Molecular Phylogeny of Lophotrochozoa Based on 18S rRNA Gens Sequences-with Comment on the Phylogenetic Position of Bryozoa

Abstract

Lophotrochozoa relationships were examined based on 18S rDNA evidence. The complete 18S rRNA genes of eight species of cheilostome bryozoans commonly found in coastal waters of China were amplified through polymerase chain reaction (PCR) and sequenced. Combined with known sequences of other bryozoans and related lophotrochozoans available through GenBank, Hydra littoralis as an outgroup, the molecular phylogenetic trees of Lophotrochozoa were reconstructed using the neighbour joining (NJ) and maximum parsimony methods in PHYLIP software. The results show, Gnathostomulida, Gastrostricha, Rotifera, Acanthocephala and Platyhelminthes constitute the basal branches of the phylogentic trees;Bryozoa appears to be polyphyletic within a monophyletic clade including other lophotrochozoan phyla. We also briefly discuss the phylogenetic relationships among the lophotrochozoan phyla and evaluated the phylogenetic position of Bryozoa in the light of this molecular and morphological evidence.