Morphological innovation and developmental genetics

How do the actions of individual genes contribute to the complex morphologi es of animals and plants? How widespread are these genes taxonomically? How many genes are involved in the morphological differences observed between species, and can we identify them? To what extent can empirical data and th eory be reconciled? We provide an overview of some recent attempts to answe r these questions, answers that have taken us to the threshold of understan ding the mechanistic basis and evolutionary factors that underlie morpholog ical innovation.