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ABSTRACT
Recently, synonymizing Eisenia with Ecklonia was suggested based on a molecular phylogeny using the rbcL gene and ITS1–5.8S rDNA sequences. However, in a multigene molecular phylogeny based on mitochondrial cox1, cox3 genes and the atp8–16S rDNA region, as well as the plastid atpB, psaA, psbA and rbcL genes, Ecklonia spp. formed a monophyletic clade supported by high statistical values, and Eisenia spp. showed monophyly depending on analytical methods. The Japanese Eisenia species that used to be identified as Eisenia arborea (E. arborea sensu Arasaki) was shown to be genetically distant from E. arborea from the NE Pacific and E. bicyclis from Japan. Eisenia spp. were morphologically distinct in having a split meristematic zone in the mature thallus forming a dorsi-ventral blade with false branches. Therefore, we propose reinstatement of Eisenia as an independent genus and describe a new species, Eisenia nipponica (= E. arborea sensu Arasaki) from Japan. E. nipponica is distributed on the Pacific Coast of central Honshu, having a separate geographic range from E. bicyclis, which is distributed on the Pacific coast of eastern Honshu and the Sea of Japan coast of north-western Honshu and northern Kyushu.
Acknowledgements
We are grateful to Dr Eric Henry for critically reading and improving the manuscript, Dr Kathy Ann Miller for her help in examining specimens in UB, Dr Jessie Alstatt for providing field data of E. arborea, Drs Akira Kurashima, Tatsuya Ishikawa, You Kato and Taku Yoshimura for their support in collecting specimens. Part of the study was supported by a JSPS Grant-in-Aid for Scientific Research (No. 16H04832) to H.K.
Disclosure statement
No potential conflict of interest was reported by the authors.
Supplementary Information
The following supplementary material is accessible via the Supplementary Content tab on the article’s online page at http://10.1080/09670262.2019.1692911
Supplementary table S1. Origins of samples and sequence data used for molecular analyses, including their database accession numbers.
Supplementary table S2. List of primers used for polymerase chain reaction (PCR) and sequencing.
Supplementary fig. S1. Holotype specimen of Eisenia nipponica sp. nov. (SAP115478), collected at Mugisaki, Shima, Mie, Japan on 2 April 2019 by H. Kawai.
Supplementary fig. S2. Neighbour-joining (NJ) phylogenetic tree based on concatenated DNA sequences of mitochondrial cox1, cox3 genes, atp8–16S rDNA region, and chloroplast psaA, psbA, atpB, rbcL gene sequences (Total 8223 bp). Numbers below the branches indicate the bootstrap values. Only the BP (≥50%) are shown.
Author contributions
H. Kawai: Original concept, collection of specimens, morphological studies, drafting and editing manuscript; Shingo Akita: genetic analyses; Kazuki Hashimoto: genetic analyses; Takeaki Hanyuda: collection of specimens, genetic analyses.