Meruliopsis rhizomorpha Y. C. Dai, Chao G. Wang & Yuan Yuan 2025, sp. nov.

Meruliopsis rhizomorpha Y. C. Dai, Chao G. Wang & Yuan Yuan sp. nov. Figs 10, 11 Etymology. Rhizomorpha (Lat.): refers to the species having rose-colored rhizomorphs when fresh. Diagnosis. Differs from other Meruliopsis species by resupinate basidiomata with a white pore surface when fresh, rose-colored rhizomorphs, round to angular pores of 2–4 per mm, subicular hyphae distinctly wider than tramal hyphae, smooth hymenial cystidia, ellipsoid to broadly ellipsoid basidiospores measuring 3.8–4.2 × 2.3–2.7 µm. Type. CHINA • Hunan Province, Changsha, Yuelushan Forest Park, on fallen angiosperm branch, 18 April 2023, Dai 24733 (BJFC 042287, holotype). Description. Basidiomata annual, resupinate, soft, without odor or taste when fresh, soft when dry, up to 15 cm long, 6 cm wide, and 0.2 mm thick at the center. Pore surface white when fresh, becoming white to cream upon drying; sterile margin white when fresh and dry, up to 2 mm wide, and with rose-colored rhizomorphs when fresh; pores round to angular, 2–4 per mm; dissepiments thin to slightly thick, entire to slightly lacerate. Subiculum white, soft when dry, up to 0.1 mm thick. Tubes concolorous with pore surface, soft when dry, up to 0.1 mm long. Hyphal system monomitic; generative hyphae simple septate, hyaline, IKI -, weakly CB +; tissues unchanged in KOH. Subicular hyphae slightly thick-walled with a wide lumen, sometimes encrusted with fine crystals, frequently branched at more or less a right angle, straight to more or less flexuous, interwoven, 4–7 µm in diam. Tramal hyphae thin-walled with a wide lumen, frequently branched, straight to slightly flexuous, subparallel along the tubes, agglutinated, 2.5–3 µm in diam. Hymenial cystidia present, clavate, thin-walled, smooth, 30–46 × 5–5.5 µm; cystidioles absent. Basidia mostly clavate, sometimes constricted at middle, with four sterigmata and a simple basal septum, 16–27 × 5–6 µm; basidioles of similar shape to basidia, but smaller. Large stellate crystal agglomerations present among the tube trama. Basidiospores ellipsoid to broadly ellipsoid, hyaline, thin-walled, smooth, IKI -, CB -, (3.6 –) 3.8–4.2 (– 4.6) × (2 –) 2.3–2.7 (– 2.9) µm, L = 3.95 µm, W = 2.53 µm, Q = 1.55–1.59 (n = 90 / 3). Additional specimens examined. CHINA • Guizhou Province, Guiyang, Qianlingshan Park, fallen branch of Pinus massoniana, 21 August 2023, Dai 25816 (BJFC 043365), Dai 25742 (BJFC 043291). Notes. Meruliopsis rhizomorpha is similar and closely related to M. leptocystidiata C. C. Chen & Sheng H. Wu by the white to cream pore surface, encrusted subicular hyphae, and smooth hymenial cystidia. However, the latter has smaller pores (4–5 per mm vs. 2–4 per mm, Chen et al. 2020) and narrower basidiospores (3–4 × 1.5–2 µm vs. 3.8–4.2 × 2.3–2.7 µm, Chen et al. 2020). Meruliopsis faginea Volobuev & Ismailov also has almost the same size pores as M. rhizomorpha (3–4 per mm in M. faginea, 2–4 per mm in M. rhizomorpha, Crous et al. 2021) and long hymenial cystidia, but it differs from M. rhizomorpha by lacking rhizomorphs, having a pale grayish brown pore surface with light pinkish brown tints when fresh, a cottony to fimbriate sterile margin, and slimmer suballantoid to ellipsoid basidiospores (4–4.9 × 2–2.3 µm vs. 3.8–4.2 × 2.3–2.7 µm, Crous et al. 2021). In Wang et al. (2023), the sequences of three species, M. ambigua (Berk.) Ginns, M. bella (Berk. & M. A. Curtis) Ginns, and M. miniata (Wakef.) Ginns are unavailable. However, M. ambigua has effused-reflexed basidiomata and a dark purple to violet-brown pore surface (Ginns 1976), which differs from M. rhizomorpha. Though M. bella and M. miniata both have resupinate basidiomata and almost the same pore sizes (2–4 per mm in M. bella, 2–3 per mm in M. miniata, Ginns 1971; Ginns 1976), the rose-colored rhizomorphs are absent.