Meeting Abstract
The majority of modern day animal species have separate sexes (gonochorism). However, the ancestral sexual condition (gonochorism or hermaphroditism) is unresolved. Controversies surrounding the relationships of the five major animal lineages (i.e., Bilateria, Cnidaria, Ctenophora, Placozoa, and Porifera) complicate this question. In this study, we reconstruct ancestral sexual conditions of key animal nodes using multiple starting topologies and multiple approaches. We find that the last common ancestor of all animals was most likely a simultaneous hermaphrodite regardless of whether the starting topology has ctenophores or sponges as the sister group to the rest of animals. Furthermore, we find it highly probable that last common ancestor of Cnidaria and Bilateria was gonochoristic. This work establishes the sexual condition of key nodes in animal history and therefore establishes the timing of events that led to major transitions. These data will provide the groundwork necessary for understanding the mechanisms surrounding these transitions, which undoubtedly contributed to some of the most impressive and elaborate morphological traits in the animal kingdom.
