Eric C. Henry

Molecular phylogeny of Phyllariaceae , Halosiphonacea e and Tilopteridales (Phaeophyceae)

Abstract Phylogenetic relationships of problematic members of the Laminariales (Halosiphon and Phyllariaceae) and Tilopteridales were studied comparing Rubisco gene (rbcL and spacer) and ribosomal DNA (5.8S, ITS2 and a part of 26S) sequence data covering all species of these taxa and ‘primitive’ Laminariales. Molecular phylogenetic trees were constructed by use of maximum parsimony (MP), maximum likelihood (ML) and neighbour-joining (NJ) methods. The rbcL data supported a monophyletic Tilopteridales and its close affiliation with the Phyllariaceae and Halosiphon, contrary to conventional taxonomy on the basis of life history patterns and morphological features. Halosiphon, Phyllariaceae and Tilopteridales formed a sister group to a clade consisting of Desmarestiales and Sporochnales in the ML and NJ analyses, although the bootstrap values supporting the relationship were not high. This larger clade, including all the taxa mentioned above, formed a sister lineage to a group including Akkesiphycus, Pseudochordaceae, Chordaceae and the ‘advanced’ Laminariales (Alariaceae, Laminariaceae and Lessoniaceae). The rbcL + Rubisco spacer sequences, as well as the 5.8S + ITS2 + 26S rDNA sequences, supported the independence of existing taxa of the Phyllariaceae and suggested early divergence of Saccorhiza within the family.