S8-2.3 Sunday, Jan. 6 Phylogenomics of non-bilaterian animals: pitfalls and challenges WOERHEIDE, G; Ludwig-Maximilians-Universitaet Muenchen email@example.com
Deep-level metazoan relationships have long been controversial issues. Especially a well resolved and supported phylogeny of non-bilaterian animals is needed to provide a robust framework for reconstructing early metazoan evolution. Expanding molecular (phylogenomic) datasets are increasingly being used to unravel these relationships. However, important nodes remain notoriously difficult to resolve. For example, some recent large-scale metazoan phylogenomic analyses – contrary to classical conceptions – found ctenophores to be the sister-group to the remaining Metazoa and favored a sister-group relationship between sponges and cnidarians, while other analyses suggest that the Placozoa are the sister-group to the remaining Metazoa or that sponges are a paraphyletic assemblage that share a grade of construction rather than common ancestry. From these hypotheses, many claims have been made with far reaching implications for the early evolution of animals. An overview about the current state of the debate will be given, especially with respect to the mono- vs. paraphyly of sponges and their position in the animal tree of life. Several (novel) phylogenomic analyses of non-bilaterians will be used to address the underlying causes of the incongruences observed among deep-level metazoan phylogenies. However, even using large phylogenomic datasets, some non-bilaterian relationships remain difficult to resolve as they are highly dependent on taxon- and gene sampling, evolutionary model selection and outgroup choice. Additional sequence-independent data might be required to unequivocally resolve the branching order of all non-bilaterian groups.