Novel Freshwater Ascomycetes from Submerged Plant Debris in the Zújar River (Extremadura Community, Spain)

Freshwater fungi remain insufficiently documented in the Mediterranean river systems despite their key roles in organic-matter turnover. Here, we surveyed filamentous fungi associated with submerged decaying plant debris in the Zújar River (Extremadura, southwestern Spain) using a culture-based approach combined with phenotypic characterization and multilocus phylogenetic analyses (ITS, LSU, rpb1, rpb2 and tef-1α). A total of 49 strains were isolated and identified, revealing a diverse assemblage of Ascomycota. Five taxa are described as new to science: Arachnopeziza torrehermosensis, Conioscypha clavatispora, Neoanungitea torrehermosensis, Ophioceras diversisporum and Polyscytalum submersum. Notably, Polyscytalum submersum represents the first record of the genus for the Iberian Peninsula, while Arachnopeziza torrehermosensis, Neoanungitea torrehermosensis and Ophioceras diversisporum constitute the first records of their respective genera for Spain (and Neoanungitea torrehermosensis also for Europe). In addition, phylogenetic evidence supports taxonomic refinements within the orders Magnaporthales and Conioscyphales, including the establishment of Protophioceras to accommodate Ophioceras sichuanense and the establishment of Protoconioscypha for two previously misclassified Conioscypha species. Overall, this first mycological report of submerged plant debris in the Zújar River substantially expands knowledge of freshwater fungal diversity in the region and provides a refined framework for the taxonomy of several lineages of aquatic-associated ascomycetes.