Taxonomic placement of Microzonia (Phaeophyceae) in the Syringodermatales based on the rbcL and 28S nrDNA sequences

The position of the brown algal genus Microzonia, currently placed in the Cutleriales, was investigated using two different genes: the plastid-encoded rbcL gene and the nuclear-encoded rDNA 28S gene. All our analyses show that Microzonia is the sister taxon of Syringoderma and is not related to the cutlerialean genera Cutleria and Zanardinia. This result is consistent with morphological characters. It is thus proposed to exclude Microzonia from the Cutleriales and to place it in the Syringodermatales. Within the Phaeophyceae, the Syringoderma-Microzonia branch diverges after Choristocarpus and members of the Dictyotales and the Sphacelariales, as the sister taxon of a clade comprising all other orders. The extreme basal position of Choristocarpus is confirmed with both rbcL and 28S genes, contrary to previous reports by other authors.