PHYLOGENETIC AND MECHANISTIC ANALYSIS OF A DEVELOPMENTALLY INTEGRATEDCHARACTER COMPLEX - ALTERNATE LIFE-HISTORY MODES IN AMBYSTOMATID SALAMANDERS

Many of the critical pieces are now in place to exploit the evolution of paedomorphosis (metamorphic failure) as a model for both the phylog enetic and mechanistic analysis of a developmentally integrated charac ter. Phylogenetic analyses indicate that paedomorphosis has evolved co nvergently among different populations and species of ambystomatids du ring the recent past. Mechanistically, there is growing evidence that paedomorphosis is controlled by a few loci, with different combination s of loci and alleles blocking metamorphosis in different conspecific populations and among closely related species. A reductionistic approa ch is needed to determine if the same or different loci were altered i n the independent evolution of paedomorphosis among different ambystom atid lineages. We provide an overview of the genetic strategies that w e are using toward this end, and present some of our own published and unpublished results. We then briefly discuss the potential insights a nd limitations of the reductionistic approach to character evolution t hat we are advocating in this research strategy.