Pluteus variabilicolor Babos, Annls Hist. – Nat. Mus. Natn. Hung. (1978: 93)

Figs 26 A – L, 30

Description.

Basidiomata small to medium-sized. Pileus 21–42 mm diam; campanulate to hemispherical when young, egg-yellow (5.0 Y 9 / 12); gradually plano-convex at maturity, bright yellow (5.0 Y 9 / 18), brown in the middle (7.5 YR 7 / 18); the white margin, with striate from the middle to the margin, straight. Context yellowish (2.5 Y 8 / 18), odorless, 2–4 mm thick. Lamellae initially white, becoming pink to flesh-pink at maturity (2.5 Y 9 / 12–2.5 Y 8 / 12), free, crowded, thick, unequal, 3–5 mm wide. Stipe 37–75 × 6–11 mm, cylindrical to compressed, hollow, white, fibrous, base light brown (2.5 Y 8 / 16), slightly thick to bulbous, surface relatively smooth. Odorless. Spore prints pink.

Basidiospores [200, 12, 7] 5.0–5.5 (– 6.0) × 4.5–5.0 (– 5.5) μm, avL × avW = 5.2–5.5 × 4.8–5.0 µm, Q = 1.00–1.33 μm, avQ = 1.10–1.15 μm, spherical to subglobose, slightly pinkish, smooth, thin-walled. Basidia 24–30 × 7–10 μm, clavate, thin-walled, 4 - sterigmate, hyaline. Pleurocystidia 55–87 × 12–24 μm, scattered, fusiform, lageniform, or utriform, some with or without 1–2 digitiform excrescences at apex, thin-walled, smooth, hyaline. Lamellar edge sterile. Cheilocystidia 31–68 × 9–16 μm, numerous, clustered, subfusiform to fusiform, apically diverticulate or shortly rostrate, thin-walled, hyaline. Pileipellis a hymeniderm formed of variable and often mixed elements, from short and rounded to clavate or cylindrical terminal elements, 62–101 × 22–36 μm, with yellow intracellular pigment, with thin and smooth walls. Stipitipellis a cutis, hyphae 5–12 µm diam, cylindrical, hyaline, thin-walled. Caulocystidia 53–88 × 11–22 μm, mostly grouped, fusiform, lageniform to broadly lageniform, apical with short rostrate, thin-walled, smooth, hyaline. Clamp connections absent in all tissues.

Habitat.

Solitary to scattered on rotting wood in broad-leaved or mixed forests.

World distribution.

Hungary (Babos 1978), Europe from Austria (Lohmeyer et al. 1994), Italy (Lanconelli et al. 1998; Migliozzi 2011; Lezzi et al. 2014), Romania (Béres 2012), Russia (as P. castri) (Justo et al. 2011 a), Slovenia (Jogan et al. 2012), Moldova (Lezzi et al. 2014), Japan (as P. castri) (Justo et al. 2011 a), Germany (Ludwig 2007), Turkey (Kaygusuz et al. 2019), China (as P. luteus) (Ševčíková and Dima 2021).

China distribution.

Henan Province, Sichuan Province, Jiangsu Province.

Additional specimens examined.

CHINA • Henan Province, Uyang Minzhuang Forestry; 32°52'44.77"N, 113°36'34.87"E; Scattered in mixed forests dominated by Quercus serrata; 25 July 2023, Y. J. Liu, FJAU 66583 (Collection no.: Liu 797) (ITS: PP 516613, LSU: PP 516663, tef 1: PP 551599). CHINA • Henan Province, Uyang County Yihezhai Forest Area; 32°52'42.46"N, 113°36'54.17"E; Scattered on dead wood stumps in Sargasso pine forests (Pinus massoniana); 1 August 2023, Y. J. Liu, FJAU 66584 (Collection no.: Liu 858) (ITS: PP 516614, LSU: PP 516664, tef 1: PP 551600). CHINA • Henan Province, Uyang Minzhuang Forestry; 32°52'84.97"N, 113°36'39.77"E; Scattered on dead wood stumps in Sargasso pine forests (P. massoniana); 2 August 2023, Y. J. Liu, FJAU 66585 (Collection no.: Liu 881) (ITS: PP 516615, LSU: PP 516665, tef 1: PP 551601). CHINA • Henan Province, Uyang Minzhuang Forestry; 32°52'89.37"N, 113°36'38.27"E; Scattered on dead wood stumps in Sargasso pine forests (P. massoniana); 2 August 2023, Y. J. Liu, FJAU 66586 (Collection no.: Liu 889) (ITS: PP 516616, LSU: PP 516666, tef 1: PP 551602). CHINA • Henan Province, Uyang County Tongshan Lake Forest National Park; 32°52'79.87"N, 113°36'58.37"E; Scattered on dead wood stumps in Sargasso pine forests (P. massoniana); 12 August 2023, Y. J. Liu, FJAU 66587 (Collection no.: Liu 982) (ITS: PP 516617, LSU: PP 516667, tef 1: PP 551603). CHINA • Sichuan Province, Tongjiang County, Chenhe Township; 32°12'24.57"N, 107°12'53.83"E; 2 August 2023, L. B. Wang, FJAU 66588 (Collection no.: Wang 1106) (ITS: PP 516618, LSU: PP 516668, tef 1: PP 551604). CHINA • Sichuan Province, Tongjiang County, Chenhe Township; 32°12'24.55"N, 107°12'53.25"E; 2 August 2024, L. B. Wang, FJAU 66623 (Collection no.: Wang 1674) (ITS: PQ 810763, LSU: PQ 810740, tef 1: PQ 811063).

Notes.

Pluteus variabilicolor is characterized by the lively yellowish color of the pileus, the dark velvety stipe when young, the presence of caulocystidia and a pileipellis variable elements (Babos 1978; Kaygusuz et al. 2019).

Macroscopically, P. variabilicolor is very similar to P. leoninus, but the two taxa are distinguished by the structure of the pileipellis and the presence or absence of caulocystidia. The pileipellis structure of P. variabilicolor is hymeniderm, consisting of elongated cylindrical hyphae and rounded terminal elements that are clavate in shape, whereas the pileipellis structure of P. leoninus is trichohymeniderm, consisting of uniformly narrow fusiform elements. In addition, P. variabilicolor has caulocystidia, whereas P. leoninus does not (Takehashi and Kasuya 2007; Kaygusuz et al. 2019). Similarly, the pileus of both P. variabilicolor and P. chrysaegis was yellow or yellowish with veined surfaces, and the general structure of the pileipellis and the presence of caulocystidia were both observed (Pradeep et al. 2012; Lezzi et al. 2014; Kaygusuz et al. 2019). However, we can distinguish between the two by the presence of cheilocystidia, which are mucronate and thin-walled in P. variabilicolor, and non-mucronate and slightly thick-walled in P. chrysaegis (Babos 1978; Pradeep et al. 2012; Lezzi et al. 2014; Hosen et al. 2018; Kaygusuz et al. 2019).

The phylogenetic tree results based on the ITS + tef 1 dataset were consistent with the morphological results. Specimens from China in P. variabilicolor clustered in the same branch as Japan, Russia, Turkey, China and Hungary with high support (MLB = 100, BPP = 1, Fig. 4).