Leucoinocybe haizhuensis Ming Zhang, C. X. Fan & W. X. Xia 2026, sp. nov.

Leucoinocybe haizhuensis Ming Zhang, C. X. Fan & W. X. Xia sp. nov. Figs 6, 7, 8 Chinese name: 海珠白丝盖伞 Diagnosis. Leucoinocybe haizhuensis is characterized by its very small basidiomata, brown to yellowish white pileus with finely pubescent on the surface, diverse shaped cheilocystidia, 2 - spored basidia, elliptical to broadly elliptical and amyloid basidiospores (7–9 × 5–7 µm). Holotype. China • Guangdong Province: Guangzhou City, Haizhu National Wetland Park, elev. ca. 4 m, at 23°3'35"N, 113°20'30"E, 7 August 2025, Ruihua Sun and Xinyue Yang (GDGM 102360, holotype!). Etymology. The specific epithet “ haizhuensis ” refers to the type locality of this new taxon, the Haizhu Wetland Park in Guangdong Province of China. Description. Basidiomata small, mycenoid. Pileus 3–8 mm broad, paraboloid, hemispherical to convex, slightly umbonate at center, surface dry, pruinose, chocolate brown, teak brown, burnt umber (6 F 6–8), brown (6 E 4–6), yellowish brown (6 D 5–8), light orange to pale orange (6 B 3–5) when young; usually light orange to pale orange (6 B 3–5) at center, pale orange, orange white to white (5 A 1–3) toward margin when aged; margin straight, undulate, with light yellow (3 A 4, 4 A 4) to pale yellow (3 A 3, 4 A 3) striations. Lamellae adnexed, subdistant to distant, even at edge, white (2 A 2) to cream, often with 1–3 unequal lamellulae between two entire lamellae. Stipe 2–25 × 0.3–0.6 mm, central, hollow, subcylindrical, translucent, fragile, chocolate brown, teak brown, burnt umber (6 F 6–8) to brown (6 E 4–6) when young, white (1 A 1) when aged, sometimes with brown (6 E 4–6) to light orange (5 B 3–4), obviously light orange (5 B 3–4) at the base, changing to negro to brownish gray (6 F 2–3) at age, densely pruinose; basal mycelium white. Odor and taste not recorded. Basidiospores [50 / 3 / 3] 7–9 × (5) 5.5–7 μm, L m = 8.23 ± 0.58 µm, W m = 6.24 ± 0.42 µm, Q = (1.15) 1.17–1.42 (1.45), Q m = 1.32 ± 0.07, broadly elliptical to elliptical, thin-walled, smooth, hyaline in 5 % KOH, guttulate, amyloid. Basidia (18.5) 19–35 (36.5) × 5.5–7.5 (8) μm, clavate, thin-walled, yellowish white to hyaline, 2 - spored, with sterigmata 2–7.5 µm long, sometimes with a white patch, clampless. Cheilocystidia 26–44 × 6.5–13.5 µm, distinct, ovoid, conical, broadly conical, fusiform, broadly fusiform to subcapitate, sometimes apex acuminate to acute, rarely rostrate, thin-walled, hyaline, clampless. Pleurocystidia absent. Lamellar trama regular to subregular, hyaline hyphae 12–27.5 μm wide, thin-walled, clamped. Pileipellis a cutis, composed of fusiform, irregular or subcylindrical hyphae 3–12 μm wide, smooth, thin-walled, yellow to yellowish brown, clamped; pileocystidia 22–50 × 6.5–21.5 μm, ellipsoid, obovoid, clavate, broadly clavate to utriform, thin-walled to slightly thick-walled, yellowish white to hyaline, clampless. Stipitipellis a cutis, 3.5–11 μm wide, occasionally upturned, smooth, thin-walled, hyaline, clamped; caulocystidia 15–147 × 3–8.5 μm, obovoid, clavate, broadly clavate to lanceolate, thin-walled to slightly thick-walled, hyaline, clampless. Habit and distribution. Scattered or gregarious, living on Mangifera trees in broad-leaved forests. Currently only known from the type locality in southwestern China. Additional specimen examined. China • Guangdong Province: Guangzhou City, Haizhu National Wetland Park, elev. ca. - 2 m, at 23°4'39"N, 113°20'4"E, 29 April 2024, Ruihua Sun and Guorui Zhong (GDGM 94606); • Same location, elev. ca. 7 m, at 23°3'56"N, 113°20'30"E, 22 August 2024, Ruihua Sun and Liuying An (GDGM 95340); • Same location, elev. ca. 7 m, at 23°9'9"N, 113°17'21"E, 19 June 2025, Ruihua Sun and Guorui Zhong (GDGM 99242); • Same location, elev. ca. 10 m, at 23°4'48"N, 113°18'12"E, 19 June 2025, Ruihua Sun and Xinyue Yang (GDGM 99420). Notes. Morphologically, L. lenta is similar to L. haizhuensis. However, L. lenta can be distinguished from L. haizhuensis by its mostly 4 - spored basidia, smaller basidiospores (5.5–8 × 4–5.5 µm), thick-walled and larger pileocystidia (32–140 × 6–11 µm) and caulocystidia (50–150 × 6–16 µm) (Antonín et al. 2019; Kaygusuz et al. 2020; Na et al. 2024). The basidioma color of L. haizhuensis is also similar to L. auricoma. However, L. auricoma differs by its larger basidiomata (pileus up to 25 mm broad), covered with orange to yellowish orange flocci on pileus surface and smaller basidiospores (5–7 × 3–4 µm) (Takahashi 1999). In nrITS-LSU phylogenetic tree (Fig. 1), L. haizhuensis is closely related to L. taniae, both species have convex pileus, variably shaped cystidia, and similar-sized basidiospores. However, L. taniae, originally described from Spain, is different from L. haizhuensis in having larger basidiomata (pileus up to 15 mm broad), orange to reddish brown pileus, creamy or isabelline lamellae, brown to light orange stipe, 4 - spored basidia (Vila 2002; Antonín et al. 2019). In nrITS phylogenetic tree (Fig. 2), this new species is placed within Leucoinocybe clade, forming a relatively independent clade, and is closely related to L. danxiashanensis and L. papillata. However, L. danxiashanensis is distinguished from L. haizhuensis in having larger basidiomata (pileus 7–22 mm broad), light brown to brownish orange pileus, sinuate to free lamellae, narrower basidiospores (6.5–8.5 × 4.5–6.0 µm), and mostly 4 - spored basidia; L. papillata, originally described from Pakistan, is different from L. haizhuensis in having larger basidiomata (pileus up to 16 mm broad), campanulate with a distinct papilla, mustard brown to turning light brown pileus, sinuate lamellae, smaller basidiospores (4.8–7.4 × 3.9–5.8 µm) and absent cystidia (Cazabonne et al. 2025). Besides, L. danxiashanensis and L. papillata also differ in growing on forest soil, the ecological characteristic that clearly distinguishes them from L. haizhuensis.