Towards a monograph of marine Verrucariaceae in Southern South America and maritime Antarctica: Integrative taxonomy reveals a previously unknown diversity

The family of predominantly lichen-forming Verrucariaceae, contains several lineages that have adapted to live in the stressful conditions of the intertidal and supralittoral zones of rocky seashores in both hemispheres. The marine Verrucariaceae has been the subject of several systematic and taxonomic studies over the past few decades, although these studies have primarily concentrated on groups from the northern hemisphere. This study aims to address the paucity of taxonomic studies in the southern hemisphere by examining a substantial number of specimens collected in Southern South America and maritime Antarctica over the past two decades by the authors. We opted for an integrative taxonomic approach that joins the characterization and measurement of morpho-anatomical characters, coupled together with molecular barcoding to produce species delimitations to overcome the difficulties derived by the scarcity of taxonomic characters and the high plasticity of those characters. We barcoded a total of 301 specimens using the universal barcode un fungi (nrITS) and used single-locus species delimitation algorithms (ASAP, PTP, GMYC) to produce candidate species hypothesis that were corroborated with the morphological data. Our findings indicate that the taxonomic diversity of the Southern Hemisphere Verrucaria marina group has been significantly underestimated in previous studies. A total of 27 species were found in the region, 21 of which represent new taxa for science. Thorough descriptions together with illustrations showing the main characters of the species are provided for each taxon. In addition, we explored the systematics of the new taxa. We reconstructed the phylogenetic relationships of the family based on on six molecular markers (ITS, mcm7, nrSSU, nrLSU, mtSSU, RPB1). Our results showed that marine Verrucariaceae from the studied area belong to two distinct and non-related clades. A small group of species were related to the northern hemisphere species Turgidosculum ulvae. The second and more numerous group, which included the characteristic species Mastodia tessellata for a clade sister to the European genus Verrucariopsis. The systematic consequences of our findings are discussed. None of the previously reported species from the northern hemisphere and considered bipolar were found during our study.