Hymenopellis utriformis

Hymenopellis utriformis Niego & Raspé

MycoBank No: 845751, Facesoffungi Number: FoF12895

Basidiomata small-sized to large. Pileus 25–95 mm diam., circular in polar view, in side view broadly convex to plane to slightly depressed, light brown (5C5), moist to viscid, non-hygrophanous, rugose surface, radially wrinkled with age; margin plane to decurved, translucent striate; context cream (1A3) to white, unchanging when cut, consistency rubber-like. Lamellae 4–8mm broad, adnexed, ventricose, white to cream (1A3), spacing > 1 mm; lamellar margin even; lamellulae present, in 2 tiers. Stipe 50–185 mm × 4–12 mm, central, cylindrical, mostly equal, thickened at the base, off-white to light brown (5A2) from the pileus becomes darker (5D4) towards the base, surface dry, appressed squamulose especially towards the base, narrowly fistulose; context white, unchanging when cut; pseudorrhiza present. Annulus and volva absent. Spore print white. Smell indistinct. Taste slightly sweet. Basidiospores [60,3,1] (11.7) 12–13.7– 16.7 (17) × (9.3) 10.1–11.4–12.6 (12.7) µm (Q = 1.0–1.5, Q* = 1.2), subglobose to ellipsoid, thin-walled, hyaline in 5% KOH. Basidia [30,3,1] (36) 36.7–38.1–39.2 (39.5) × (9.4) 11.3–11.6–12.8 (13) µm (Q = 3.0–4.0, Q* = 3.3), 2–spored, clavate, without clamp connection. Cheilocystidia [30,3,1] (31) 38–52–64 (67.7) × (8.6) 9–13.2–18 (18.5) µm (Q = 3.1–5.0, Q* = 3.9), numerous, grouped together, pedunculate, narrowly clavate to clavate, conical, narrowly utriform to utriform, smooth, thin-walled, hyaline in 5% KOH. Pleurocystidia [30,3,1] (83) 88–116.3–131 (174) × (22) 22.5–30–35 (37.5) µm (Q = 2.9–5.4, Q* = 3.9) scattered, narrowly utriform to utriform, smooth, thin-walled, hyaline in 5% KOH. Hymenophoral trama irregular, made of thin-walled, hyaline hyphae. Pileipellis an epithelioid hymeniderm; terminal elements 28–52–76 × 11–13.7–17.5 µm with few scattered intracellular light brown (6D8) pigment in 5% KOH. Stipitipellis a trichoderm, terminal elements 28–52–76 × 11–13.7–17.5 µm, with intracellular light brown (6D8) pigment in 5% KOH. Clamp connections not seen.

Habitat and distribution: Solitary to clustered, in soil covered with degrading leaves and other organic matters, in deciduous forest of Chiang Mai Province, Thailand.

Additional specimen examined: Thailand. Chiang Mai Province: Mae Taeng District, elev. 375 m, tropical deciduous forest, 09 August 2019, A.G. Niego, MFLU22-0141; GenBank OP265165-ITS, OP265160-nrLSU.

Notes: Hymenopellis utriformis is similar to H. rubrobrunnescens (Redhead, Ginns & Shoemaker) R.H. Petersen, having small to large but gracile basidiomata. The color is “tawny olive” (5C5) with rugose to rugulose surface. Hymenopellis radicata (Relhan) R.H. Petersen, as described by Petersen and Hughes (2010), is similar to H. utriformis in having large basidiomata and a mid-brown (5–6D, 5–6E5–8, 5E7, 4E7, 6D3) pileus which is radially wrinkled. Both species are rather moist to viscid. However, H. radicata stipe is longitudinally lined, usually twisted while its cheilocystidia are clavate to subcapitate when young, broadly cylindrical, jar-shaped to occasionally mammillate when mature. The cheilocystidia of H. utriformis were more diverse in shapes. Pleurocystidia of H. radicata are strongly inflated, bluntly rounded to hemispherical apically, narrowly utriform to utriform whereas H. utriformis have narrowly utriform to utriform pleurocystidia only. Other species similar to H. utriformis found in Asia are H. furfuracea and H. raphanipes, both having medium to large basidiomata but with more diverse pileal colors (Petersen and Hughes 2010). Hymenopellis furfuracea basidia are tetrasporic while those of Hymenopellis raphanipes can be 2-spored, except for the synonymized H.chiangmaiae, which is the tetrasporic form from Asia. Hymenopellis utriformis basidia, however, are strictly 2-spored.

Fig. 1 Phylogenetic tree generated from ML analysis of combined ITS and nrLSU data set for Hymenopellis with three outgroup species. Bootstrap support values (≥70%) and posterior probabilities (≥0.9) (BS/PP) are given above the branches. All termini are with species name and voucher ID, with the newly generated sequences from this study in bold.