Pseudohydnum motuoense L. Lei & Q. Zhao, 2025

Lei, Lei, Luangharn, Thatsanee, Yu, Feng-Ming & Zhao, Qi, 2025, Two new species of Pseudohydnum (Auriculariales, Basidiomycota) from the Qinghai-Tibet Plateau in China, Phytotaxa 690 (2), pp. 243-254 : 248

Pseudohydnum motuoense L. Lei & Q. Zhao , sp. nov. ( Figs. 2 , 3 )

Index Fungorum number: IF903030; Facesoffungi number: FoF 16967

Etymology:—The epithet “ motuoense ” refers to the location “Motuo, China ” from where the holotype specimen was collected.

Diagnosis:— Pseudohydnum motuoense is morphologically very similar to P. meridianum , however, the former has a longer and thicker stipe that is often expanded at the base.

Holotype:— CHINA, Xizang, Linzhi, Motuo , 29.32675317°N, 95.35616065°E, alt. 1,705 m, 10 Jul. 2022, coll. Lei Lei, LEI-477 ( KUN-HKAS 134347 )

Basidiomata small to medium-sized, tapering upwards when young. Pileus 20–55 mm diam, gradually unfolds after maturity, irregular shell-shaped to kidney-shaped; surface velutinous or mastoid, reddish brown (8 E 6) to dark brown (8 F 8) when fresh and dark brown (8 F 8) to black when dried, gelatinous when fresh, brittle when dried. Spines up to 2−5 mm long, 3−4 per mm at the base, conical, white when fresh, and white with pale green (29 A 4) tinges when dried. Context 4–6 mm thick, translucent, unchanging colour when injured, resilient. Stipe 30–60 × 6–20 mm, lateral, gelatinous, translucent, velutinate, cylindrical, sometimes laterally compressed, often expanding at the base and sometimes expanding towards the apex, surface concolourous to pileus surface or paler.

Basidiospores (5.0–) 5.5–6.8 (–7.5) × (4.0–) 4.6–6.0 (–6.5) μm, L m = 6.1 μm, W m = 5.3 μm, Q = 1.06–1.22 (n = 100/5/5), Q m = 1.21 ± 0.08, broadly ellipsoid to subglobose, hyaline, thin-walled, with a big guttule. Probasidia 8.0−10.0 × 10.5−14.0 μm, fusiform to lageniform. Hyphidia 1.5−2.5 μm wide, occasionally branched. Basidia 8.0−10.7 × 9.4−15.0 μm, four-celled, barrel-shaped, globose to subglobose, with guttules; sterigmata up to 10.5 × 2−3 μm. Contextual hyphae 1.5−4.0 μm wide, frequently branched, interwoven, thin- to slightly thick-walled, hyaline. Tramal hyphae 2.0−6.0 μm wide, frequently branched, interwoven, thin-walled, hyaline. Pileipellis is composed of subparallel or ascending hyphae, 2.0–8.0 μm wide, slightly inflated, thin- or slightly thick-walled, hyaline. Clamps are common in all parts of basidiomata.

Habitat:—Gregarious, growing on rotten wood in mixed forest with trees of Elaeocarpus , Exbucklandia , and Myrsine .

Additional material examined:— CHINA, Xizang, Linzhi, Motuo , 29.32675317°N, 95.35616065°E, alt. 1,705 m, 10 Jul. 2022, coll. Lei Lei, LEI-479 ( KUN-HKAS 134348 ) ; coll. Shu-Xin Bao, Bao 190 ( KUN-HKAS 134351 ) ; coll. Li-Heng Mu, mu320 ( KUN-HKAS 134349 ) ; coll. Feng-Ming Yu, FM22-196 ( KUN-HKAS 134350 ) .

Notes:— Pseudohydnum motuoense is characterized by small to medium-sized basidiomata, shell- to kidney-shaped pileus with reddish brown to dark brown surface, stipe often expanding at the base, and broadly ellipsoid to subglobose basidiospores. It is very similar to P. meridianum in micro-morphological characteristics, such as basidiospores size, the wide pileipellis hyphae, and sterigmata. However, the latter has a shorter and thinner stipe (20 × 5 mm) that gradually tapes to the base ( Spirin et al. 2023). Pseudohydnum motuoense shares similar morphological characteristics with P. brunneiceps but is distinguished by having shorter basidiospores (5.5–6.8 vs. 6.0–8.0 μm, Chen et al. 2020). In addition, P. motuoense grows on decaying wood in broad-leaved forests, while P. brunneiceps grows on decaying gymnosperm wood dominated by Cryptomeria japonica ( Chen et al. 2020) . Pseudohydnum motuoense exhibits characteristics similar to P. brunneovelutinum such as a dark brown and velutinous pileus and broadly ellipsoid to subglobose basidiospores. Pseudohydnum brunneovelutinum was originally described in Brazil. This species has shorter stipe (up to 15 mm), narrower hyphae on the pileal surface (2.5–5 μm), and spine tramal hyphae (1.5–2.8 μm, Coelho-Nascimento et al. 2024). Additionally, P. umbrosum , a species that also has a toned pileus surface from Asia, but differs in several key features. It has a very short or absent stipe and larger basidia (12.2–15.8 × 9.1–12.2 μm) and basidiospores (7.6–9.8 × 6.0–7.1 μm) compared to P. motuoense ( Spirin et al. 2023) . Phylogenetically, the newly identified taxon, P. motuoense , forms a well-supported clade ( MLBP = 94, BIPP = 1.00) and is categorized as a successive sister clade to both P. meridianum and P. brunneiceps ( Fig. 1 ).

Figures

FIGURE 1. Maximum likelihood tree based on the combined LSU and ITS dataset, showing the phylogenetic position of Pseudohydnum spp. Bootstrap proportions (MLBP) equal to or above 70%, and equal to or above 0.90 proportions (BIPP) are shown above the branches of the phylogenetic tree. The newly generated sequences and type specimens are shown in red or bold, respectively.

FIGURE 2. Basidiomata of Pseudohydnum. a−c P. motuoense (a. KUN-HKAS 134349; b KUN-HKAS 134347, holotype; c KUN-HKAS 134348); d−f P. purum (d KUN-HKAS 134352, holotype; e, f KUN-HKAS 134353). Bars: = 1 cm.

FIGURE 3. Microscopic features of Pseudohydnum motuoense (KUN-HKAS 134347 holotype). a basidiospores, showing germination by repetition; b basidia, hyphidia; c hyphae of pileus surface. Bars: a−b = 10 μm; c = 20 μm.