Pluteus albivillus Z. X. QI, B. Zhang & Y. Li, 2025

Qi, Zheng-Xiang, Wang, Li-Bo, Qian, Ke-Qing, Shi, Li-Li, Hu, Jia-Jun, Tuo, Yong-Lan, Rao, Gu, Samwel Jacob, Muharagi, Liu, Rui-Peng, Liu, Ming-Hao, Guo, Di-Zhe, Liu, Ya-Jie, Zhang, Bo, Li, Xiao & Li, Yu, 2025, Integrating morphology, phylogeny, substrate, and distribution: clarifying the major phylogenetic framework of Pluteus sect. Hispidoderma (Agaricales, Pluteaceae) and describing 18 species, IMA Fungus 16, pp. e 154329-e 154329 : e154329-

Pluteus albivillus Z. X. QI, B. Zhang & Y. Li sp. nov.

Figs 6 A, B , 15

Etymology.

Derived from Latin ‘ albus’ (white) and ‘ villus’ (downy), referring to the white downy hairs on the pileus surface.

Diagnosis.

Pluteus albivillus differs from P. velutinus by its pileus surface with white villi, flocculose lamellae edges, fibrous stipe, and two forms of pleurocystidia (fusiform and narrowly clavate to clavate). The ITS genetic distance is 0.058 (SE = 0.010), tef 1 genetic distance is 0.106 (SE = 0.031).

Holotype.

CHINA • Xinjiang Uygur Autonomous Region, Altay Kanas National Forest Park . 48°41'26.33"N, 87°02'33.09"E, alt. 1287 m. Scattered on decaying wood of Xinjiang larch ( L. sibirica ). 21 August 2022, Z. X. Qi, FJAU 66613 (Collection no.: Qi 1117) (ITS: PQ 810759 , LSU: PQ 810736 , tef 1: PQ 811046 ).

Description.

Basidiomata medium-sized. Pileus 24–29 mm diam; hemispherical when young, brown (10 R 5 / 2); expanding to convex, moderate reddish brown (10 R 5 / 2) to weak reddish brown (2.5 R 5 / 2); surface covered with fine villous covering when dry, hygrophanous when damp, smooth, margin inflexed. Lamellae free, 3–5 mm wide, crowded, initially white (10 P 9 / 2) to later pink (5 R 9 / 2), unequal, thicker, with flocculose edges; lamellar edge concolorous to the sides. Stipe 30–35 × 3–5 mm, clavate, slightly expanded at the base, fibrous, surface with longitudinal striate, hyaline to white (10 P 9 / 2) in the upper part, transitioning downward to brown (10 R 5 / 2) to dark brown (2.5 R 5 / 2). Spore print unknown.

Basidiospores [90 / 3 / 1] (– 6.5) 7.0–8.0 (– 8.5) × 5.5–6.5 (– 7.0) µm, avL × avW = 7.3–7.6 × 5.8–6.0 µm, Q = 1.07–1.34 µm, avQ = 1.20–1.25 µm, subglobose, broadly ellipsoid to ellipsoid, smooth, slightly pinkish, thin-walled. Basidia 26–32 × 7–10 μm, clavate, thin-walled, 4 - sterigmate, hyaline. Pleurocystidia 49–86 × 20–36 μm, few, scattered, two forms, one narrowly clavate to clavate, bluntly rounded apically, the other long fusiform, pointed apically, thin-walled, smooth, hyaline. Lamellar edge sterile. Cheilocystidia 35–66 × 12–21 μm, abundant, clustered, clavate, pyriform to narrowly clavate, smooth, thin-walled, hyaline. Pileipellis a hymeniderm formed of variable and often mixed elements, from short and rounded to clavate, subfusiform or cylindrical terminal elements, 57–130 × 15–36 μm, with pale brown intracellular pigment, thin-walled. Stipitipellis a cutis, hyphae 3–6 μm diam, cylindrical, hyaline, thin-walled. Caulocystidia 33–67 × 11–20 μm, clustered, narrowly clavate to clavate, apically obtusely rounded, smooth, thin-walled, hyaline. Clamp connections absent in all tissues.

Habitat.

Scattered on decaying wood of Xinjiang larch ( L. sibirica ).

World distribution.

China.

China distribution.

Xinjiang Uygur Autonomous Region.

Notes.

Pluteus albivillus is primarily characterized by fine white villi on the pileus surface (which appear smooth when wet), flocculose lamellae edges, dimorphic pleurocystidia (one form narrowly clavate to clavate, the other long-fusiform), and ecological association with decaying Larix sibirica wood.

Morphologically, P. albivillus shares similarities with P. velutinus , both producing basidiomata and basidiospores of comparable dimensions ( Malysheva et al. 2016; Ferisin and Dovana 2018). However, these taxa can be distinguished by both macroscopic and microscopic features. Macroscopically, P. albivillus exhibits flocculose lamellae edges and a harder, more fibrous stipe, whereas P. velutinus has flush lamellae edges and a brittle, bony stipe. Microscopically, P. albivillus produces dimorphic pleurocystidia (narrowly clavate to clavate and fusiform) lacking apical projections, and narrowly clavate cheilocystidia. In contrast, P. velutinus forms uniformly fusiform pleurocystidia, some bearing 1–2 unequal apical projections, and lageniform to narrowly utriform cheilocystidia with elongated necks ( Malysheva et al. 2016; Ferisin and Dovana 2018).

P. albivillus might also be confused with P. punctipes due to the brownish pileus tones and minute fibrous scales on the surface of both species. These taxa can be distinguished primarily by pleurocystidia dimensions, with P. albivillus producing shorter elements (≤ 86 µm) compared to the longer pleurocystidia (≤ 100 µm) of P. punctipes ( Orton 1960) .

Phylogenetically, P. albivillus forms a distinct, well-supported branch (MLB = 97, BPP = 0.99, Fig. 1 ), paraphyletic with P. baishanzuensis . P. albivillus is distinguished from P. baishanzuensis by its pileus with fine white villi, larger basidiospores (avL × avW = 7.3–7.6 × 5.8–6.0 µm), and preference for gymnosperm substrates in northwestern China (Xinjiang). In contrast, P. baishanzuensis exhibits a pileus with brown glandular dots, smaller basidiospores (avL × avW = 6.2–6.5 × 5.3–5.6 µm), and a preference for angiosperm substrates in southeastern China (Zhejiang). These distinctions are further supported by genetic distances of 0.037 (SE = 0.008) for ITS and 0.105 (SE = 0.017) for tef 1.

Figures

Figure 1. Phylogenetic tree of the sect. Hispidoderma of the genus Pluteus. The best tree from the ML and BI analysis of the LSU + ITS + tef 1 dataset. The two values of internal nodes respectively represent the Maximum Likelihood bootstrap (MLBP) / Bayesian posterior probability (BIPP). Nodes with a bootstrap probability (BP) ≥ 80 and a Bayesian posterior probability (PP) ≥ 0.80 are indicated in the phylogram.

Figure 6. Basidiomata features. A, B. Pluteus albivillus (FJAU 66613). C – G. P. baishanzuensis (C, D. FJAU 66621, E – G. FJAU 66622). H – J. P. velutinus (H. FJAU 66619, I, J. FJAU 66620). K, L. P. longistriatus (FJAU 66596). A, B, K, L. Photos by Zheng-Xiang Qi. C – G. Photos by Rui-Peng Liu. H – J. Photos by Gu Rao. Scale bars: 1 cm.

Figure 15. A. Macroscopic characteristics of Pluteus albivillus. B. Cheilocystidia. C. Basidiospores. D. Pleurocystidia. E. Basidia and Pleurocystidia. F. Caulocystidia. G. Pileipellis elements. Scale bars: 1 cm (A); 5 µm (C); 10 µm (B, D – F); 20 µm (G).