Molecular phylogeny of Phyllariaceae, Halosiphonaceae and Tilopteridales (Phaeophyceae)

Phylogenetic relationships of problematic members of the Laminariales (Halo siphon and Phyllariaceae) and Tilopteridales were studied comparing Rubisco gene (rbcL and spacer) and ribosomal DNA (5.8S, ITS2 and a part of 26S) se quence 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 wit h the Phyllariaceae and Halosiphon, contrary to conventional taxonomy on th e basis of life history patterns and morphological features. Halosiphon, Ph yllariaceae 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 cla de, including all the taxa mentioned above, formed a sister lineage to a gr oup including Akkesiphycus, Pseudochordaceae, Chordaceae and the 'advanced' Laminariales (Alariaceae, Laminariaceae and Lessoniaceae). The rbcL + Rubi sco spacer sequences, as well as the 5.8S + ITS2 + 26S rDNA sequences, supp orted the independence of existing taxa of the Phyllariaceae and suggested early divergence of Saccorhiza within the family.