First record of a cylindrical Dipterocladia (Ceramiales, Delesseriaceae), D. cylindrica sp. nov., from Korea based on morphological and molecular analyses

Abstract We describe a new species, Dipterocladia cylindrica, found in the subtidal zone of the eastern and southern coasts of Korea. This species has cylindrical branches with numerous sub-dichotomously branching monosiphonous determinate branchlets without adventitious filaments, heavy cortication throughout the thallus, and alternating clockwise periaxial cell formation. The external features of the new species are closer to those of the genus Dasya than to those of Dipterocladia, which have flattened thalli with pairwise distichously arranged monosiphonous pseudolateral and polysiphonous determinate laterals. However, based on the combined results of plastid rbcL and mitochondrial COI–5P sequences, the molecular phylogenetic relationships clearly indicate that our specimens belong to the genus Dipterocladia. We also detected more meaningful morphological characters for delineating the genus within the subfamily Dasyoideae by comparing the morphology and phylogeny, but we could not find unique characters for each clade. Further studies based on reproductive morphology and molecular phylogeny for delimiting the generic boundaries are needed.