Multi-locus phylogenetic analyses and morphology reveal new species, new records, and taxonomic updates of saprobic Dothideomycetes and Sordariomycetes from freshwater habitats in China

Lignicolous freshwater fungi are important for decomposing lignocellulose in woody litter, releasing nutrients, and softening wood, making it more palatable to detritus feeders in water. In this study, 13 lignicolous freshwater fungi were collected and isolated from Jiangxi and Zhejiang provinces, China. Combining morphological characteristics with multi-locus phylogenetic analyses (ITS, LSU, SSU, TEF 1-α, TUB 2, and RPB 2), these samples were identified as 10 new species, two new records, and a new collection belonging to 10 genera, eight families, and seven orders. Furthermore, phylogenetic analyses for each genus were updated, and the current research status and existing taxonomic challenges of these genera are discussed. Additionally, four synonymies are proposed within the genus Distoseptispora , further clarifying the ambiguous species boundaries in phylogenetic analyses. This study contributes to filling a gap in the research on fungal diversity in East China and improves our understanding of their ecological roles in freshwater ecosystems.