Lyomyces asiaticus Y. L. Deng & C. L. Zhao 2025, sp. nov.

Lyomyces asiaticus Y. L. Deng & C. L. Zhao sp. nov. Figs 8, 9, 10 Holotype. China • Yunnan Province, Xishuangbanna, Wild elephant Valley, GPS coordinates: 22°17'N, 100°85'E, altitude 900 m asl., on the dead bamboo, leg. C. L. Zhao, 25 January 2024, CLZhao 35719 (SWFC). Etymology. Asiaticus (Lat.): referring to the continent (Asia) where the species was found. Diagnosis. Lyomyces asiaticus is characterized by the membranaceous basidiomata with cream to pale-yellow hymenial surface with tuberculate, a monomitic hyphal system with clamped generative hyphae, and ellipsoid basidiospores 4.6–6.4 × 3–3.9 µm. Description. Basidiomata annual, resupinate, closely adnate, membranaceous, without odor or taste when fresh, up to 5 cm long, 1.5 cm wide, and 100 μm thick. Hymenial surface tuberculate, thin, white to cream when fresh, cream upon drying. Sterile margin white to cream, thinning out, up to 2 mm. Hyphal system monomitic; generative hyphae with clamp connections, colorless, thin-walled, smooth, moderately branched, with some crystals, 2–2.5 µm in diameter, IKI –, CB –, tissues unchanged in KOH; subhymenial hyphae densely covered by crystals. Hymenium three kinds of cystidia: (1) tapering, colorless, thin-walled, smooth, filled with refractive oil-like matter, 19.5–27 × 1.8–2.3 µm; (2) bottled, colorless, thin-walled, smooth, filled with refractive oil-like matter, 19.3–24.7 × 4.6–5.4 µm; (3) halocystidia, colorless, thin-walled, smooth, filled with refractive oil-like matter, 17–19 × 5.5–7 µm. Basidia cylindrical, with a basal clamp connection and four sterigmata, filled with refractive oil-like matter, 17–21 × 3–7 µm; basidioles numerous, in shape similar to basidia but smaller. Basidiospores ellipsoid, colorless, thin-walled, smooth, always filled with oil drop, CB –, (4.2 –) 4.6–6.4 (– 6.5) × (2.4 –) 3–3.9 (– 4) µm, L = 5.63 µm, W = 3.36 µm, Q = 1.62–1.73 (n = 60 / 2). Another specimen (paratype) examined. China • Yunnan Province, Xishuangbanna, Wild elephant Valley, GPS coordinates: 22°17'N, 100°85'E, altitude 900 m asl., on the fallen angiosperm branch, leg. C. L. Zhao, 25 January 2024, CLZhao 35703 (SWFC). Notes. The phylogenetic tree of ITS + nLSU (Fig. 3) showed that the new species Lyomyces asiaticus was clustered with L. crustosus and L. ochraceoalbus. However, morphologically, L. crustosus can be delimited from L. asiaticus by having effused basidiocarp, clavate basidia (26 × 4.5 µm) and longer ellipsoidal to subcylindrical basidiospores (5–7.5 × 2.5–3 µm; Karsten 1881). L. ochraceoalbus differs from L. asiaticus in its smooth hymenial surface, lacking a cystidium and shorter clavate basidia (11–16.5 × 3.5–5 µm; Luo et al. 2021 b). Morphologically, Lyomyces asiaticus reminds L. albopulverulentus C. L. Zhao, L. cremeus, L. denudatus Viner, L. macrosporus C. L. Zhao and L. wuliangshanensis C. L. Zhao by having the ellipsoid basidiospores. However, L. albopulverulentus can be separated from L. asiaticus by its pruinose hymenial surface and larger basidia (24.5–28.5 × 7–9 µm) and larger basidiospores (8–10.5 × 5.5–7 µm; Guan et al. 2023). L. cremeus is distinct from L. asiaticus by its smooth hymenial surface, present two types cystidia as capitate (20–40 × 3–5 µm) and tapering (18–35 × 3–4.5 µm) and thin-walled to slightly thick-walled basidiospores (Chen and Zhao 2020). In addition, L. denudatus is separated from L. asiaticus by the smooth hymenial surface, longer capitate cystidia (34.9–62 × 4–5.5 µm) and suburniform basidia (15–21.1 × 3.8–5.5 µm; Viner and Miettinen 2022). The species L. macrosporus differs from L. asiaticus due to its reticulate hymenial surface and longer basidia (22.2–38 × 4.5–7 µm) and larger basidiospores (6.7–8.9 × 4.4–5.4 µm; Chen and Zhao 2020). Moreover, L. wuliangshanensis can be delimited from L. asiaticus by its smooth to more or less tuberculate hymenial surface and two kinds of cystidia as capitate (22–37 × 3–6 µm) and tapering (21–35 × 4–6.5 µm; Chen and Zhao 2020).