Two lineages within Griffithsia (Ceramiaceae, Rhodophyta) based on plastid protein-coding psaA, psbA and rbcL genes

The ceramiaceous red algal genus Griffithsia C. Agardh includes about 27 species that are distributed along tropical to temperate coasts. Although Griffithsia has been subdivided into four groups based on morphology, there are no attempts on molecular phylogeny of the genus. Sequences of psaA, psbA, and rbcL, protein-coding genes in plastid, were analyzed for nine samples of seven Griffithsia species, 11 samples of four putative relatives such as Anotrichium Naegeli and Halurus Kuetzing, and three outgroup taxa. Although sequence divergences for psaA and rbcL were higher than those for psbA, the saturation plots for each of psaA, psbA, and rbcL data showed no evidence of saturation at 1st, 2nd, and 3rd codon position. Partition homogeneity test also indicated that psaA, psbA, and rbcL sequences did not result in significantly incongruent trees. Analyses of separate and concatenated data sets indicated that Griffithsia formed two well-supported clades: one lineage including C. corallinoides, G. pacifica, and G. tomo-yamadae, and the other lineage having G. antarctica. G. japonica; G. teges, and G. traversii. Our study indicates that psaA and psbA genes as well as rbcL are suitable tools for phylogenetic investigations of the genus Griffithsia.