Reinstatement of Laminaria multiplicata as Saccharina multiplicata comb. nov. ( Laminariales, Phaeophyceae ) based on morphological and molecular data

SUMMARY Laminaria multiplicata is an endemic species described from Eirineiskaya Gulf in the Sea of Okhotsk. In 2010, L. multiplicata was treated as conspecific with Saccharina gurjanovae (≡ Laminaria gurjanovae ), which was subsequently synonymized under S. latissima f. gurjanovae . In the present study, we conducted morphological and molecular analyses of freshly collected specimens exhibiting the Laminaria cf. multiplicata and L . cf. latissima morphotypes from Eirineiskaya Gulf. In addition, specimens of the Laminaria cf. multiplicata morphotype were morphologically compared with the holotype and isotype specimens of L. multiplicata . Morphological and anatomical analyses revealed no major differences between the Laminaria cf. multiplicata and L . cf. latissima morphotypes, except for the presence of conspicuous longitudinal folds on the blade and smaller subcortical cells. Molecular analyses based on mitochondrial COI, plastid RuBisCo, and nuclear ITS statistically supported these specimens as a member of the genus Saccharina . In particular, the Laminaria cf. multiplicata morphotype was placed in a well‐supported clade, distant from S. latissima (either from the Russian coast or from the Atlantic). Genetic distances between the specimens and S. latissima from the Russian coast were 2.7% for the COI gene (complete cds) and 1.2% for the RuBisCo region, further supporting the genetic independence of this taxon. Thus, we reinstate L. multiplicata as an independent species within the genus Saccharina as S. multiplicata comb. nov. At present, S. multiplicata is known only from its type habitat, the Eirineiskaya Gulf, with recent collections restricted to Malaya Molta Bay.