Epibryon brunneolum (W. Sun, Lei Su, M. C. Xiang and Xing Z. Liu) B. P. R. Lustosa, S. de Hoog, V. A. Vicente and Y. Song comb. nov.

Basionym.

Cladophialophora brunneola W. Sun, Lei Su, M. C. Xiang and Xing Z. Liu – Mycology 14: 330, 2023.

E. brunneolum genome exhibited the highest proportion of orthogroups with two genes compared with other Epibryaceae species (Fig. 1), showing greater protein diversity. Previous studies have shown that this species also has the highest number of CAZymes among rock-inhabiting Chaetothyriales (Fu et al. 2023). Rock-inhabiting fungi (RIF) experience severe fluctuations in temperature and humidity as they occupy sun-exposed rock surfaces (Quan et al. 2024). In this context, recent studies have demonstrated that RIF can exhibit expansions in cell wall biosynthesis, lipid metabolism, and stress-response pathways (Fu et al. 2025), which may explain their adaptation to such specialized niches.

In addition to mosses and hepatics, previous studies have reported several Epibryaceae isolates from lichens (Muggia et al. 2015). In the derived chaetothyrialean family Herpotrichiellaceae, heat tolerance is often associated with potential pathogenicity in humans, as seen in chromoblastomycosis caused by Cladophialophora carrionii (Deng et al. 2013). Moreover, associations between Cladophialophora species and lichens have been documented (Chang et al. 2023; Cometto et al. 2023; Costa et al. 2025; Keller et al. 2025). Related taxa such as Melanina, Muellerella, and Paracladophialophora — rock- and lichen-inhabiting fungi of uncertain phylogenetic placement within Chaetothyriales — show a similar affinity for lichenized habitats (Muggia et al. 2015, 2021; Cometto et al. 2023; Quan et al. 2024). These findings suggest that lichen symbiosis is not uncommon within the order. Expanded phylogenetic analyses incorporating newly described taxa, such as Pleostigma, have also revealed multiple lichen-associated species positioned between the Verrucariales and Chaetothyriales, indicating that lichen association may represent an ancestral state of both orders (Muggia et al. 2015, 2021; Costa et al. 2025).

Compared with other members of the Chaetothyriales, the Epibryaceae exhibit a distinct repertoire of enzymes related to cold stress tolerance (Fig. 4), as well as CAZymes and MEROPS peptidases (Fig. 3). The expansion of specific cold-related genes suggests that members of this family are well adapted to extremely low-temperature environments. All Epibryaceae species possess the cold shock protein A (CspA), an enzyme with RNA-binding activity that stabilizes ribosomal structures for protein translation under cold stress (Fang and Leger 2010). Previous work has shown that this enzyme is expanded among black fungi in the class Dothideomycetes isolated from Antarctic environments (Coleine et al. 2024), indicating its key role in fungal survival at low temperatures. The absence of ClpA / B, conserved site 2 (IPR 028299), in Epibryon species suggests a reduced tolerance to high temperatures, as this domain is known to protect cellular structures during heat stress (Barnett et al. 2000; Jaworek et al. 2014). Although its function in fungi remains poorly understood, studies indicate its importance for heat stress tolerance. Furthermore, the expansion of DNA recombination / repair protein Rad 51 (IPR 011941) observed in all members of Epibryaceae may contribute to UV radiation tolerance, as this gene encodes a protein involved in repairing DNA damage caused by UV light (Jung et al. 2016). This gene is also expanded in Antarctic black fungi of Dothideomycetes (Coleine et al. 2024), highlighting its potential role in resistance to high UV radiation in glacial environments. Together, these adaptations may explain the preference of Epibryaceae for psychrophilic habitats compared with other Chaetothyriales lineages.

The Chaetothyriales show expansions in several gene families, including AA 1 (laccase), AA 4 (vanillyl-alcohol oxidase), and S 09 X (carboxylesterase), as reported previously (Teixeira et al. 2017; Vicente et al. 2017; Moreno et al. 2017). The expansion of various CAZyme glycoside hydrolase families suggests that Chaetothyriales species possess numerous enzymes involved in plant biomass degradation compared with their ancestral group (Suppl. material 1: table S 3). This supports the hypothesis that these fungi may have originated in rock- and lichen-associated habitats and later evolved toward a saprobic lifestyle (Gueidan et al. 2014; Quan et al. 2024). Although the Epibryaceae display a similar pattern of gene family expansions, they also show contractions in certain auxiliary activity families, such as AA 7 (glucooligosaccharide oxidases), AA 9 (monooxygenases), and GH 12 (glucanases) (Suppl. material 1: table S 3). Additionally, members of the family possess the exclusive CBM 52 — binding to endo- 1, 3 - β-glucanase — an auxiliary enzyme that enhances β-glucanase activity in cell septation (Martín-Cuadrado et al. 2008). The specific role of this domain in the ecological adaptation of Epibryon remains to be elucidated. The reduced set of lignin- and polysaccharide-degrading enzymes, along with contraction in cysteine peptidases involved in thiol group hydrolysis (Shestakova et al. 2024), indicates a lower overall peptidolytic and ligninolytic capacity. These features likely contribute to the family’s preference for moss-associated habitats in cold environments, where lignin-rich plant material is less abundant and easily accessible carbon sources are supplied through a saprobiotic relationship (Gueidan et al. 2008; Stenroos et al. 2010; Muggia and Grube 2018; Costa et al. 2025).

The psychrophilic preference of Epibryon distinguishes it from other chaetothyrialean fungi and aligns it with lichenicolous fungi that inhabit rocks in boreal and Arctic climates. Its saprobiotic ecology with mosses and lichens suggests an atypical niche within the Chaetothyriales, as such ecology is rare in this order. Ascomycetes that are obligate bryophyte saprobes typically inhabit microsites such as leaf nerves or hyaline hair points in mosses, subterranean rhizoids, leaf borders or axils, and even individual leaf cells in foliose hepatics (Döbbeler et al. 2023). Most microniches described for Epibryon occur on the lower, dying, or dead leaves of various bryophyte species. Some species appear to exhibit host specificity (Döbbeler 1978, 1979, 1997; Döbbeler et al. 2023). However, despite extensive herbarium records, molecularly characterized isolates remain scarce (Stenroos 2010), limiting understanding of their ecological distribution. Our data indicate that the habitat preference of Epibryon species is broader, also encompassing lichens, soil, and the phyllosphere. Future sampling and molecular sequencing of Epibryon from underexplored regions will further clarify its apparent specialization for saprobic lifestyles on mosses, liverworts, and lichens in cold climates.