Meeting Abstract

P1.127  Jan. 4  A Molecular Phylogenetic Analysis of Octocorallia Using Complete Large Subunit Ribosomal DNA MCFADDEN, C.S.*; WALSH, K.M.; Harvey Mudd College mcfadden@hmc.edu

The anthozoan sub-class Octocorallia includes over 3000 species of soft corals, sea fans and sea pens. At present the sub-class is divided into three orders (Pennatulacea, Helioporacea and Alcyonacea); the large O. Alcyonacea (29 families of sea fans and soft corals) is further subdivided into six sub-ordinal groups on the basis of colony architecture and skeletal composition. In contrast to this traditional taxonomic classification, recent molecular phylogenies constructed using both 18S rDNA and mitochondrial protein-coding genes support two distinct clades of Octocorallia, one that unites the sea pens (O. Pennatulacea) with the sea fan sub-order Calcaxonia, and a second that includes representatives of the other five sub-ordinal groups of Alcyonacea. All of the molecular studies published so far, however, suffer from poor phylogenetic resolution of the deeper nodes within the tree, and the root of Octocorallia has not yet been determined with any certainty. We have sequenced nearly complete 28S rDNA (~3500 bp) for approximately 20 octocoral taxa representing all of the major groups. Our preliminary phylogenetic analyses suggest that this large nuclear gene, in combination with other markers, will provide increased resolution of basal nodes and allow us to root the Octocorallia with respect to other cnidarians.