Laccaria sinolateritia Y. D. Xu & Z. M. He 2025, sp. nov.

Laccaria sinolateritia Y. D. Xu & Z. M. He sp. nov. Figs 2 g – i, 5, 6e, f Etymology. ‘ sino ’ referring to China, ‘ lateritia ’ (Latin) referring to its red to brownish orange fruiting body. Diagnosis. Laccaria sinolateritia is characterized by brownish red basidiomata, globose to subglobose echinulate basidiospores, and the presence of pileocystidia and caulocystidia. Type. China • Yunnan Province: Jingdong Yi Autonomous County, Ailaoshan, at 24.904444°N, 101.059444°E, alt. 2500 m, 8 August 2024, P. Zhang 5456 (MHHNU 11956, holotype). Description. Basidiomata small to medium-sized. Pileus 10–40 mm in diam, at first convex, then plano-concave to concave; surface tomentose, brownish red (6 B 4), subhygrophanous; translucent-striate or rugulose-sulcate, straight, undulate with age. Lamellae distant, entire, adnate, broad (about 5 mm high), ventricose, concolorous with pileus surface. Stipe 35–50 × 1–3 mm, brownish red (6 B 4), equal, broadly fistulose; surface covered with whitish (2 A 1) longitudinal fibrils; base with a whitish (2 A 1) mycelium. Context brownish (6 A 4). Basidiospores [100 / 4 / 2] (7) 7.5–10 (10.5) × (7) 7.5–10 (10.5) μm, Q = (0.90) 0.91–1.07 (1.11), Qm = 1.00 ± 0.05, mostly globose, hyaline, echinulate; spines 2–2.5 (3) μm long, ca. (1) 1.5–2 μm wide at base, crowded; hilar appendix 1.3–2.5 long, prominent, subtruncate. Basidia 40–58 × 12–14 μm, with 4 sterigmata up to 12 μm long, hyaline, subcylindrical to clavate. Pleurocystidia and cheilocystidia not seen. Lamellar trama subregular to interwoven; hyphae cylindrical, hyaline, thin-walled, 2–6 (7) μm wide. Pileipellis a cutis, hyphae cylindrical, 8–10 (12) μm in diameter with some hyphal ends, subregular to interwoven. Pileocystidia abundant, 25–45 × 5–15 μm, cylindrical to clavate, vertically to subvertically arrange, scattered to aggregating into clusters on the pileus surface. Stipitipellisa cutis, composed of cylindrical hyphae 5–10 (11.5) μm wide with abundant caulocystidia, thin- to thick-walled (≤ 0.5 μm). Caulocystidia 37.5–55 (67.5) × 7.5–9.5 (10) μm, clavate, scattered to aggregating into clusters on the stipitipellis surface. Clamp connections present in all parts of basidiomata. Ecology. Gregarious, under the trees of Fagaceae, in subtropical montane forests, summer (Aug.). Distribution. Known from the subtropical zones of China. Additional specimen examined. China • Yunnan Province: Jingdong Yi Autonomous County, Ailaoshan, at 24.904444°N, 101.059444°E, alt. 2500 m, 8 August 2024, P. Zhang 5458 (MHHNU 11958). Notes. Macroscopically, L. lateritia Malençon and L. sinolateritia are easily confused. For instance, they share similar-sized basidiomata, reddish-brown pileus and similar-sized basidiospores (7.5–10.5 × 7.5–10.5 µm in L. lateritia vs. 7.5–10 × 7.5–10 µm in L. sinolateritia). However, L. lateritia can be distinguished by the production of 2 - spored basidia, shorter spines (± 1 μm high vs. 2–2.5 μm high in L. sinolateritia) and the presence of cheilocystidia (Cooper 2015). Additionally, L. darjeelingensis resembles L. sinolateritia in its red basidiomata, but differs in having smaller basidiospores (5.9–7.6 × 5.9–7.6 µm vs. 7.5–10 × 7.5–10 µm in L. sinolateritia) and abundant flexuous pleurocystidia and cheilocystidia (Thapa et al. 2024). According to the phylogenetical analysis (Fig. 1), L. subroseoalbescens (species 68) and L. infundibuliformis (species 69) are related to L. sinolateritia (species 67), and form a clade with low support (54 % BP, 0.91 PP). Laccaria subroseoalbescens is characterized by a yellow pileus, the presence of cheilocystidia and pleurocystidia, and the absence of pileocystidia (Tang et al. 2024). Laccaria infundibuliformis differs in its smaller pileus (8–27 mm in diam vs. 10–40 mm in diam in L. sinolateritia), smaller basidia (29–50 × 6–9 µm vs. 40–58 × 12–14 μm in L. sinolateritia), and the absence of pileocystidia (Thapa et al. 2024). The four-locus phylogenetical analysis also supports the identification of the four Chinese samplesKUN-HKAS 83382, GMM 6776, T 168, and T 107 as L. sinolateritia (pairwise identity values of ITS = 99.39 % – 100 %).