Meeting Abstract
The branching pattern at the base of the metazoan phylogeny has been a long-standing, unanswered question that must be resolved before issues concerning the transition from unicellularity to multicellularity can be appropriately addressed. Numerous studies have attempted to resolve the relative position of Ctenophora, Porifera, Placozoa, Cnidaria, and Bilataria, but the results of these studies have been alternative hypotheses that fail to fully clarify metazoan phylogeny. Recent advances in sequencing technologies can be employed to compile a phylogenomic dataset with more complete character matrices and greater outgroup, Ctenophora, Porifera, and Cnidarian taxon sampling than employed in previous studies. Despite technological advances, there are still limits to the amount of overlap that can be expected concerning which genes are sequenced for each taxon. Therefore, we discuss a bioinformatics pipeline that emphasizes quality of data to ensure accurate orthology determination. Such a pipeline also works to limit the amount of missing data in the overall data matrix with the goal of reducing phylogenetic inference artifacts. New methods for model testing can also be employed to find best fit amino acid substitution models and data partitioning schemes. Using this approach, a Maximum Likelihood phylogenetic reconstruction resolved Ctenophora as the most basal metazoan lineage with 100% bootstrap support for all major nodes. Hypotheses inferred with different datasets, Maximum Likelihood analysis, traditional Bayesian phylogenetics, and Bayesian concordance analysis will be compared in an effort to highlight best practices for resolving deep nodes in the tree of life.
