Quantifying the impact of development on phenotypic variation and evolution.

A primary goal of evolutionary biology is to identify the factors that shape phenotypic evolution. According to the theory of natural selection, phenotypic evolution occurs through the differential survival and reproduction of individuals whose traits are selectively advantageous relative to other individuals in the population. This implies that evolution by natural selection is contingent upon the distribution and magnitude of phenotypic variation among individuals, which are in turn the products of developmental processes. Development therefore has the potential to affect the trajectory and rate of phenotypic evolution. Recent research in diverse systems (e.g., mammalian teeth, cichlid skulls, butterfly wings, and marsupial limbs) supports the hypothesis that development biases phenotypic variation and evolution, but suggests that these biases might be system-specific.