Dematiodidymosporum Y.S. Liang, W. Dong, K.D. Hyde & Doilom, in Dong et al., Fungal Diversity (2025)

Index Fungorum number: IF 903058; MycoBank number: MB 903058; Facesoffungi number: FoF 17151

Etymology – refers to dematiaceous didymospores of the fungus.

Saprobic on decaying wood. Sexual morph: Ascomata clustered, erumpent to almost superficial, subglobose, black, glabrous, unilocular, central ostiolate, shot papillate. Peridium two-layered, outer layer cells dark, thick-walled, inner layer cells pale, thin-walled, composed of cells of textura angularis. Pseudoparaphyses numerous, cellular, septate, hyaline. Asci 8-spored, bitunicate, clavate, shot pedicellate. Ascospores fusoid, straight, septate, darkened at the septum when mature, asymmetric, golden brown, rough-walled, with or without conspicuous sheath. Asexual morph: undetermined.

Type species – Dematiodidymosporum aquaticum Y.S. Liang, W. Dong, K.D. Hyde & Doilom

Notes – in the phylogenetic analysis, Dematiodidymosporum forms a distinct lineage within Dictyosporiaceae, and has close relationships with Pseudocoleophoma species (Fig. 1). Several studies have shown that Pseudocoleophoma appears polyphyletic (Dong et al. 2023; Zhang et al. 2023a; Feng et al. 2024). Our study has shown that Pseudocoleophoma species cluster into three distinct clades, viz., clade 1 (Pseudocoleophoma sensu stricto) comprising the type species P. calamagrostidis and its related species, clade 2 comprising two strains of P. puerensis, and clade 3 comprising P. guizhouensis and P. typhicola (Fig. 1).

Dematiodidymosporum shares the closest relationships with Pseudocoleophoma sensu stricto. However, Dematiodidymosporum differs greatly in having almost superficial ascomata, golden brown, rough-walled, asymmetric ascospores loosely arranged in the asci, and mature ascospores with a darkened septum. In contrast, all sexual species of Pseudocoleophoma in clade 1 have immersed to erumpent ascomata, hyaline, smooth, symmetric ascospores tightly arranged and overlapped in the asci, and without a darkened septum. In addition, the ascospores in Pseudocoleophoma sensu stricto are entirely fusiform with tapering ends, and deeply constricted by a septum, as well as mostly with a conspicuous, gelatinous sheath (Tanaka et al. 2015; Jayasiri et al. 2019; Zhang et al. 2023a). However, Dematiodidymosporum has fusoid ascospores with rounded apex and tapering base, and slightly constricted at the septum, without a sheath.

Pseudocoleophoma puerensis, a species in Pseudocoleophoma sensu lato, is comparable to Dematiodidymosporum, but differs in having immersed to erumpent ascomata, and brown, 3-septate ascospores (Lu et al. 2022). Immotthia is also comparable to Dematiodidymosporum, but differs in having densely aggregated ascomata arising from a large hypostroma, usually with a pore-like, inconspicuous ostiole or minute papilla, cylindrical or cylindric clavate asci, and overlapping 1–2-seriate, tightly arranged, pale yellowish to brown, or reddish brown ascospores (Jiang et al. 2021a). The phylogenetic analyses have indicated that they are genetically distinct genera (Fig. 1). Dematiodidymosporum is, herein, established as a novel genus within Dictyosporiaceae.

Figure 1 – Maximum likelihood consensus tree inferred from the combined ITS, LSU, and tef1-a multiple sequence alignments. Bootstrap support values for maximum likelihood (ML, first value) equal to or greater than 75% and Bayesian posterior probabilities from MCMC analyses (BYPP, second value) equal to or greater than 0.95 are given nearby the nodes. The scale bar indicates expected changes per site. The tree is rooted to Lentithecium clioninum KT 1220. Ex-type strains are indicated with “T”. The newly generated sequence is indicated in red.

Species