DOES DEVELOPMENTAL INFORMATION ADD PHYLOGENETIC SIGNAL?

Advances in developmental evolutionary biology have greatly increased our understanding of how morphological features are constructed and how development shapes their change through time. It is now clear that developmental gene regulatory networks are highly conserved and often rigidly associated with particular morphologies. The complex wiring of these networks imposes lineage-specific constraints upon rates and patterns of morphological character evolution. Because morphology, whether fossil or recent, is the outcome of developmental process, basic principles from living systems may be used to help constrain fossil phylogenies. To explore the usefulness and contribution of developmental information to phylogenetic analyses, I applied a Bayesian phylogenetic approach to existing morphological datasets, including those from a problematic and character-depauperate group, the lobopods. Lobopods are currently thought to represent a basal grade leading to extant onychophorans and arthropods, but the phylogenetic relationship among fossil lineages is difficult to decipher on fossil morphology alone. I compared models designed to accommodate variation in evolutionary rate, both among characters and among (defined a priori) developmental character partitions, as well as asymmetric character transitions to determine if incorporating developmental information can better inform phylogenetic hypotheses.