Micropsalliota bispora J. Q. Yan, S. N. Wang, & H. Zeng sp. nov.

Fig. 2

Etymology.

Name refers to the majority of basidia are 2 - spored.

Diagnosis.

Micropsalliota bispora is mainly characterized by very small basidiomata; white to cream pileus, with the center being fawn to dull red; cymbiform basidiospores in profile view, 8.0–9.0 (9.5) × 4.0–5.0 (5.3) μm; and tibiiform cheilocystidia. It differs from M. albofelina by having bigger spores, which are up to 9.0 μm in length.

Holotype.

China • Fujian Province, Wuyishan National Park, 11 July 2022, Jun-Qing Yan, Cheng-Feng Nie, HFJAU 4253.

Description.

Pileus 3.0–5.0 mm in diameter, white to cream, fawn (7 E 4) to dull red (8 C 3) at center, plano-convex to plane, surface dry, covered with white well-developed fibrils at early age, gradually disappears with aging. Context less than 0.8 mm thick. Lamellae 0.5–1.0 mm broad, free to short adnexed, distant, white, becoming brownish orange to light brown (7 C 4–7 D 4) as mature, edge white, smooth to serrate, with two series of lamellulae. Stipe 10–25 mm long, 0.5–1.0 mm thick, cylindrical, slender, white, surface with white fibrils, gradually disappears with aging. Annulus unobserved.

Basidiospores 8.0–9.0 (9.5) × 4.0–5.0 (5.3) μm, Q = (1.6) 1.7–2.0, cymbiform in profile view, ellipsoid to elongated-ellipsoid in face view, light brown, wall 0.5 μm thick, apically thickened endosporium, without germ pore, inamyloid. Basidia 11–15 × 6.5–8.0 μm, clavate, hyaline, 2 - spored, rarely 4 - spored. Pleurocystidia absent. Cheilocystidia 35–55 × 6.8–15 (17) μm, tibiiform, apex capitate, rarely subacute, 4.0–6.0 (7.0) μm in diameter. Fibrils at the center of pileus composed of hyphae, 8.0–15 μm broad, with pale brown membranous pigment, constricted at the septa on some hyphae.

Habit and habitat.

Scattered on soil in broad-leaved forest or mixed coniferous and broad-leaved forests.

Additional specimens examined.

China • Fujian Province, Wuyishan National Park, 25 June 2022, Jun-Qing Yan, Bin-Rong Ke, HFJAU 3833.

Note.

Macroscopically, M. bispora is very similar to M. albofelina D. D. Ivanova & O. V. Morozova, with both species having very small basidiomata and well-developed scales or fibrils at an early age. However, the latter has spores that are shorter than 7.5 μm and a white center on the pileus (Crous et al. 2021). Micropsalliota longicystis T. Gao & Z. W. Ge and M. pseudoarginea Heinem. are also similar to M. bispora macroscopically, but M. longicystis has pleurocystidia and its spores shorter than 6.0 μm (Gao et al. 2024), and M. pseudoarginea has broadly clavate or ventricose-clavate cheilocystidia and its spores shorter than 5.0 μm (Zhao et al. 2010). Among the known species of Micropsalliota with a pileus generally less than 10 mm, there are no species like M. bispora with spores longer than 8.0 μm. Based solely on this characteristic, M. bispora can be distinctly differentiated from known species of Micropsalliota.

M. geesterani (Bas & Heinem.) R. L. Zhao & L. A. Parra, M. gigaspora T. Gao & Z. W. Ge, and M. ventricocystidiata Al-Sadi & S. Hussain are similar to M. bispora, with spores up to 9.0 μm, but their pilei are larger than 20 mm. Additionally, M. geesterani has a purple pileus, and fusiform, cylindrical, or narrowly clavate cheilocystidia (Parra et al. 2016), M. gigaspora has clavate cheilocystidia (Gao et al. 2024), and M. ventricocystidiata has ventricose cheilocystidia (Al-Kharousi et al. 2022).