Inocybe sphaerospora Kobayasi (1952: 80)

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 : 204-206

1. Inocybe sphaerospora Kobayasi (1952: 80) Fig. 2a–g ; Pl. 1a–b

Pileus 45–60 mm wide, at first convex, expanded flat, center depressed or with shallow umbo in age, non-striate margin decurved with non-persisting fibrillose veil remnants, at disc subglabrous, towards margin radially appressed-fibrillose, dry, velipellis absent, splitting in age; deep (chrome) yellow (2A5–6) or pale (lemon) yellow (3A3) overall. Lamellae 42–60 reaching stipe, up to 15 lamellulae, adnexed to adnate, up to 10 mm wide, at first bright yellow, turning to greyish yellow (3–4B4–5) and finally dark greyish yellow (4C6–8) in age, entire edges concolorous. Stipe 45–60 × 8–9 mm, central, cylindrical, ± equal, bright yellow (2A5–6) overall, subpruinose (at apex), glabrous or fibrous towards base, dry, solid; cortina present in young specimens, absent in mature material; context 1–2 mm thick, pale yellow (2A2–3), unchanging on exposure. Odor not distinctive. Taste not distinctive.

Basidiospores 5.5–6 × 5–5.5 μm, subglobose, yellow-brown, smooth, brown in deposit. Basidia 24–30 × 6–8 μm, 4-spored, clavate. Cheilocystidia 30–65 (–75) × 10–18 (–20) μm, slender fusoid or lageniform, weakly metuloid, wall 0.5–1.5 μm thick at apex, hyaline, crystals absent or scattered; paracystidia absent. Pleurocystidia scattered, similar size and shape as cheilocystidia. Caulocystidia 30–60 × 8–12 μm, present at the apex only, shape ranging from subclavate to fusoid, hyaline, thin-walled, occasionally submetuloid at apex. Pileipellis a cutis of repent, cylindrical hyphae, 3–5 μm wide, terminal cells not differentiated, subgelatinized wall thin; subpellis hyphae cylindrical, 6–10 mm wide, minutely encrusted with pale yellow pigment; oleiferous hyphae absent. Clamp connections present.

Habitat: On soil in tropical lowland or submontane forest (dominated by Dipterocarpus , Anisoptera , Quercus ) and tropical montane forest (dominated by Castanopsis , Lithocarpus , Quercus , with scattered Pinus kesiya ), 750–1050 m elev.

Known distribution: Japan (type), Papua New Guinea ( Horak 1981), Singapore ( Horak 1981), Malaysia ( Turnbull 1995), Thailand.

Specimens examined: THAILAND. Chiang Mai Prov.: Hwy 1095, at 22 km marker, N19˚07.570‘, E98˚45.647‘, 750 m elev., on soil in tropical submontane or montane forest (dominated by Dipterocarpus ), 11 Jun. 2006, leg. R. Zhao & D.E. Desjardin (DED8059, SFSU; ZT13024) GenBank accession no. GQ892993, GQ892948 ( Fig. 1 ); Doi Inthanon National Park, Hwy 109, at 25 km marker, N18˚32‘19.5‘‘, E98˚33‘42.5‘‘, 1050 m elev., on soil in tropical montane broadleaf forest, under Pinus kesiya ), 28 Jun. 2007, leg. D.E. Desjardin (DED8153, SFSU) GenBank accession no. GQ892994, GQ892949 ( Fig. 2 ). MALAYSIA. Selangor: Kepong, Bukit Hari, trail to Waterfall, 200 m elev., tropical lowland forest (dominated by Castanopsis , Quercus ), 30 Aug. 2009, leg. E. Horak (ZT13248). PAPUA NEW GUINEA. Morobe District: Bulolo, Manki, on soil in tropical montane rain forest (dominated by Castanopsis , Lithocarpus ), 28 Mar. 1972, leg. E. Horak (ZT72-333). SINGAPORE. Singapore: Singapore Botanical Garden, in tropical lowland dipterocarp forest, leg. E.J.H. Corner s.n. (E, ZT 80-176).

Notes: Inocybe sphaerospora is an unique species characterized by yellow, medium-sized basidiomes and (rarely observed in the genus) subglobose basidiospores ( Horak 1981). It is widely distributed in southeast and east Asia ( Turnbull 1995), predominantly in dipterocarp and less often in fagalean forests where it was recorded from sea level to 1400 m elevation ( Papua New Guinea). The tricholomatoid yellow basidiomes of I. sphaeropora can be mistaken for I. lutea Kobayasi & Hongo ( Kobayasi 1952) , which both in Japan (type) and Papua New Guinea is considered to be in ectomycorrhizal association with Castanopsis and Lithocarpus . However, I. lutea is distinctly separated by the smaller yellow-orange basidiomes, the marginate stipe base and nodulose basidiospores ( Horak 1980). Kobayashi (2002) includes reference to I. hinoana Yukawa & Katum. , known only from its type locality in Japan, which differs by its larger (7–8.5 × 5–6.5 μm) ellipsoid spores.

We observed a large number of unambiguous LSU nucleotide differences (22) between the two Thai exemplars identified as I. sphaerospora based on morphology. These are visualized on the tree figure ( Fig. 1 ). DED8153 ( Pl. 1b ) also possesses a unique 27-bp insert in the LSU region. This sequence differentiation could correspond with ecological differences:DED8153 is a Pinus -associate, whereas DED8059 ( Pl. 1a ) is a dipterocarp-associate.Additional collections are needed to determine consistency of these genetic and ecological differences.

Figures

PLATE 1. a. Inocybe sphaerospora (DED8059). b. Inocybe sphaerospora (DED8153). Scale bars = 10 mm. Photos by Dennis Desjardin.

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.

FIGURES 2–3. 2. Macroscopic and anatomical features for Inocybe spherospora (DED8059). a. Basidomes. b. Basidiospores. c. Basidia. d. Cheilocystidia. e. Pleurocystidia. f. Caulocystidia. g. Pileipellis. 3. Macroscopic and anatomical features for I. bicolorata (ZT12187, holotype). a. Basidiomes. b. Basidiospores. c. Basidia. d. Cheilocystidia. e. Pileipellis. Scale bars: basidiomes = 20 mm, basidiospores = 10 μm, basidia and cystidia = 20 μm, pileipellis = 40 μm. Drawings by Egon Horak.