A re-evaluation of Palmaria (Palmariaceae, Rhodophyta) in the North-West Pacific

To understand the phylogenetic relationships within Palmariaceae and taxonomic position of the red algal species of genus Palmaria in the North Pacific and North Atlantic, a molecular study was undertaken of Palmaria sensu lato, Halosaccion and Devaleraea species based on sequence data of the nuclear ITS and plastid rbcL. The monophyly of the Palmariaceae was confirmed, although the genus Palmaria sensu lato was strongly supported as paraphyletic, comprising two independent clades, one of only P. palmata and the other, species from the North Pacific. The data also revealed that P. stenogona and P. marginicrassa were genetically most closely related to Devaleraea spp. These results changed the interpretation of the genera Palmaria and Devaleraea and supported a transfer of both Palmaria species to the genus Devaleraea, thus necessitating new combinations, D. stenogona and D. marginicrassa. In the interpretation proposed here, Palmaria sensu stricto is a monotypic genus with a single species P. palmata and apparently confined to the North Atlantic, while Devaleraea includes at least 10 species from the North Pacific among which D. ramentacea occur in both the North Atlantic and North Pacific. These data are in accordance with earlier studies. Nevertheless, more studies are needed to revise the taxonomy of Palmaria hecatensis in order to complete the revision of Palmaria sensu lato and Devaleraea in the northern hemisphere. Our results also confirm the generic affinities of Halosaccon yendoi, recovered from Devaleraea in 2016. Based on a study of seasonal variability in the morphology of D. stenogona, a detailed description of the species D. stenogona is presented.