Meeting Abstract
There is significant disagreement on the phylogenetic relationships at the root of the animal tree of life. While initial analyses of genomic-scale datasets associated with the publication of the first two, completely sequenced, comb jellies (phylum Ctenophora) genomes (Ryan et al. 2013; Moroz et al. 2014; and Whelan et al. 2015) suggested that this lineage might represent the sister group of all the other animals, further re-analyses of the datasets associated with these studies (Pisani et al. 2015) showed that a position of the ctenophores at the root of the animal tree is most likely a tree reconstruction artifact. The results of Pisani and collaborators sparked a heated debate (e.g. Halanych et al. 2016 Vs Pisani et al. 2016) with Halanych et al. (2016) suggesting that, contrary to Pisani et al. (2015), the placement of the sponges at the root of the animal tree might represent a compositional attraction between Silicean sponges and the outgroups. Here, we will present results of reanalyses of all recently published datasets (Whelan et al. 2015; Chang et al. 2015; Cannon et al. 2016; Zapata et al. 2016) that bears on this problem and show that contrary to Halanych et al. (2016) correcting for compositional heterogeneity invariably strengthen support for sponges as the sister group of all the other animals. This strongly confirms the results of Pisani et al. (2015), and illustrate the pitfalls associated with the use of models (like the simple GTR+G, or multiple GTR+G) that do not account for all forms of heterogeneity in the data.
