Phylogenetic relationships within the Fucales (Phaeophyceae) assessed by the photosystem I coding <i>psa</i> A sequences

Abstract

G.Y. Cho, F. Rousseau, B. de Reviers and S.M. Boo. 2006. Phylogenetic relationships within the Fucales (Phaeophyceae) assessed by the photosystem I coding psaA sequences. Phycologia 45: 512–519. DOI: 10.2216/05-48.1Fucalean brown algae are ecologically important for maintaining intertidal to subtidal ecosystems and are currently a subject for DNA phylogenies. We analyzed the photosystem I coding psaA gene (1488 base pairs) from 26 taxa in all families of the Fucales including Nemoderma tingitanum and Microzonia velutina as outgroup species. A total of 41 taxa, including published sequences from three fucalean and 13 brown algae, were used for phylogenetic analyses. The psaA phylogenies confirmed previous ideas, based on previous studies using morphology and nuclear ribosomal genes, suggesting that the fucalean algae are monophyletic, including the Durvillaeaceae and Notheiaceae. However, in all analyses of the psaA data, the Notheiaceae, endemic to Australasia, occupied a basal position within the order. All families except the Cystoseiraceae are monophyletic. The psaA data together with previous nuclear ribosomal DNA data and autapomorphic morphological characters strongly support that the genera Bifurcariopsis and Xiphophora should be separated from the Cystoseiraceae and the Fucaceae, respectively. Two new families, Bifurcariopsidaceae and Xiphophoraceae, are proposed to accommodate each of the genera. The psaA data concur with the morphological and biogeographical hypotheses that fucalean algae might have originated from Australasian waters and have become established in the northern hemisphere. The present results indicate that the psaA region is a new tool for better understanding phylogenetic relationships within fucalean algae.