Pluteus umbrosus (Pers.) P. Kumm.

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 umbrosus (Pers.) P. Kumm. , Führ. Pilzk. (Zerbst) (1871: 98)

Figs 18 D, E , 20

Description.

Basidiomata large-sized. Pileus 50–52 mm diam; convex to hemispherical, with a low, broad umbo; surface reddish-brown (7.5 YR 7 / 8), distributed with granular tan (7.5 YR 5 / 10), dense and dark brown in the center (7.5 YR 5 / 14), forming vein-like striate; margin crenulate, with small rounded or blunt teeth. Lamellae reddish-brown (2.5 R 5 / 6), free, crowded, thick, unequal, slightly ventricose, 5–7 mm wide, with brown and even to flocculose edges; lamellar edge commonly with brown pigment. Stipe 43–48 × 5–8 mm, cylindrical, gradually thickening toward the base, fibrous, surface reddish-brown with tan granules (2.5 YR 6 / 10). Odorless. Spore prints pink.

Basidiospores [200, 4, 1] 5.0–6.0 (– 7.0) × 4.5–5.0 μm, avL × avW = 5.8–6.0 × 5.3–5.6 µm, Q = 1.05–1.33 μm, avQ = 1.10–1.16 μm, subglobose to broadly ellipsoid, slightly pinkish, smooth, thin-walled. Basidia 26–30 × 6–10 μm, clavate, thin-walled, 4 - sterigmate, and hyaline. Pleurocystidia 55–90 × 22–37 μm, abundant, scattered, fusiform to lageniform, often with tapering apex, or mucronate, 5–17 μm long, thin-walled, smooth, hyaline. Lamellar edge sterile. Cheilocystidia 41–75 × 14–20 μm, numerous, clustered, subfusiform to fusiform, or ventricose, with small irregular apical horns, 4–13 μm long, thin-walled, generally with brown intracellular pigment. Pileipellis a trichohymeniderm composed of narrowed fusiform and clavate elements, with terminal elements (51 –) 62–170 (– 190) × 9–27 μm, often grouped in clusters, pointed towards the apex, with brown intracellular pigment, thin and smooth. Stipitipellis a cutis, hyphae 5–13 µm diam, cylindrical, hyaline, thin-walled. Caulocystidia 53–125 × 10–24 μm, numerous, usually in clusters, cylindrical to slightly narrowly lageniform, rounded at apex, with brown to pale brown intracellular pigment, slightly thick-walled. Clamp connections absent in all tissues.

Habitat.

Scattered on fallen wood with Sphagnum growing in broad-leaved forests.

World distribution.

Denmark, Finland, Norway, Sweden ( Heilmann-Clausen 2012), Germany ( Krieglsteiner 2003; Ludwig 2007), Britain and Ireland ( Orton 1986; Legon et al. 2005), Italy ( Boccardo et al. 2008), Switzerland ( Breitenbach and Kränzlin 1995), Netherlands ( Vellinga 1990), Spain ( Justo et al. 2011 a), Russia ( Malysheva et al. 2016), Turkey ( Kaygusuz et al. 2019), China ( Xu 2016).

China distribution.

Northeast, North, Northwest, Southwest China.

Additional specimens examined.

CHINA • Jilin Province, Changbai Mountain Old Mountain Gate ; Scattered on fallen wood with Sphagnum growing in broad-leaved forests; 6 September 2019, J. J. Hu, FJAU 66590 (Collection no.: Hu 5140) (ITS: PP 516604 , tef 1: PP 928982 ) .

Notes.

Pluteus umbrosus is characterized by a texture on the pileus and stipe that is granular like fine flour or velvety with dark brown radial fibrils, a pileus center with a generally dark veined pattern, a brown flocculose stipe, and lamellae with a distinct brown edge ( Singer 1956; Orton 1986; Vellinga 1990; Kaygusuz et al. 2019).

The general morphological characteristics are similar to those of P. umbrosoides and P. granularis . However, morphologically, P. umbrosus has a brown lamellae edge, while the mature P. umbrosoides and P. granularis do not have a pigmented lamella edge ( Kaygusuz et al. 2019). Microscopically, P. umbrosus differs from P. granularis in having a slightly wider basidiospore size of 5.8–6.0 × 5.3–5.6 μm and very long pileipellis elements reaching over 270 μm. P. umbrosus has a pleurocystidia with 1–2 horns without apical mucilage, while P. granularis has a pleurocystidia with 1–3 horns with distinctly apical mucilage. Additionally, P. umbrosus can be distinguished from P. granularis by its caulocystidia, which have a broadly rounded apex (up to 27 μm in width) ( Kaygusuz et al. 2019).

The phylogeny shows that P. umbrosus from China clustered in the same branch as P. umbrosus from Italy, Russia, and Turkey with high support (MLB = 93, BPP = 0.92, Fig. 3 ). P. umbrosus is most closely related to P. granularis , they are sister groups, and their ITS genetic distance is 0.005 (SE = 0.003), tef 1 genetic distance is 0.006 (SE = 0.003).

Figures

Figure 3. Phylogenetic tree of the / umbrosus clade and / pantherinus lineage of the sect. Hispidoderma. The best tree from the ML and BI analysis of the 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. This study species is in bold and red font.

Figure 18. Basidiomata features. A – C. Pluteus costatus (A, B. FJAU 66589, C. FJAU 66618). D, E. P. umbrosus (FJAU 66590). F – H. P. umbrosoides (FJAU 66615). I, J. P. granularis (FJAU 66612). A – C. Photos by Di-Zhe Guo. D, E. Photos by Jia-Jun Hu. C, F – H. Photos by Gu Rao. I, J. Photos by Zheng-Xiang Qi. Scale bars: 1 cm.

Figure 20. A. Macroscopic characteristics of Pluteus umbrosus. B. Basidiospores. C. Caulocystidia. D. Pleurocystidia. E. Cheilocystidia. F. Pileipellis elements. Scale bars: 1 cm (A); 10 µm (C, D, E); 20 µm (B, F).