Marasmius lidaensis S. M. Tang & Z. L. Luo 2026, sp. nov

Marasmius lidaensis S. M. Tang & Z. L. Luo sp. nov Figs 5, 6 Chinese Name: 大理大学小皮伞 (Da Li Da Xue Xiao Pi San) Etymology. The epithet “ lidaensis ” refers to the type locality, Dali University (abbreviated as “lida”), where the holotype of this species was collected. Holotype. China • Yunnan Province, Dali Autonomous Prefecture, Dali University, elev. 2,005 m, September 1, 2020, Jun He, sj 523 (HKAS 148679). Description. Basidiomata medium-sized. Pileus 20–40 mm in diam., hemispherical when young, becoming convexo-applanate to plano-concave or concave with age, dark orange (# b 07530) at center, becoming slightly desaturated yellow (# cabc 88) with margin, umbonate of center; aspects exceeding lamellae of margin; distinct, straight, and smooth on the surface; context 1–2 mm thin, tough. Lamellae 2–4 mm in diam., arcuate when young, ventricose with age, white (# ffffff); attachment emarginate; lamella edge even or entire. Stipe 30–60 × 1–3 mm, cylindrical, white (# ffffff) on the upwards, becoming dark orange (# 724620) with downward, hollow; context soft and tough surface, white (# ffffff) to pale cream; abundant floccose on the surface and mycelium grown at the base. Taste not distinctive. Basidiospores (5.2 –) 5.6–10.2 (– 11.5) × (4.2 –) 4.5–6.3 (– 5.8) μm, av. 8.6 ± 1.03 × 5.5 ± 0.48, Q = 1.1–1.7 μm, ellipsoid, smooth, hyaline, thin-walled. Basidia 35–42 × 5–7 μm, av. 38.7 ± 4.5 × 5.8 ± 1.32 μm, clavate, with a clamp connection, 4 – spored, sterigmata 1–3 μm. Basidioles 25–52 × 4–6 μm, av. 31 ± 5.2 × 5.2 ± 1.42 μm, scattered, cylindrical, clavate. Cheilocystidia 24–47 × 4–7 μm, av. 30.5 ± 4.6 × 6.1 ± 0.8 μm, mostly clavate, flexuose, rarely branched, thin-walled. Pleurocystidia 21–41 × 4–7 μm, av. 31.3 ± 4.1 × 5.7 ± 0.7 μm, abundant, clavate, flexuose, thin-walled. Lamellae trama hyphae cylindrical or swelling, 4–8 μm in diam., av. 5.9 ± 1.6 μm, thin-walled, with a clamp connection, hyaline in 5 % KOH solution. Stipitipellis a cutis of cylindrical, parallel, thin walled, hyaline in 5 % KOH solution, 19–90 × 3–5 μm, av. 50.9 ± 23.7 × 4.0 ± 0.6 μm, present connection camp. Pileipellis a hymeniderm composed of cells, swelling, 7–17 × 4–11 μm, av. 14.8 ± 3.6 × 8.8 ± 2.0 μm, parallel, hyaline in 5 % KOH solution, with a clamp connection. Habitat and distribution. Solitary in mixed forest dominated by Pinus sp. and various broadleaved trees, sometimes basidiomata occur on grass. Only known from the Yunnan Province of Dali Autonomous Prefecture. GenBank accession numbers. ITS: HKAS 148679, PX 353111; HKAS 148680, PX 353112; LSU: HKAS 148679, PV 802690; HKAS 148680, PV 802691. Additional materials examined. China • Yunnan Province, Dali Autonomous Prefecture, Dali University, elev. 2,007 m, July 8, 2021, Jun He, sj 525 (HKAS 148680); June 6, 2024, Song-Ming Tang, 2024060601. Notes. Marasmius lidaensis is distinguished from other Marasmius species by its clearly striated pileus surface, dark orange at the center, becoming slightly desaturated yellow with a margin; the stipe is white on the upper side, becoming dark orange on the lower side, with a soft and rigid context surface, and is abundant with floccose hairs on the surface. According to our multi-locus phylogenetic analyses, M. lidaensis was clustered together with M. maximus Hongo (BRNM 714571) and M. brunneospermus Har. Takah. (BRNM 714669). However, M. maximus has an ochre-brown to pale brownish to pale ochraceous pileus, and slightly broadened at stipe base, pleurocystidia absent, and irregular lobate cheilocystidia (Hongo 1962); and the ITS base difference between the specimen M. maximus (BRNM 714571) and M. lidaensis (HKAS 148679, holotype) is 1.3 % (10 / 778). Marasmius brunneospermus has a brown to brownish orange pileus, and smaller basidia (35–42 × 5–7 μm vs. 23–27 × 3.3–4.6 μm) (Takahashi 1999); and the ITS base difference between the specimen M. brunneospermus (BRNM 714571) and M. lidaensis (HKAS 148679, holotype) is 8.7 % (68 / 778).