Meeting Abstract
Ctenophora is the sister group to all other extant animals. However, relationships among ctenophore lineages are poorly understood. In particular, only limited molecular phylogenetic studies on ctenophores have been conducted. Furthermore, these studies conflict with morphology-based hypotheses, especially in regards to the placement of species lacking tentacles. Robustly resolving relationships among ctenophore lineages will be essential for understanding the evolution of ctenophore body plans. We sequenced 16 new ctenophore transcriptomes and combined these with ten publicly available ctenophore transcriptomes to assemble a phylogenomic dataset of Ctenophora. Orthology determination resulted in a primary data set of 306 genes and over 80,000 amino acid positions. Maximum likelihood analyses on a partitioned dataset using RAxML recovered a well-supported phylogeny. In agreement with recent phylogenetic hypotheses, two higher-level Ctenophora groupings, Lobata and Cydippida, were recovered non-monophyletic. Euplokamis, rather than atentaculate beroids, were recovered sister to all other extant ctenophores, supporting previous genetic evidence that atentaculate ctenophores are derived. Atentaculate species included here formed a monophyletic derived clade. Benthic species in the order Platyctenida (i.e. Coeloplana, Vallicula) were monophyletic. The enigmatic, semi-benthic species Lobatolampea tetragona was recovered at the base of a clade containing Ocyropsis, Cestum, and Bolinopsidae spp. The transcriptomic-based approach used here has resulted in a robust picture of ctenophore relationships, and our findings indicate that the traditional higher-level classifications should be revised.
