Proposal of a new brown algal species, Mesogloia japonica sp. nov. (Chordariaceae, Phaeophyceae), and transfer of Sauvageaugloia ikomae to Mesogloia

Abstract

ABSTRACTA molecular phylogeny using mitochondrial cox1 and cox3 and chloroplast atpB, psaA, psbA and rbcL gene sequences revealed that the Japanese endemic brown alga Sauvageaugloia ikomae (Ectocarpales s.l.) is phylogenetically distant from the generitype S. divaricata described from Europe. It also suggests the occurrence of an undescribed species in the Seto Inland Sea and the Pacific coast of the Tohoku Region; whereas, S. ikomae is distributed in the Sea of Japan. The new species is genetically distinct from S. ikomae and is morphologically distinguishable in having thicker erect thalli with a more developed subcortical layer. In the phylogeny, the clade of Japanese Sauvageaugloia was sister to Mesogloia, both nesting in the clade of Cladosiphon species. Because ectocarpalean taxa are considered to be oversplit at generic rank compared to genetic divergence within the order, we refrain from describing a new genus for S. ikomae and the new species and instead suggest placing them in Mesogloia. We therefore propose the establishment of the new species Mesogloia japonica and a new combination M. ikomae. We also propose including Liebmannia leveillei in the genetically indistinguishable Mesogloia vermiculata.