PASSAMANECK, Y. J.; HALANYCH, K. M.; Woods Hole Oceanographic Institution; Woods Hole Oceanographic Institution: Bryozoan affinities accessed using Hox genes and ribosomal RNA genes

The phylogentic position of the Bryozoa represents an ongoing question in the study of metazoan evolution. Various interpretations of morphological and developmental features have posited a close relationship to either protostomes or deuterostomes, as well as an intermediate position between the two groups. Molecular phylogenetic analyses of 18S ribosomal RNA gene sequences have suggested the Byrozoa to be members of a protostome radiation, as have recent cladistic analyses of morphological characters. Bryozoans have traditionally been viewed as closely related to brachiopods and phoronids, together termed the Lophophorata in reference to a similar ciliated feeding structure in the three groups. However, recent analyses have failed to support the monophyly of the Lophophorata. The present study utilizes Hox gene sequences, as well as 18S and 28S ribosomal RNA genes, to explore the phylogentic affinities of the Bryozoa. The independent duplications of Hox genes in the Lophotrochozoa, Ecdysozoa, and Deuterostomia has resulted in clade specific orthologs characterized by unique peptide motifs. Hox genes appear to be useful in resolving phylogenetic relationships, and may be less susceptible to artifacts of long-branch attraction than are ribosomal genes, which display high levels of rate variation between lineages.