Neohelicomyces tropicus T. H. Tan & J. Ma sp. nov.

Fig. 3

Etymology.

The species epithet “ tropicus ” refers to the tropical climate in which the species occurs.

Holotype.

GZAAS 25-0675.

Description.

Saprobic on decaying wood in a terrestrial habitat. Sexual morph Undetermined. Asexual morph Hyphomycetous, helicosporous. Colonies on natural substrate superficial, gregarious, with a little of crowded, glistening conidia, white. Mycelium partly immersed, partly superficial, composed of hyaline to pale brown, branched, septate, smooth hyphae. Conidiophores 139–175 × 4–5.5 μm (x ̄ = 154 × 4.5 μm, n = 25), macronematous, mononematous, erect, cylindrical, straight or slightly flexuous, branched or unbranched, septate, subhyaline to pale brown, thick-walled. Conidiogenous cells 10–17 × 3–4 μm (x ̄ = 14 × 3.5 μm, n = 25), holoblastic, monoblastic or polyblastic, integrated, terminal or intercalary, cylindrical, with denticles, subhyaline to pale brown, smooth-walled. Conidia solitary, acropleurogenous, helicoid, tapering towards the rounded ends, developing on tooth-like protrusion, 15.5–20 μm diam. and conidial filament 2–3.5 μm wide (x ̄ = 17.5 × 2.5 μm, n = 20), 95–140 μm long (x ̄ = 116 μm, n = 20), tightly coiled up to 3 times, becoming loosely coiled when the conidia are young and not becoming loose when mature in water, aseptate, guttulate, hyaline, smooth-walled.

Culture characteristics.

Conidia germinated on PDA and produced germ tubes within 14 h. Colonies on PDA reached 25 mm in diameter after 38 days of incubation at 25 ° C with a circular shape, flat surface, and entire margin, pale brown to brown; the reverse was pale brown to brown.

Material examined.

China • Hainan Province, Baoting Li and Miao Autonomous County, Qixianling Hot Spring National Forest Park, on decaying wood in a terrestrial habitat, 2 November 2024, Ting-Hong Tan & Jian Ma, Q 45 (GZAAS 25-0675, holotype), ex-type living culture GZCC 25-0661 • ibid., Q 47 (GZAAS 25-0690, paratype), living culture GZCC 25-0662.

Notes.

In the phylogenetic analyses (Fig. 1), our isolates (GZCC 25-0661 and GZCC 25-0662) formed a well-supported sister clade to Neohelicomyces hainanensis (GZCC 22-2009), with 95 % ML and 1.00 BYPP values. Morphologically, N. tropicus (GZAAS 25-0675) and N. hainanensis (GZAAS 22-2009) are nearly identical in their conidiophores, conidiogenous cells, and conidia (Lu et al. 2022). However, nucleotide comparisons among the LSU, ITS, tef 1 - α, and rpb 2 sequence data between Neohelicomyces tropicus (GZCC 25-0661) and N. hainanensis (GZCC 22-2009) revealed differences of 4 / 815 bp (0.5 %, with no gaps), 23 / 482 bp (4.8 %, including 18 gaps), 15 / 912 bp (1.6 %, with no gaps), and 27 / 1,045 bp (2.6 %, with no gaps), respectively. Therefore, based on the molecular data, we introduce Neohelicomyces tropicus as a novel species.