Revealing the diversity of the genus Ulva (Ulvales, Chlorophyta) in southeastern Brazil, with a description of Ulva kanagawae sp. nov.

The green algal genus Ulva is one of the most widely distributed macroalgal genera. The taxonomy of Ulva is problematic due to its simple morphology. The study of the diversity of this genus has undergone great advances using molecular data, leading to changes in the taxonomic status of species, and the recognition of species complexes and cryptic species. Here we reassessed Ulva species from southeastern Brazil using molecular data. We recognized 10 taxa, among which only three previously reported species were confirmed by molecular data: U. compressa, U. lactuca and U. ohnoi, the latter recently recorded from insular waters in Fernando de Noronha Archipelago, northeastern Brazil. Our phylogenetic analyses and species delimitation methods strongly supported the establishment of Ulva kanagawae sp. nov. The species traditionally cited for southeastern Brazil, U. flexuosa, U. linza, U. rigida and U. paradoxa, proved to be misapplied names of U. tepida, U. aragoensis, U. ohnoi/U. lactuca and U. torta, respectively. One taxon, Ulva sp., remains unnamed and needs further studies. Ulva chaugulei and U. tanneri, both considered here as cryptogenic species, are new occurrences for Brazil expanding their geographic distribution to the Atlantic Ocean and western Atlantic Ocean, respectively. In addition, our analysis of sequences from type materials revealed that U. pseudo-ohnoi is a heterotypic synonym of U. conglobata. This first systematic molecular study of Ulva species in Brazil points out that more extensive sampling is needed to reveal the true diversity of the genus in Brazilian waters.