Notes on Phylogenetic Relationships in <i>Mariannaea</i> (Hypocreales, Sordariomycetes) with a New Geographical Record of <i>M. aquaticola</i>

Mariannaea is a distinct hyphomycetous genus in Nectriaceae that has undergone substantial taxonomic revisions over the past decades through integrative morphological and molecular studies. In this article, we document Mariannaea aquaticola as a new record from the Philippines, based on collections from submerged decaying wood in a freshwater lake, and reassess species boundaries within the genus using morphology and multigene phylogenetic analyses (ITS, LSU, and TUB2). Phylogenetic reconstruction of 76 taxa confirms the monophyly of Mariannaea and places the Philippine isolates within a strongly supported clade corresponding to M . aquaticola . Detailed morphological observations of the asexual morph are consistent with previous descriptions of the species. Comparative sequence analyses reveal negligible genetic divergence among M . aquaticola , M . humicola , and M . hyalina , with no phylogenetic structure supporting their recognition as separate taxa. Consequently, M . humicola and M . hyalina are here reduced to synonymy under M . aquaticola . In addition, phylogenetic evidence supports synonymizing M . terricola with M . punicea . The discovery of M . aquaticola in the Philippines expands the species’ known distribution. This underscores the ecological versatility of Mariannaea across terrestrial and freshwater habitats, contributing to a more comprehensive understanding of nectriaceous fungal diversity and biogeography.