Pseudogymnoascus ramosus Childress & Quandt, 2025

Childress, Mary K., Dragone, Nicholas B., Young, Benjamin D., Adams, Byron J., Fierer, Noah & Quandt, C. Alisha, 2025, Three new Pseudogymnoascus species (Pseudeurotiaceae, Thelebolales) described from Antarctic soils, IMA Fungus 16, pp. e 142219-e 142219 : e142219-

Pseudogymnoascus ramosus Childress & Quandt sp. nov

Figs 5 , 6

Etymology.

The name refers to heavily branched hyphae with gregarious groupings of conidiophores.

Type.

Antarctica • Shackleton Glacier, Mount Franke , 84°37'35.52"S, 176°44'36.12"W, 485 m, from soil, 2 Jan 2018, coll. B. Adams, G. Schellens, N. Fierer & M. Shaver-Adams. Holotype 420 ASP, stored in a metabolically inactive state in the CFMR Herbarium, while ex-type metabolically active material is stored in the Reference Culture Collection at the CFMR .

Description.

On CMA and PDA hyphae branched, septate, hyaline, smooth, 0.9–1.9 μm wide. Racquet hyphae absent. Fertile hyphae bearing aleurioconidia, sessile or stalked. Arthroconidia not observed. Conidiophores abundant, often grouping gregariously but sometimes solitary, erect, arising in acute angles with the main axis, hyaline, smooth, usually bearing verticils of two to four branches arising from the stipe at an acute angle. Conidiophores more abundant on CMA than PDA. Aleurioconidia are pyriform to clavate or obovoid with a broad truncate basal scar, 2.8–4.6 × 1.7–3.2 μm (av = 3.7 × 2.5 μm, n = 50), in conidiophores separated by connective cells. Intercalary conidia are rare, pyriform to clavate, or subglobose, 2.7–4.6 × 1.9–2.7 μm (av = 3.5 × 2.3 μm, n = 7), in conidiophores separated by connective cells. Ascomata absent.

Culture characteristics.

On OA, colonies reach 14 mm in diameter after 28 days at 15 ° C, round, slightly irregular, appressed, colorless to white, consisting of immersed and hyaline hyphae, small clumps of white cottony aerial mycelium, exudates and diffusible pigments absent; reverse white. On CMA, colonies reach 14 mm in diameter after 28 days at 15 ° C, round, slightly irregular, dense and slightly umbonate, floccose, white, abundant exudates in the form of transparent pale pink large droplets, diffusible pigments absent; reverse brown. On SDA, colonies reach 14 mm in diameter after 28 days at 15 ° C, round, slightly irregular, slightly raised and umbonate, floccose, shallow radial grooves, white at center, pink to white margin, exudates and diffusible pigments absent; reverse beige. On PDA, colonies reach 15 mm in diameter after 28 days at 15 ° C, irregular, raised, umbonate, floccose, white, dense, exudates initially in the form of transparent and colorless droplets and aging to dark red within two weeks, brown diffusible pigments; reverse brown. Growth occurred at 5 ° C and 15 ° C, with very minimal growth at 25 ° C; optimum growth was observed at 15 ° C. No culture attenuation was observed.

Distribution.

Mount Franke and Schroder Hill, Shackleton Glacier, Antarctica.

Ecology / substrate.

Cultured from Antarctic soil.

Additional specimen examined.

Schroder Hill, 508 ASP, ibid.

Genbank accession numbers.

ITS = PQ 453554, LSU = PQ 453559, MCM 7 = PQ 497092, RPB 2 = PQ 497097, TEF 1 = PQ 497100.

NCBI BioSample Genome Accession.

SAMN 40283454 .

Note.

Pseudogymnoascus ramosus has been placed as a member of clade Q (Figs 1 , 2 ), which also includes unidentified species VKM F-4520 ( Leushkin et al. 2015). Fig. 1 shows Q as sister to clade A, B, C, and D, however the placement of clade Q in relation to these clades has low bootstrap support. Leushkin et al. (2015) first introduced clade Q and had low bootstrap support for determining its overall placement with other clades in their gene tree. According to Fig. 2 , there is strong bootstrap support for clade Q being sister to clades B, E, F, G, H, I, J, K; but data are missing for clades A, C, and D to confirm this placement. A unique characteristic of P. ramosus not documented in any described species of Pseudogymnoascus is its heavily branched hyphae with gregarious groupings of conidiophores. It is also relatively slow growing, only reaching 14 mm in diameter after 28 days on OA, CMA, SDA, and 15 mm on PDA. Phylogenetically, our P. ramosus isolates, strain 420 ASP and 508 ASP, form a well-supported independent lineage with a bootstrap value of 100, being the first described species in clade Q.

Figures

Figure 1. Maximum likelihood (ML) phylogenetic tree of Pseudogymnoascus based on the concatenated dataset of five genes (ITS, LSU, MCM 7, RPB 2, TEF 1). ML bootstrap values ≥ 70 are shown above branches. New species described here are highlighted in bold and red. The scale bar indicates 0.03 nucleotide changes per site.

Figure 2. ML phylogeny of Pseudogymnoascus based on an alignment of 1496 concatenated orthogroups with single-copy genes. ML bootstrap values ≥ 75 are shown above branches. New species are highlighted in bold and red. The scale bar indicates 0.09 amino acid changes per site.

Figure 5. Pseudogymnoascus ramosus sp. nov. colony morphology at 5 ° C and 15 ° C after 28 days on CMA, OA, PDA, and SDA.

Figure 6. Pseudogymnoascus ramosus sp. nov. A, B, D conidiophores C conidia E, F fertile hyphae bearing aleurioconidia. Scale bars: 10 µm.