Hydnum albodentum Yonglan Tuo, Bo Zhang & Yu Li sp. nov.

Fig. 3 A – G

Etymology.

The specific epithet “albodentum” refers to the pure white coloration of the fungal spines.

Holotype.

China • Anhui Province, Lu’an City, Jinzhai County, Yanzihe Town, 31°18'20"N, 115°55'32"E, Elevation: ca. 752 m. on soil in mixed forests (Quercus serrata Thunb. and Cunninghamia lanceolata (Lamb.) Hook.), 10 September 2023, Yonglan Tuo FJAU 66580. GenBank accession numbers: ITS = PV 997562, tef 1-α = PX 026328.

Diagnosis.

H. albodentum differs from other Hydnum species primarily in its medium-sized (7.93–6.78 μm), elliptical spores (Q = 1.13–1.25), and the presence of a white tomentum covering the pileus margin.

Description.

Basidiocarps small, solitary, 25.5–40.5 mm in height, fleshy when fresh. Pileus 27.5–55.5 mm wide, brownish orange to light brown (6 C 6–6 D 7), convex to plano-convex when mature, surface smooth, margin incurved and covered with white (4 A 1) tomentum. Context 2.5–4.5 mm thick, white (4 A 1). Hymenophore hydnoid, spines fleshy, non-decurrent, conical, sparse, 1–2 spines / mm 2; surface white (4 A 1), 3.0– 7.5 mm long, 0.5–1.5 mm diameter. Stipe cylindrical, 21.5–35.0 × 8.5–10.5 mm, solid, central, equal to slightly enlarged at the base, white to light brown (4 A 1–6 C 6), covered with white basal mycelium, brownish orange when handled. Odor mild or fruity.

Basidiospores (7.0) 8.0–8.5 (9.0) × (5.5) 6.0–7.0 (8.0) μm, av. L = 7.93 μm, av. W = 6.78 μm, Q = (1.0) 1.13–1.25 (1.33), av. Q = 1.17, ellipsoid, thin-walled, smooth, hyaline in 3 % KOH, some with granular contents; hilar appendix 0.5–1.0 μm long. Basidia (30.0) 32.5–45.0 (55.0) × (8.0) 9.0–10.0 (12.0) μm, subcylindric, some with granular contents and hyaline oily droplets; sterigmata 2–5, 4.0–5.0 × 0.5–1.0 µm, conical, thin-walled, smooth. Basidioles 25.0–32.0 × 7.0–9.0 μm, numerous, smaller than basidia, some with granular contents. Subhymenium trama filamentous, hyphae 2.5–3.0 μm wide, thin-walled, hyaline in 3 % KOH. Hyphae of spines 5.0–7.0 μm, thin-walled, apex cylindrical. Pileipellis composed of cylindrical hyphae, slightly interwoven; terminal elements cylindrical at apex, cells 65.5–105.5 × 8.5–10.0 μm. Stipitipellis composed of cylindrical hyphae, slightly interwoven, 6.0–7.5 μm wide, terminal elements rounded at apex. Clamp connections present.

Habitat and distribution.

The species occurs solitarily in a mixed forest (Q. serrata and C. lanceolata) within the buffer zone of Tianma National Nature Reserve, China (ca. 700–800 m, subtropical monsoon climate). The forest is subject to human disturbance (grazing, thinning, and proximity to villages at approximately 1.5–2.5 km). The specimen was collected at a distance of 45.6 cm from a C. lanceolata tree (DBH: 23.6 cm) and at a distance of 85.6 cm from a Q. serrata tree (DBH: 15.6 cm). Soil temperature was 12.1 ° C, soil volumetric water content was 25.3 %, soil pH was 5.9, air temperature was 24.2 ° C, and relative humidity was 88.5 %. Soil temperature, moisture content, and pH were measured at the time of sample collection; air temperature and humidity were monitored over the long term within the sample plot (measurements were taken at 10 - minute intervals; these data are mean values calculated over the 3 days preceding and following sample collection).

Additional specimens examined.

China • Anhui Province, Lu’an City, Jinzhai County, 31°18'41"N, 115°55'01"E, Elevation: ca. 742 m. on soil in Q. serrata and C. lanceolata mix forests, 10 September 2023, Yonglan Tuo FJAU 66581. GenBank accession numbers: ITS = PV 997563, tef 1-α = PX 026329.

Notes.

Morphologically, H. albodentum is similar to H. pallidomarginatum in having small basidiocarps (27.5–55.5 mm vs. 20.0–35.0 mm), but it is distinct from H. pallidomarginatum in having smaller basidiospores (7.93 × 6.78 μm vs. 8.75 × 6.99 μm) and a brownish orange to light brown pileus.

In the phylogenetic tree, the sequences of H. albodentum cluster together, forming a distinct lineage and a sister clade with H. flabellatum within subgenus Pallida.