Developmental characters in phylogenetic inference and their absolute timing information.

Despite the recent surge of interest in studying the evolution of development, surprisingly little work has been done to investigate the phylogenetic signal in developmental characters. Yet, both the potential usefulness of developmental characters in phylogenetic reconstruction and the validity of inferences on the evolution of developmental characters depend on the presence of such a phylogenetic signal and on the ability of our coding scheme to capture it. In a recent study, we showed, using simulations, that a new method (called the continuous analysis) using standardized time or ontogenetic sequence data and squared-change parsimony outperformed event pairing and event cracking in analyzing developmental data on a reference phylogeny. Using the same simulated data, we demonstrate that all these coding methods (event pairing and standardized time or ontogenetic sequence data) can be used to produce phylogenetically informative data. Despite some dependence between characters (the position of an event in an ontogenetic sequence is not independent of the position of other events in the same sequence), parsimony analysis of such characters converges on the correct phylogeny as the amount of data increases. In this context, the new coding method (developed for the continuous analysis) outperforms event pairing; it recovers a lower proportion of incorrect clades. This study thus validates the use of ontogenetic data in phylogenetic inference and presents a simple coding scheme that can extract a reliable phylogenetic signal from these data.