Phylogenetic affinities of genera Acanthopeltis and Yatabella (Gelidiales, Rhodophyta) inferred from molecular analyses

Phylogenetic affinities of Acanthopeltis japonica Okamura and Yatabella hirsuta Okamura were determined from nucleotide sequences of the nuclear-encoded small subunit rDNA (SSU), internal transcribed spacer 1 (ITS1), and plastid-encoded large subunit of the ribulose-1,5-bisphosphate carboxylase/oxgenase gene (rbcL). We have sequenced an additional nine species of Japanese gelidialean species. Although Acanthopeltis and Yatabella had been suggested to be derived from separate lineages by researchers who emphasized the difference of growth pattern, they were recognized as a monophyletic group in the SSU, ITS1, and rbcL analyses. We have also demonstrated that Acanthopeltis and Yatabella possess a fundamentally similar type of growth pattern. The molecular data and morphological similarities indicate that Acanthopeltis and Yatabella are congeneric. The new combination, Acanthopeltis hirsuta (Okamura) Shimada, Horiguchi et Masuda, comb. nov., is proposed. Additional information on phylogenetic relationships within the Gelidiales was obtained. Our phylogenetic analyses of the Gelidiales using the above genes show three major clades, the Gelidiella clade that was the earliest diverging group within the order, a Pterocladia/Pterocladiella clade, and a large Gelidium-complex clade. The large Gelidium-complex clade is composed of the Ptilophora clade, Capreolia clade, and Gelidium-complex clades. In the rbcL and ITS1 trees, the Gelidium-complex clade includes three subclades, one of which is recognized for the first time and includes Acanthopeltis/Yatabella, Onikusa japonica (Harvey) Akatsuka, and Gelidium vagum Okamura, all distributed in the western and eastern Pacific. The type of secondary rhizoidal attachment, the unicellular independent type, peg type, and brush type, is consistent with the respective three major clades of the Gelidiales, suggesting that this morphological character reflects the phylogeny of this order