Can Population Genetics Adapt to Rapid Evolution?

Population genetics largely rests on a ‘standard model’ in which random genetic drift is the dominant force, selective sweeps occur infrequently, and deleterious mutations are purged from the population by purifying selection. Studies of phenotypic evolution in nature reveal a very different picture, with strong selection and rapid heritable trait changes being common. The time-rate scaling of phenotypic evolution suggests that selection on phenotypes is often fluctuating in direction, allowing phenotypes to respond rapidly to environmental fluctuations while remaining within relatively constant bounds over longer periods. Whether such rapid phenotypic evolution undermines the standard model will depend on how many genomic loci typically contribute to strongly selected traits and how phenotypic evolution impacts the dynamics of genetic variation in a population. Population-level sequencing will allow us to dissect the genetic basis of phenotypic evolution and study the evolutionary dynamics of genetic variation through direct measurement of polymorphism trajectories over time.

TrendsStudies of evolution in action show that phenotypic traits can often change dramatically over the course of just a few generations.This differs markedly from the paradigm of slow molecular evolution commonly adopted in our population genetic models.To assess whether our models are still appropriate, we need to better understand how rapid phenotypic evolution impacts the trajectories of genetic variation in a population.New population genomic datasets will make it possible to directly observe how polymorphism frequencies change in a population over time, allowing us to test and refine our population genetic models.