First Southern Hemisphere record of Pezoloma marchantiae (Helotiales)

The characterization of a fungal species belonging to the class Leotiomycetes (Ascomycota, Fungi) is presented. The fungus develops on a thalloid liverwort of the genus Marchantia, collected in Nothofagus forests in Tierra del Fuego (Chilean Patagonia). The species identity was determined using an integrative approach combining vital taxonomy and phylogenetic analyses based on the ITS region of ribosomal DNA. Phylogenetic inference, based on 55 reference sequences from the family Discinellaceae, placed the specimen within the Pezoloma marchantiae clade with high statistical support. This agrees with previous molecular records from the Northern Hemisphere and with fungal endophytic sequences derived from Marchantia polymorpha. A detailed description based on living features of this first known collection from the Southern Hemisphere is provided, including macro- and micromorphological characters together with a comparative table including other species of the genus Pezoloma. This finding significantly extends the known biogeographical range of P. marchantiae and contributes to the understanding of hidden fungal diversity in austral Nothofagus forests. It also highlights the need for integrative studies combining morphological and molecular data to resolve the taxonomy of poorly sampled lineages within Leotiomycetes, particularly those associated with bryophytes.