Assortative mating can help adaptation of flowering time to a changing climate: insights from a polygenic model

Several empirical studies report fast evolutionary changes in flowering time in response to contemporary climate change. Flowering time is a polygenic trait under assortative mating, since flowering time of mates must overlap. Here we test whether assortative mating, compared to random mating, can help better track a changing climate. For each mating pattern, our individual-based model simulates a population evolving in a climate characterized by stabilizing selection around an optimal flowering time, which can change directionally and/or fluctuate. We also derive new analytical predictions from a quantitative genetics model for the expected genetic variance at equilibrium, and its components, the lag of the population to the optimum, and the population mean fitness. We compare these predictions between assortative and random mating, and to our simulation results. Assortative mating, compared to random mating, has antagonistic effects on genetic variance: it generates positive associati...