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

Figs 6 C – G, 14

Etymology.

baishanzu, for the geographic origin of the type collection.

Diagnosis.

Pluteus baishanzuensis differs from P. lauracearum by its brown glandular dots on the surface of the pileus, exceeding lamellae on the margin of the pileus, small basidiospores, and thin-walled pleurocystidia. The ITS genetic distance is 0.073 (SE = 0.014).

Holotype.

CHINA • Zhejiang Province, Baishanzu National Forest Park, 27°56'26.52"N, 119°18'79.45"E, alt. 1525 m. 2 August 2024, R. P. Liu, FJAU 66622 (Collection no.: Liu 191) (ITS: PQ 810761, LSU: PQ 810738, tef 1: PQ 811048).

Description.

Basidiomata medium-sized. Pileus 23–32 mm diam; convex or plano-convex; surface white (2.5 Y 9 / 2), central part covered with brown (5 YR 5 / 2) to light brown (2.5 Y 5 / 2) glandular dots or finely pruinose, forming dark brown (2.5 YR 5 / 2) vein-like striate, extend to the margin; smooth, hygrophanous; margin exceeding lamellae. Context white (2.5 P 9 / 2). Lamellae free, 3–7 mm wide, moderately crowded, initially white (10 P 9 / 2) to later flesh-pink (5 R 9 / 2), unequal, thicker, slightly ventricose, edges flocculose, and white or slightly pink. Stipe 36–46 × 1–3 mm, fibrous, hollow, clavate, base expanded into a bulbous, the upper part of the stipe hyaline (2.5 P 9 / 2) to white (10 P 9 / 2), transitioning downward to brown (5 YR 5 / 2) to dark brown (2.5 YR 5 / 2), the surface covered with white finely pruinose (10 P 9 / 2). Spore print pink.

Basidiospores [120 / 5 / 2] 6.0–6.5 (– 7.0) × 5.0–6.0 (– 6.5) µm, avL × avW = 6.2–6.5 × 5.3–5.6 µm, Q = 1.08–1.20 µm, avQ = 1.13–1.18 µm, subglobose to broadly ellipsoid, smooth, slightly pinkish, thin-walled. Basidia 24–31 × 8–12 μm, clavate to broadly clavate, thin-walled, 4 - sterigmate. Pleurocystidia 47–95 × 16–31 μm, rare, scattered, fusiform or broadly subfusiform, bluntly rounded apically, thin-walled, smooth, hyaline. Lamellar edge sterile. Cheilocystidia 35–66 × 12–21 μm, abundant, clustered, mostly clavate to narrowly clavate, a few subfusiform, bluntly rounded apically, thin-walled, smooth, hyaline. Pileipellis a hymeniderm, with terminal elements 66–133 × 19–25 μm, long clavate, narrowly clavate, subcylindric or subfusiform, thin-walled, with brown intracellular pigment. Stipitipellis a cutis, hyphae 4–7 μm diam, cylindrical, hyaline, thin-walled. Caulocystidia 31–53 × 15–28 μm, clustered, narrowly clavate to clavate or broadly clavate, apically obtusely rounded, with brownish intracellular pigment, smooth, thick-walled. Clamp connections absent in all tissues.

Habitat.

Solitary to scattered on decaying wood of broad-leaved trees (Quercus myrsinifolia Blume).

World distribution.

China.

China distribution.

Zhejiang Province.

Additional specimens examined.

CHINA • Zhejiang Province, Baishanzu National Forest Park, 27°76'5.02"N, 119°18'79.54"E, alt. 1535 m. 1 August 2024, R. P. Liu, FJAU 66621 (Collection no.: Liu 178) (ITS: PQ 810762, LSU: PQ 810739, tef 1: PQ 811049).

Notes.

Pluteus baishanzuensis is distinguished by its thin pileus with brownish glandular dots on the surface, moderately crowded lamellae, and distribution restricted to East Asia (China).

Morphologically, P. baishanzuensis shares similarities with P. lauracearum but can be differentiated by several key features: P. baishanzuensis possesses an unstriate pileus margin and smaller basidiospores (avL × avW = 6.2–6.5 × 5.3–5.6 µm), while P. lauracearum exhibits striate pileus margin and larger basidiospores (avL × avW = 7.3 × 6.0 µm). These taxa also differ in their geographic distribution, with P. baishanzuensis occurring in East Asia (China) and P. lauracearum in Central Asia and Europe (Turkey and Portugal) (Kaygusuz et al. 2021). This distinction is further supported by an ITS genetic distance of 0.073 (SE = 0.014) between these species.

Phylogenetically, P. baishanzuensis is closely related to P. cf. velutinus, although these taxa can be readily distinguished by both macroscopic and microscopic characters. Macroscopically, P. baishanzuensis exhibits dark brown vein-like striate on the pileus surface, whereas P. cf. velutinus has an entirely granulose-pruinose or slightly velvety pileus. Microscopically, P. baishanzuensis produces predominantly fusiform pleurocystidia with bluntly rounded apices and cheilocystidia lacking elongated necks. In contrast, P. cf. velutinus is characterized by polymorphic pleurocystidia with partly finger-like apices and cheilocystidia that are partially fusiform with longer, irregular necks (Malysheva et al. 2020; Malysheva et al. 2023). The ITS genetic distance between these taxa is 0.018 (SE = 0.006).