Meeting Abstract

26.3  Wednesday, Jan. 5  Phylogenomics of Hemichordata within Deuterostomia CANNON, Johanna T*; KOCOT, Kevin M; SANTOS, Scott R; SWALLA, Billie J; HALANYCH, Kenneth M; Auburn University; Auburn University; Auburn University; University of Washington; Auburn University cannojt@auburn.edu

Hemichordates are of particular interest to studies of early chordate and deuterostome evolution due to several shared morphological features. Despite their evolutionary significance, relationships within Hemichordata remain poorly understood. The two traditional classes within Hemichordata are Enteropneusta, or acorn worms, and Pterobranchia, which are tiny, colonial animals. Elucidating relationships between these forms has consequences not only for our understanding of the last common ancestor of hemichordates, but also ancestors of chordates and all deuterostomes. Molecular phylogenetic studies using nuclear 18S rDNA have indicated that pterobranchs may have originated from within Enteropneusta. To further investigate pterobranch placement, we have taken a phylogenomic approach using transcriptome and genome data. To this end, we generated transcriptome data from four hemichordate species (two pterobranchs and two enteropneusts) using Roche 454 pyrosequencing technology. Using a custom bioinformatics pipeline, these data were combined with deuterostome and outgroup sequences from publicly available sources. Existing bioinformatics tools were used to streamline orthology determination and gene selection. Alignments including up to 700+ genes and 35 deuterostome taxa were generated. Contrary to 18S rDNA results, preliminary phylogenetic analyses placed pterobranchs as sister group to monophyletic enteropneusts. This result is consistent with traditional views of hemichordate evolution, and may help us reconstruct deuterostome ancestral forms. Implications for hemichordate evolution, as well as dataset assembly methods for phylogenomics, will be discussed.