Taxonomic revision of kelp species with rhizome-like holdfast, Laminaria longipes Bory and Laminaria repens Ruprecht, from Russian Far Eastern seas

In this paper, we describe the historical background of one Laminaria J.V. Lamouroux species from the northern Pacific region. In the references, two different Laminaria species were recorded under the same name, Laminaria longipes Bory, due to errors in the labeling of authentic herbarium specimens, a very brief description, confusion of protologues, and the absence of type specimens. One of them, inhabiting the northern Atlantic Ocean, has rhizoids, whereas the second one from the Pacific Ocean has holdfast with rhizomes. The latter species was described by Ruprecht (1850) as Laminaria repens Ruprecht, however, due to various reasons this name was not scientifically accepted and in 19th century, this kelp species has been named differently, until the name L. longipes was universally accepted. None of its previous names were typified. We found original specimens collected in the 18th and 19th centuries that were used to describe these species, designated lectotypes and specified synonyms. We propose to return the name L. repens for the Pacific Laminaria species with rhizomes. Based on molecular- phylogenetic data of our specimens, we confirmed its validity and difference from another species with rhizomes distributed in the Pacific North America, L. sinclairii (Harvey ex JD Hooker & Harvey) Farlow, Anderson & Eaton. We also discuss developmental biology and ecology of L. repens from the Russian Far East, provide data on the geographical distribution of all known forms of this species and show that their areas, except for the Middle Kurile Islands, where they have been known so far, cover almost the entire distribution of this species.