Hyphoderma sordidum Y. Yang & C.L. Zhao
MycoBank no.: 849949.
Basidiomata Annual, resupinate, adnate, membranous, odorless and up to 5 cm long, 2.5 cm wide and 50–150 µm thick. Hymenial surface smooth, white to cream when fresh, cream upon drying. Sterile margin white, fimbriate, up to 1–2 mm wide. Hyphal system Monomitic; generative hyphae with clamp connections; colorless, thin-walled, interwoven, 1.5–2 µm in diameter; IKI–, CB–, tissues unchanged in KOH. Hymenium Cystidia tubular, basally widened, tapering but without sublate apex, slightly sinuous, colorless, thin-walled, 42–72.5 × 6–11 µm; basidia clavate to subcylindrical, constricted in the middle to somewhat sinuous, with four sterigmata and a basal clamp connection, 8–14 × 3–3.5 µm; basidioles in shape similar to basidia, but slightly smaller. Basidiospores ellipsoid, colorless, thin-walled, smooth, some with irregular oil droplets inside, IKI–, CB–, (2.5–)3–4.5 × (1.5–)2–3(–4) µm, L = 3.62 µm, W = 2.35 µm, Q = 1.56–1.70 (n = 60/2).
Additional specimens examined (paratypes)—China, Yunnan Province, Qujing, Zhanyi District, Yanzhu Village. GPS coordinates: 25°44′ N, 103°36′ E; altitude: 1950 m asl. On fallen unidentified angiosperm branches, leg. C.L. Zhao, 7 March 2023, CLZhao 17908; CLZhao 27379 (SWFC).
Notes: Hyphoderma anthracophilum (Bourdot) Jülich, H. cremeoalbum (Höhn. & Litsch.) Jülich, H. multicystidium (Hjortstam & Ryvarden) Hjortstam & Tellería, H. tropicum and H. obtusiforme J. Erikss. & Å. Strid are similar to H. sordidum by having ellipsoid basidiospores. However, H. anthracophilum differs from H. sordidum by the cracked hymenophore and larger basidiospores of 6–9 × 4–6 µm; H. cremeoalbum is distinct from H. sordidum by having larger basidia (30–45 × 7–9 µm) and larger basidiospores (10–14 × 5–6 µm) ; H. multicystidium is separated from H. sordidum by the reticulate and tomentose hymenial surface, wider generative hyphae (2–3 µm) and larger basidiospores (8–10 × 4.5–5 µm); H. obtusiforme differs in having wider generative hyphae (3–4 µm), larger basidia (30–40 × 6–8 µm) and larger basidiospores (10–12 × 5–6 µm); and H. tropicum is distinguished from H. sordidum by having tuberculate hymenial surface, moniliform cystidia and larger basidiospores (6.5–7.5 × 3–4 µm). Hyphoderma crystallinum, H. marginatum, H. membranaceum, H. moniliforme and H. tenuissimum C.L. Zhao & Q.X. Guan are similar to H. sordidum by having membranous basidiomata. However, H. crystallinum differs in H. sordidum by hymenial surface with scattered nubby crystals, larger basidia (21.5–31 × 6–8.5 µm) and larger allantoid basidiospores (11–14.5 × 4–5.5 µm); H. marginatum is separated from H. sordidum by having cracking hymenial surface, cylindrical cheilocystidia and larger basidiospores (9–10 × 3.5–4.5 µm); H. membranaceum is distinct from H. sordidum by having cracking hymenial surface, moniliform cystidia and larger basidiospores (11–13.5 × 4.5–5.5 µm); H. moniliforme differs from H. sordidum by having cracking hymenial surface, larger basidia (20–30.5 × 6–7.5 µm) and larger basidiospores (6–9 × 3–4.5 µm); and H. tenuissimum is distinguished from H. sordidum by having tuberculate to minutely grandinioid hymenial surface, larger cylindrical cystidia (50–220 × 6.5–13 µm) and larger cylindrical basidiospores (7–10.5 × 3–4.5 µm).
Fig. 1 Maximum parsimony strict consensus tree illustrating the phylogeny of three new species and related species in within Polyporales based on ITS+nLSU+mt-SSU+RPB1+RPB2 sequences. The branch is labeled with a maximum likelihood lead value greater than 70%, a reduced lead value greater than 50% and a Bayesian posterior probability greater than 0.95. The new species are in bold/green, the holotypes superscript “T”.