A molecular investigation of Canadian Scytosiphonaceae (Phaeophyceae) including descriptions of Planosiphon gen. nov. and Scytosiphon promiscuus sp. nov.

Abstract

Identification of macroalgae has been greatly facilitated by the use of molecular tools. Using the DNA barcode (COI-5P = 5′ end of cytochrome c oxidase 1), we have uncovered considerable genetic variation in Scytosiphon. Whereas only four species were recognized in North America [S. canaliculatus (Setchell & N.L.Gardner) Kogame, S. complanatus (Rosenvinge) Doty, S. dotyi M.J.Wynne, and S. lomentaria (Lyngbye) Link], mitochondrial COI-5P data resolved 11 genetic groups while nuclear ITS data, in combination with morphological observations, supported recognition of seven species. These seven groups were assigned to: Scytosiphon Atlantic complex, S. sp._J, S. canaliculatus, S. complanatus, S. dotyi, S. lomentaria, and S. promiscuus sp. nov. One of the two species of Scytosiphon most commonly reported in North America, S. dotyi, was absent in Canada. Overlooked variation was also uncovered among Canadian collections of Colpomenia and Petalonia, indicating cryptic diversity in these scytosiphonacean genera as well. Multigene phylogenetic analyses supported the transfer of Petalonia zosterifolia (Reinke) Kuntz, Scytosiphon gracilis Kogame, and S. complanatus to Planosiphon gen. nov. Further, the included species of Chnoospora and Colpomenia failed to form monophyletic groups indicating that substantial taxonomic work remains for this brown algal family.