Meripilus niveomarginatus Y. C. Dai, Chao G. Wang & Yuan Yuan 2025, sp. nov.

Meripilus niveomarginatus Y. C. Dai, Chao G. Wang & Yuan Yuan sp. nov. Figs 20, 21 Etymology. Niveomarginatus (Lat.): refers to the species having a white sterile margin when fresh. Diagnosis. Differs from other Meripilus species by resupinate basidiomata with orange-yellow to peach when fresh, white sterile margin when fresh, angular to irregular pores of 6–8 per mm, thick-walled and apically encrusted hyphoid cystidia, broadly ellipsoid basidiospores measuring 4.2–5.2 × 4–4.6 µm. Type. CHINA • Guangdong Province, Zhaoqing, Dinghushan Nature Reserve, on rotten wood of Pinus massoniana, 28 April 2018, Dai 18540 A (BJFC 027008, holotype). Description. Basidiomata annual, resupinate, soft corky, and without odor or taste when fresh, becoming hard corky to somewhat rigid upon drying, up to 15 cm long, 6 cm wide, and 4 mm thick at center. Pore surface brownish vinaceous, orange-yellow to peach when fresh, becoming reddish brown after bruising, pinkish buff, vinaceous gray, dark brown to black when dry; sterile margin distinct, thinning out, white when fresh, cream to olivaceous buff when dry, up to 2 mm wide; pores angular to irregular, 6–8 per mm; dissepiments thin, slightly lacerate. Subiculum cream, corky, up to 1 mm thick. Tubes paler than pore surface, cinnamon buff, hard corky when dry, up to 3 mm long. Hyphal system monomitic; generative hyphae simple septate, hyaline, smooth, IKI -, CB +; tissues becoming dark brown in KOH. Subicular hyphae distinctly thick-walled with a wide lumen, rarely branched and simple septate, more or less flexuous, interwoven, 4–8 µm in diam. Tramal hyphae distinctly thick-walled with a wide lumen, occasionally branched, moderately simple septate, slightly flexuous, subparallel along the tubes, agglutinated, 4–6 µm in diam. Hyphoid cystidia present, arising from tramal hyphae and completely embedded in trama, not projecting from the hymenium, sometimes projecting from the dissepiment edge, thick-walled with swollen tips, apically encrusted, 10–15 µm in diam. at the apex. Hymenial cystidia absent; cystidioles fusoid, thin-walled, smooth, 13–14 × 4–5 µm; basidia barrel-shaped to capitate, with four sterigmata and a simple basal septum, 14–17 × 7–9 µm; basidioles of similar shape to basidia, but smaller. Basidiospores broadly ellipsoid, hyaline, thin-walled, smooth, with one medium or small guttule, IKI -, weakly CB +, (4 –) 4.2–5.2 (– 5.5) × (3.8 –) 4–4.6 (– 4.8) µm, L = 4.78 µm, W = 4.16 µm, Q = 1.13–1.17 (n = 90 / 3). Additional specimens examined. CHINA • Fujian Province, Quanzhou, Qingyuanshan, on fallen trunk of Pinus massoniana, 23 September 2017, Dai 18268 (BJFC 025793); • Hainan Province, Baisha County, Yinggeling Nature Reserve, on rotten wood of Pinus latteri, 10 June 2017, Dai 17695 (BJFC 025227); • Zhejiang Province, Wuyi County, on rotten wood of Pinus massoniana, 13 October 2023, Dai 26373 (BJFC 043923). Notes. Meripilus niveomarginatus is similar and related to M. rigidus by the resupinate and rigid basidiomata with a pinkish buff to vinaceous gray or dark brown pore surface when dry, distinctly thick-walled generative hyphae, and thick-walled and apically encrusted hyphoid cystidia. However, the latter has round and smaller pores (10–12 per mm vs. 6–8 per mm, Wang et al. 2024), relatively smaller basidiospores (4–4.6 × 3.2–4 µm vs. 4.2–5.2 × 4–4.6 µm, Wang et al. 2024), and so far, it is only known from Central and South America. Similarly, Meripilus albostygius and M. sulphureus also have rigid basidiomata and thick-walled and apically encrusted hyphoid, but M. albostygius has smaller basidiospores (4–4.7 × 3.2–4 µm vs. 4.2–5.2 × 4–4.6 µm, Wang et al. 2024) and, to date, only occurs in Central America; M. sulphureus has a sulphurous pore surface when fresh and narrower basidiospores (4–5 × 3.5–4 µm vs. 4.2–5.2 × 4–4.6 µm, Dai and Dai 2018). Meripilus roseus (Jia J. Chen & Y. C. Dai) Westph. & Rajchenb. and M. niveomarginatus share a rose or brownish vinaceous pore surface when fresh. However, the former has an almost lacking sterile margin and smaller basidiospores (3.5–4.1 × 3.1–3.8 µm vs. 4.2–5.2 × 4–4.6 µm, Chen and Dai 2021). Poria endoxantha Petch was originally described from Sri Lanka, and it is characterized by a rose-pink to salmon-pink pore surface when fresh, becoming brown or blackish brown upon bruising, thick-walled hyphoid cystidia embedded in trama, globose basidiospores of 5–7 µm in diam., and growth on angiosperm wood in the tropics (Petch 1922; Lowe 1966). Meripilus niveomarginatus is similar to Poria endoxantha in morphology, but the latter has pale yellowish-brown subicular hyphae that are obviously wider than tramal hyphae, while M. niveomarginatus has almost uniform hyphae in subiculum and trama. In addition, Poria endoxantha has bigger basidiospores (5–7 µm vs. 4.2–5.2 × 4–4.6 µm, Lowe 1966) and growth on angiosperm wood in the tropics, differing from M. niveomarginatus.