Phylogenetic and mechanistic analysis of a developmentally integrated character complex: Alternate life history modes in ambystomatid salamanders

SYNOPSIS. Many of the critical pieces are now in place to exploit the evolution of paedomorphosis (metamorphic failure) as a model for both the phylogenetic and mechanistic analysis of a developmentally integrated character. Phylogenetic analyses indicate that paedomorphosis has evolved convergently among different populations and species of ambystomatids during the recent past. Mechanistically, there is growing evidence that paedomorphosis is controlled by a few loci, with different combinations of loci and alleles blocking metamorphosis in different conspecific populations and among closely related species. A reductionistic approach is needed to determine if the same or different loci were altered in the independent evolution of paedomorphosis among different ambystomatid lineages. We provide an overview of the genetic strategies that we are using toward this end, and present some of our own published and unpublished results. We then briefly discuss the potential insights and limitations of the reductionistic approach to character evolution that we are advocating in this research strategy.