Westerdykella formosana K. W. Cheng & H. A. Ariyaw., 2025

Cheng, Kai-Wen, Yang, Jiue-in, Srimongkol, Piroonporn, Stadler, Marc, Karnchanatat, Aphichart & Ariyawansa, Hiran A., 2025, Fungal frontiers in toxic terrain: Revealing culturable fungal communities in Serpentine paddy fields of Taiwan, IMA Fungus 16, pp. e 155308-e 155308 : e155308-

Westerdykella formosana K. W. Cheng & H. A. Ariyaw. sp. nov.

Fig. 16

Typification.

TAIWAN • Wanrung Township , Hualien County, 23°42'40.3"N, 121°24'48.2"E, serpentine soil in rice field, 2 nd November 2022, K. W Cheng, holotype, NTUPPMH 22-218 (Permanently preserved in a metabolically inactive state), ex-holotype NTUPPMCC 22-255 , ex-isotype NTUPPMCC 22-256 to 259 .

Etymology.

Named after Formosa, the former name of Taiwan, where the type specimen was collected.

Description.

Sexual morph Cleistothecia 250–430 µm diam, non-ostiolate, globose, glabrous, mostly superficial, some submerged in PDA, dirty gray when immature, black when mature. Peridium single-layered, brown, translucent, membranous, angular cells. Asci subglobose to globose, hyaline when immature, 32 - spored, 15.7–21.0 µm × 14.6–18.4 µm (x ̄ = 18.3 × 16.3 µm, L / W ratio = 1.1, n = 30). Ascospores ellipsoidal, smooth, subhyaline to light brown, 1 to 3 guttules, no germ-slits, 3.4–6.4 µm × 1.8–3.2 µm (x ̄ = 5.2 × 2.6 µm, L / W ratio = 2.01, n = 50). Asexual morph undetermined.

Culture characteristics.

Colony exhibits rapid growth, reaching 80 mm diam with flat, sparse aerial mycelium, creamy white, surface and margins smooth, pale gray in central region due to the presence of cleistothecia.

Notes.

Westerdykella formosana forms a distinct clade in our phylogenetic analysis (Fig. 13 and Suppl. material 2: figs S 1, S 2). The ex-type strain of W. formosana ( NTUPPMCC 22-255 ) exhibits significant genetic divergence from its closest relative, the ex-type strain of W. aquatica (JAUCC 1788) , with 94.7 % identity in the ITS region (392 / 414 bp, including 1 gap), and from the representative strain PY 1 of W. aquatica in the tub 2 gene (96.7 % identity; 857 / 886 bp). Morphologically, W. formosana produces larger asci but smaller ascospores compared to its phylogenetically closest relative, W. aquatica (x ̄ = 18.3 × 16.3 µm versus 15.3 × 14.1 µm; x ̄ = 5.2 × 2.6 µm versus 6.5 × 2.9 µm). Additionally, W. formosana lacks the yellow hue observed in PDA cultures of W. aquatica (Fig. 16 ; Song et al. 2020). Based on molecular, morphological, and cultural differences, we propose our five strains ( NTUPPMCC 22-255 to 22-259) as a novel species, Westerdykella formosana . Further morphological comparisons with other Westerdykella species are provided in Suppl. material 1: table S 4.

Figures

Figure 13. Maximum likelihood (ML) phylogenetic tree based on a concatenated dataset of ITS, LSU, and tub 2. In total, 56 strains representing 17 taxa were included in the concatenated dataset, with 2314 characters (ITS 459 bp, LSU 865 bp, and tub 2 990 bp) including alignment gaps. The tree was rooted with Preussia funiculata Huhndorf 2577 and P. typharum CBS 107.69. MLB ≥ 70 % and BPPs ≥ 0.95 were shown at each node; values lower than these thresholds are indicated by a hyphen (–). The scale bar indicates the number of estimated substitutions per site. The strains introduced in this study are in red and novel species are in bold. The ex-type strains are marked with T.

Figure 16. Morphology of Westerdykella formosana NTUPPMCC 22-255. A, B 14 - days-old colony on PDA; C Ascomata; D Immature ascoma; E Squashed ascomata; F Peridium; G, H Immature ascus; I Ascus; J, L Ascospore; K Immature ascospore. Scale bars: 100 µm (C, E); 200 µm (D); 20 µm (F – J); 5 µm (K, L).