Molecular Relationships of Giant Kelp (Phaeophyceae)

Giant kelp, despite the economic and ecological value, is much confused in taxonomy. To discuss possible changes of the current classification system, we introduce published results and newly analysed sequences of both nuclear ribosomal DNA and plastid-encoded RuBisCo spacer. All members of the Alariaceae, Laminariaceae, and Lessoniaceae are grouped into a single monophyletic clade, while each family is not monophyletic. Eight groups are recognized: i) Egregia group, ii) Alaria group, iii) Laminaria group, iv) Hedophyllum group, v) Ecklonia group, vi) Agarum group, vii) Lessonia group, and viii) Macrocystis group. This results appear not to support the current familial system of advanced kelp, and rather suggest that a single family like Laminaria and Kjellmaniella are necessary because of their paraphyly.