Hohenbuehelia flabelliformis Phonemany & Raspé
Faces of fungi number: FoF 10708, MycoBank: MB 843984
Pileus 35–45 × 20–40 mm, spathulate when young, expanding to spathuliform, flabelliform, rounded flabelliform, or orbicular, white when young, becoming yellowish white to pale yellow (4A2–4A3) at the center and cream (2A3–2B3) to slightly darker elsewhere in age; surface densely villose with white hairs that are longer near the attachment and shorter towards the margin, as observed with a lens; margin white, incurved when young, becoming straight when old. Lamellae 1–3 mm wide, decurrent, pale yellow to yellowish white (4A3–4A2), moderately crowded when mature, with lamellulae in 1–3 tiers; edge concolorous to sides, fimbriate. Stipe absent or as pseudostipe 5–12 mm × 3–8 mm. Context consisting of two layers: 1) non-gelatinous layer, 1 mm thick, soft when young and rather leathery when old, white to dirty white (4A1–4A2); 2) gelatinous layer 0.5 mm thick, soft, sticky, colorless. Odor mild, pleasant. Taste none. Spore print white. Basidiospores [150/3/2] (5.8–)6–7–8(–8.6) × (3.5–)4–4.2–5(–5.1) µm, Q = (1.3–)1.36–1.67–2.01(–2.03), ellipsoid to elongate (oblong) in side view, smooth, thin-walled, inamyloid. Basidia (21–)21–25.8–35(–37) × (5–)5.3–7.3–10.5(–11) µm, subclavate to clavate, with 4 sterigmata 4–8 µm long, hyaline, smooth, thin-walled. Cheilocystidia absent. Pleurocystidia metuloidal, present on both sides of lamellae and visible with a lens, (34–)34–42–54(–55) × (8.5–)8.5–11–14(–14.5) µm, scattered, narrowly fusiform to fusiform, mucronate at apex, brownish in KOH. Hymenophoral trama irregular, hyphae 2–5 µm wide. Pileipellis a trichoderm, hyaline in KOH, brownish in water, with cylindrical terminal elements 34–86 × 4–7 µm. Pileoleptocystidia absent. Pileus trama consists of two different layers: 1) upper layer gelatinous, composed of horizontally arranged, smooth, colorless encrusted hyphae, 2–5 µm wide; 2) lower layer, non-gelatinous, composed of interwoven, smooth, hyaline hyphae, 2–4 µm wide. Clamp connections present in pileipellis, pileus trama, and hymenophoral trama.
Habitat and distribution. On dead wood, scattered or fasciculate by 2–4 basidiomata. So far only found in tropical forests of northern Thailand.
Additional specimens examined. Thailand. Chiang Rai Province, Pa Daed District, Pa Ngae Village, 9 August 2019, Monthien Phonemany (MFLU22-0009).
Notes. The basidiomata colour of Hohenbuehelia flabelliformis is similar to H. angustata (Berk.) Singer, H. bonii A.M. Ainsw., H. concentrica Corner, H. carlothornii Consiglio, Setti & Thorn, H. horrida (Boedijn) Corner, H. luteola G. Stev, H. malesiana Corner, H. odorata C.K. Pradeep & Bijeesh, H. olivacea Yu Liu & T. Bau, and H. testudo (Berk.) Pegler. The basidiomata range from white, yellowish-white, yellow-brown, to pinkish-orange, and are spathulate to flabelliform. Hohenbuehelia angustata, originally described from Brazil, differs from H. flabelliformis by its smaller, smooth, greyish-yellow basidiomata, with stipe 4.5 mm long, smaller basidiospores (3.5–5× 2.5–3.5 μm), smaller cheilocystidia, and the presence of pileocystidia (Silva-Filho and Cortez 2017). H. horrida and H. odorata differ from H. flabelliformis by smaller basidiospores (5.2–7.6 × 4.8–6.4 μm), lack of cheilocystidia, and presence of pileoleptocystidia (Bijeesh et al. 2019). Hohenbuehelia testudo differs by smaller basidia (20–25 × 5–6 μm), larger pleurocystidia (44–78 × 12–18 μm) with thick yellowish walls, and the presence of cheilocystidia (Corner 1994). Hohenbuehelia malesiana, described from Brazil, is different from H. flabelliformis by having longer, subcylindrical basidiospores (7–9 × 3.5–4 μm), pileipellis as an interrupted cutis, and presence of cheilocystidia (Corner 1994). Hohenbuehelia bonii, from England, has larger yellow-brown basidiomata (20–75 mm diam.), smooth pileus surface, larger basidiospores (7.2–10.4 × 4.5–6.1 μm), larger pleurocystidia (56–103 × 11–19 μm), and an ixotrichoderm or ixocutis pileipellis (Ainsworth et al. 2016). Hohenbuehelia carlothornii described from Costa Rica, is different by having offwhite basidiomata with a large pseudostipe (20–32 × 14–25 mm), presence of cheilocystidia (Consiglio et al. 2018b). Hohenbuehelia concentrica from Singapore, has larger basidiomata (80 mm wide), larger basidiospores (8–8.5 × 6–6.7 μm), and absence of cheilocystidia (Corner 1994). Hohenbuehelia incarnata, from the Solomon Islands, differs from H. flabelliformis by subglobose basidiospores and the presence of subcylindrical to submoniliform cheilocystidia (Corner 1994). Hohenbuehelia olivacea, originally described from China, has reniform basidiomata with dense and long tomentum, light brown to pallid brown in gelatinous zone, and the presence of cheilocystidia (Liu and Bau 2009). Phylogenetically, H. flabelliformis was closely related to H. algonquinensis Consiglio, Setti & Thorn. (voucher RGT 870601/12 UWO) with 3.5% (21/599) differences in the ITS sequence, 1.4% (12/839) in the LSU sequence, and 6.66% (35/540) in the tef1 sequence. Moreover, the morphologies of both species are completely different, with H. algonquinensis having glossy black pileus, ungulate to dimidiate basidiomata and contrasting white or off-white lamellae (Consiglio et al. 2018b).
Fig. 1 Phylogeny of selected sequences of Hohenbuehelia based on a maximum likelihood analysis of three nuclear gene regions (nrITS, nrLSU, tef1). The Maximum likelihood bootstrap values (BS ≥ 70%) and Bayesian posterior probabilities values (PP ≥ 0.90) are shown on the branches. Newly sequenced collections are in bold. Five Pleurotus species were used as outgroup. (T) designates holotypes. The sequence H. flabelliformis voucher number MFLU22-0008 was identical to MFLU22-0009 (ITS only). Sequences of H. lageniformis voucher number MFLU22-0010 were identical to MFLU22-0012 (ITS and LSU). Sequences of H. tristis subsp. macrocarpa voucher number MFLU22-0016 were identical to MFLU22-0015 (ITS and LSU) and to the two specimens MFLUCC 12-0451 and HFJAU0029 identified as H. grisea (both only ITS) from GenBank, except for three substitution heteromorphisms in the ITS sequence of MFLU22-0016.