ORAL PRESENTATION: A theoretical study of the effects of assortative mating on the adaptive potential under climate change

Submitted by : Fady Bruno
Abstract type : Oral presentation
Session type : Conference session 2: LOCAL ADAPTATION of CLIMATE CHANGE-RELATED TRAITS
Author Speaker : Claire Godineau

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Co-authors : Ophélie Ronce and Céline Devaux.

Author affiliation : Institut des Sciences de l'Évolution, Université de Montpellier, CNRS, IRD, EPHE Montpellier, France.

Abstract :

Rapid evolutionary responses to contemporary climate change have been measured mostly for phenological traits, especially flowering times. Flowering times of mates have to be similar for reproduction to take place, and are thus under assortative mating. Compared to random mating, assortative mating is predicted to increase the genetic variance of polygenic traits at mutation-genetic drift equilibrium, and to increase evolutionary response to directional selection. We lack quantitative predictions about the effect of assortative mating on adaptive potential under scenarios of selection that mimic climate change. We here built an individual-based quantitative genetics model to compare the adaptive potential of a polygenic trait under random versus assortative mating. We analyzed equilibrium genetic variance and mean population fitness for several selection regimes defined by intermediate to strong stabilizing selection, combined with a constant moving optimum and inter-generational fluctuations of the optimum. For a stationary environment with uncorrelated fluctuations and moderate to strong selection, assortative mating does not facilitate adaptation of populations compared to random mating. In contrast, when the optimum changes directionally with fluctuations around this trend, thus mimicking climate change, assortative mating increases genetic variance, which decreases the lag to the optimum and increases mean population fitness. The fitness advantage of assortative mating increases with the speed of change of the optimum. Comparison to analytical predictions shows that the adaptive advantage of assortative mating is entirely explained by the evolution of larger genetic variances. The fitness advantage of assortative mating decreases when the genetic variance becomes less limiting for adaptation, e.g. when the number of loci or the intensity of stabilizing selection increases. Therefore, in the context of climate change, assortative mating should allow better tracking of changing environments than should random mating and may contribute to rapid evolution of phenological traits.

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Keywords : quantitative genetics, genetic adaptation to climate change, assortative mating, flowering time