Phylogeny of the Northeast Pacific brown algal (Phaeophycean) orders as inferred from 18S rRNA gene sequences

Partial 18S rRNA gene sequences have been determined for thirteen brown algae representing nine Northeast Pacific brown algal orders: Chordariales, Desmarestiales, Dictyosiphonales, Dictyotales, Ectocarpales, Fucales, Scytosiphonales, Sphacelariales and Syringodermatales. These sequences were compared with published sequences from a kelp (Laminariales), a xanthophyte and a bacillariophyte. A preliminary phylogeny generated by the neighbor-joining phylogeny inference method indicated that the class Phaeophyceae is a monophyletic group in relation to the xanthophyte and the bacillariophyte. Further, bootstrap analysis of the phylogeny consistently grouped together all the representatives belonging to the orders Ectocarpales, Chordariales, Dictyosiphonales and Scytosiphonales and separated them from the representatives belonging to the other brown algal orders. These results offer valuable insights into the controversial brown algal orders' phylogeny and provide additional data to the phylogenetic relationship study among the chromophyte classes.