Abstract
The evolutionary diversification of animals is one of nature’s greatest mysteries. In addition, animals evolved wildly divergent multicellular life strategies featuring ciliated sensory epithelia. In many lineages epithelial sensoria became coupled to increasingly complex nervous systems. Currently, different phylogenetic analyses of single-copy genes support mutually-exclusive possibilities that either Porifera or Ctenophora is sister to all other animals. Resolving this dilemma would advance the ecological and evolutionary understanding of the first animals. Here we computationally identify and analyze gene families with ancient duplications that could be informative. In the TMC family of mechano-transducing transmembrane channels, we find that eumetazoans are composed of Placozoa, Cnidaria, and Bilateria, excluding Ctenophora. Likewise, in the MLX/MLXIP family of bHLH-ZIP regulators of metabolism, we find that members of a proposed clade of “Benthozoa” (Porifera + Eumetazoa) share a duplication, absent in Ctenophora. These results suggest a new avenue for deducing deep phylogeny by choosing rather than avoiding ancient gene paralogies.
