Clavariadelphus acuminatus X. L. Gao & P. Zhang, 2025

Clavariadelphus acuminatus X. L. Gao & P. Zhang sp. nov.

Diagnosis.

Differs from other Clavariadelphus species in that the apex of the basidiomata is acuminate and pale to brownish yellow or golden-brown in color.

Type.

China • Yunnan Province, Lufeng County, 25°24'02"N, 101°76'10"E, 2300 m asl., 4 September 2023, leg. X. L. Gao ( holotype MHHNU 12163 ) .

Etymology.

Acuminatus (Latin) refers to the acuminate apex of the basidiomata.

Description.

Basidiomata up to 15 cm high, 0.4–0.8 cm in diameter at the base, 0.8–1.2 cm in diameter in the middle, slightly tapering at both ends, simple, initially narrowly cylindrical, narrowly fusiform after maturity, mostly flexuous; hymenium initially smooth, then longitudinally rugose with age, pale (2 A 2) to pale orange (5 A 3) to apricot (5 B 6); apex fertile, obtuse to acute, smooth to rugose, darker than the hymenium with age, pale to brownish yellow (5 C 8) or golden brown (5 D 7); base terete, almost smooth, white to cream (4 A 3); context solid when young, gradually becoming soft and spongy with age. Odor and taste not recorded.

Hymenium extending over the apex of the basidioma, composed of basidia and leptocystidia. Basidia 75–99 × 8.5–13 µm, narrowly clavate, pale yellow in KOH, smooth, thin-walled, clamped, 4 sterigmata (rarely 2), 6–12 µm tall, with numerous granular contents and guttules. Basidiospores [60 / 3 / 2] 8–9.6 (– 10.0) × 6–7.8 (– 8.0) µm [ Q = (1.12 –) 1.14–1.50 (– 1.60), Q m = 1.36 ± 0.10], ellipsoid to broadly ellipsoid, with a prominent apiculus, and several oleiferous guttules within the spores, pale yellow in KOH, inamyloid, thin-walled, smooth. Leptocystiada 45–69 × 2–4 µm, mostly clavate, hyaline, smooth, clamped, with branches. Contextual hyphae 4–6 µm in diameter, thin-walled, clamped.

Ecological information and distribution.

Solitary, scattered or gregarious on the ground in mixed coniferous and broadleaved forest at elevations of 2300–2400 m. Southwestern China.

Additional material examined.

China • Yunnan Province, Gucheng District, Kainan Street , 26°77'41"N, 100°26'77"E, 2400 m asl., 9 September 2023 ( MHHNU 12164 ) .

Comments.

Clavariadelphus acuminatus is distinguishable from other Clavariadelphus species by the distinctive acuminate apex of the basidiomata. Morphologically, the taxon is similar to C. khinganensis in the color of the basidiomata, but the apex in C. khinganensis is obtuse or broadly rounded. In the phylogenetic analysis, C. acuminatus was the closest relative to C. pseudoelongatus with strong support ( PP 1, BS 100 %). Although the two species occupy a similar habitat, and have a subacute apex and flexuous basidiomata, in C. acuminatus the basidiomata have a brighter color and more strongly acute apex. Clavariadelphus acuminatus has pale to pale orange to apricot basidiomata, whereas C. pseudoelongatus has ecru-drab to light purple-drab basidiomata. In addition, microscopic features distinguish these species: C. acuminatus has smaller basidiospores (8–9.6 × 6–7.8 µm vs. 9.8–11.0 × 6.4–9.5 µm) and shorter basidia (75–99 × 8.5–13 µm vs. 81–113 × 8–13 µm). Thus, C. acuminatus and C. pseudoelongatus can be distinguished by the color of the basidiomata, and dimensions of the basidiospores and basidia.