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

Fig. 4 A – F

Etymology.

The specific epithet “albotomentosum” refers to the white tomentum covering the pileus and stipe of immature basidiocarps.

Holotype.

China • Anhui Province, Lu’an City, Tianma National Nature Reserve, 31°13'10"N, 115°46'53"E, Elevation: ca. 817 m. on soil in mixed forests (Quercus variabilis Blume and Pinus hwangshanensis W. Y. Hsia), 8 August 2023, Yonglan Tuo FJAU 66568. GenBank accession numbers: ITS = PV 329851, tef 1-α = PP 357256.

Diagnosis.

H. albotomentosum differs from other Hydnum species in its relatively small basidiocarps, short spines (0.5–2.0 mm), and the presence of a white tomentum covering the pileus surface when immature, which disappears upon maturity.

Description.

Basidiocarps small, solitary, 22.0–30.0 mm in height, fleshy when fresh. Pileus 16.5–29.5 mm wide, pale orange to deep orange (5 A 3–4 A 8), convex to plano-convex when mature, margin incurved, surface covered with white (4 A 1) tomentum when immature, tomentum disappearing upon maturity. Context 2.5–5.0 mm thick, white (4 A 1). Hymenophore hydnoid, spines fleshy, non-decurrent, conical, sparse, 1–2 spines / mm 2; surface white to yellowish white (4 A 1–4 A 2), 0.5–2.0 mm long, 0.25–0.5 mm diameter. Stipe cylindrical, 20.0–30.0 × 7.0–10.0 mm, solid, central, equal to slightly enlarged at the base, white to deep orange (4 A 1–4 A 8), covered with a large amount of white basal mycelium; Stipe at first whitish, staining pale brownish orange when handled. Odor mild or fruity.

Basidiospores (6.0) 7.0–8.0 (8.5) × (5.5) 6.5–7.0 (8.0) μm, av. L = 7.11 μm, av. W = 6.72 μm, Q = 1.0–1.14, av. Q = 1.06, globose to subglobose, thin-walled, smooth, hyaline in 3 % KOH, some with granular contents; hilar appendix 0.5–1.0 μm long. Basidia (33.0) 36.0–42.0 (46.0) × (7.5) 9.0–10.0 (12.0) μm, clavate to suburniform, some with granular contents and hyaline oily droplets; sterigmata 2–4, 4.0–6.0 × 1.0–2.0 µm, conical, thin-walled, smooth. Basidioles (28.0) 30.0–38.0 (42.0) × (6.0) 8.0–10.0 (12.0) μm, numerous, smaller than basidia, some with granular contents. Subhymenium trama filamentous, hyphae 3.0–4.0 μm wide, thin-walled, hyaline in 3 % KOH. Hyphae of spines 6.5–7.0 μm, thin-walled, apex cylindrical. Pileipellis composed of cylindrical hyphae, subparallel to slightly interwoven; terminal elements cylindrical at apex, cells 56.0–105.0 × 5.5–7.0 μm. Stipitipellis composed of cylindrical hyphae, slightly interwoven, 4.0–6.0 μm wide, terminal elements rounded at apex. Clamp connections present.

Habitat and distribution.

The species occurs solitarily in a mixed forest (Q. variabilis and P. hwangshanensis) within the buffer zone of Tianma National Nature Reserve, China (ca. 800–900 m, subtropical monsoon climate). The forest is subject to human disturbance (grazing, thinning, and proximity to villages and towns at approximately 0.5–3.5 km). Specimens were collected at a distance of 139.5 cm from a P. hwangshanensis tree (DBH: 50.6 cm) and at a distance of 85.6 cm from a Q. variabilis tree (DBH: 25.6 cm). Soil temperature was 24.1 ° C, soil volumetric water content was 24.2 %, soil pH was 5.2, air temperature was 25.6 ° C, and relative humidity was 85.6 %. 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, Tianma National Nature Reserve, 31°13'14"N, 115°46'55"E, Elevation: ca. 856 m. on soil in Q. variabilis and P. hwangshanensis mixed forests, 17 July 2023, Yonglan Tuo FJAU 66569. GenBank accession numbers: ITS = PV 329852, tef 1-α = PP 357257.

Notes.

Morphologically, H. albotomentosum is similar to H. ibericum in having a white to cream pileus and small basidiocarps (16.5–29.5 mm vs. 22.0–30.0 mm), but it is distinct from H. ibericum in having smaller basidiospores (7.11 × 6.72 μm vs. 8.2 × 6.4 μm).

In the phylogenetic tree, the sequences of H. albotomentosum form a distinct lineage and group within a large subclade with strong support (100 % ML and 1.00 BPP) together with H. vesterholtii, H. ibericum, H. subtilior, H. tottoriense, H. flabellatum, H. pallidomarginatum, and H. luteoalbum. Based on the morphological characteristics described above and the phylogenetic results, H. albotomentosum should be classified as a member of subgenus Pallida.