoderm or cutis of cylindrical hyphae, 4–7 μm wide, terminal cells not differentiated, non-gelatinized wall encrusted with brown pigment; subpellis of cylindrical, short-celled hyphae, 8–12 μm wide, encrusted with brown pigment; oleiferous hyphae scattered. Clamp connections present.

Habitat: Singly on lateritic soil in tropical lowland forest (dominated by Dipterocarpus obtusifolia , mixed with Tectona grandis ) and in tropical montane forest (dominated by Quercus , Lithocarpus , Castanopsis , with scattered Pinus kesiya ), 425–1200 m elev.

Known distribution: Northwest Thailand (type), Bangladesh.

Other specimens examined: BANGLADESH. Rangpur Division: Dinajpur, Birganj, Singra Forest, N25°52‘33.04“, E88°33‘347.28“, 4 Jul. 2013, M.I. Hosen 746 (SHAF 6). THAILAND. Chiang Mai Prov.: Doi Suthep, Sangasabhasri Lane, 1200 m elev., on lateritic soil in tropical montane forest (dominated by Quercus , Lithocarpus , Castanopsis ), 4 Jul. 2002, leg. E. & A. Horak (ZT10123) GenBank accession no. GQ893009, GQ892965; Hwy 1095, at 22 km marker, N19˚07‘57.0‘‘, E98˚45‘64.7‘‘, on soil in tropical submontane forest (dominated by Dipterocarpus ), 4 Jun. 2006, leg. H.T. Le & D.E. Desjardin (DED8015, SFSU; ZT13028) GenBank accession no. GQ893011, GQ892966; same locality and habitat, 4 Jun. 2006, leg. H.T. Le & D.E. Desjardin (DED8060, SFSU; ZT13029) GenBank accession so. GQ893010, GQ892965; Hwy 1095, at 22 km marker, N19˚07‘570‘‘, E98˚45‘647‘‘, 750 m elev., on soil in tropical submontane forest (dominated by Dipterocarpus , Castanopsis , with scattered Pinus kesiya ), 30 Jun. 2007, leg. D.E. Desjardin (DED8162, SFSU) GenBank accession no. GQ893006, GQ892961; Hwy 1095 near 27 km marker, Pathummikaram Temple area, Ban Pha Deng, N19˚06‘28.8‘‘, E98˚44‘47.3‘‘, 1050 m elev., on soil in tropical montane forest (dominated by Dipterocarpus ), 19 Jul. 2007, leg. E.C. Vellinga 3648 (SFSU) GenBank accession no. GQ893012, GQ892967; same locality and habitat, 19 Jul. 2007, E.C. Vellinga 3651 (SFSU) GenBank accession no. GQ893007, GQ892962.

Notes: Inocybe stellata is frequently encountered in tropical lowland and tropical montane forests in northwest Thailand and Bangladesh dominated by Dipterocarpus and fagalean trees ( Quercus , Lithocarpus , Castanopsis ). The identification of I. stellata must be supported by a molecular analysis as the morphological features (macroscopic and microscopic) of the basidiomes are not sufficient. Indeed, two separate clades of I. stellata are recovered as weakly supported sister taxa: clade I [DED8162, ECV3651, ECV3648, ZT10097 (type; Pl. 3c )]; and clade II [DED8015, ZT10123 ( Pl. 3b ), DED8060 ( Pl. 3d )]. Unpublished sequences of rpb2 from DED8015, DED8060 and DED8162, ECV3651 also support the distinction between the two clades (data not shown). At this point we prefer to label these as two distinct lineages (similar to treatment of Paxillus involutus by Vellinga et al. 2012) within the morphological species I. stellata . Additional collections and future work will be necessary to determine the extent of morphological, ecological, and genetic variation within I. stellata . Large basidiomes of I. stellata are readily confused with small specimens of I. petchii , I. gemina and/or I. echinosimilis (E. Horak) Garrido ( Horak 1980) , which are already recorded or expected to occur either in Thailand or Malaysia.

Figures

PLATE 3. a. Inocybe gemina (ZT72-425, holotype). b. Inocybe stellata clade II (ZT10123). c. Inocybe stellata clade I (ZT10097, holotype). d. Inocybe stellata clade II (DED8060). Scale bars = 10 mm. Photos a, b, c, by Egon Horak, d, by Dennis Desjardin.

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 9. Macroscopic and anatomical features for Inocybe stellata clade II (DED8060). a. Basidiomes. b. Basidiospores. c. Basidia. d. Cheilocystidia. e. Pleurocystidia. f. Caulocystidia. g. Pileipellis. Scale bars: basidiomes = 20 mm, basidiospores = 10 μm, basidia and cystidia = 20 μm, pileipellis = 40 μm. Drawings by Egon Horak.