title: Catch Me if You Can: Adaptation from Standing Genetic Variation to a Moving Phenotypic Optimum.
abstract: Adaptation lies at the heart of Darwinian evolution. Accordingly, numerous studies have tried to provide a formal framework for the description of the adaptive process. Of these, two complementary modeling approaches have emerged: While so-called adaptive-walk models consider adaptation from the successive fixation of de novo mutations only, quantitative genetic models assume that adaptation proceeds exclusively from preexisting standing genetic variation. The latter approach, however, has focused on short-term evolution of population means and variances rather than on the statistical properties of adaptive substitutions. Our aim is to combine these two approaches by describing the ecological and genetic factors that determine the genetic basis of adaptation from standing genetic variation in terms of the effect-size distribution of individual alleles. Specifically, we consider the evolution of a quantitative trait to a gradually changing environment. By means of analytical approximations, we derive the distribution of adaptive substitutions from standing genetic variation, that is, the distribution of the phenotypic effects of those alleles from the standing variation that become fixed during adaptation. Our results are checked against individual-based simulations. We find that, compared to adaptation from de novo mutations, (i) adaptation from standing variation proceeds by the fixation of more alleles of small effect and (ii) populations that adapt from standing genetic variation can traverse larger distances in phenotype space and, thus, have a higher potential for adaptation if the rate of environmental change is fast rather than slow.
authors.affiliation: Mathematics and BioSciences Group, Faculty of Mathematics, University of Vienna, A-1090 Vienna, Austria sebastian.matuszewski@epfl.ch.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Matuszewski
authors.affiliation: Mathematics and BioSciences Group, Faculty of Mathematics, University of Vienna, A-1090 Vienna, Austria Max F. Perutz Laboratories, A-1030 Vienna, Austria.
authors.forename: Joachim
authors.initials: J
authors.lastname: Hermisson
authors.affiliation: Aix Marseille Université, Centre National de la Recherche Scientifique, Centrale Marseille, I2M, Unité Mixte de Recherche 7373, 13453 Marseille, France.
authors.forename: Michael
authors.initials: M
authors.lastname: Kopp
mesh_terms: D000222:Adaptation, Physiological; D000483:Alleles; D004777:Environment; D019143:Evolution, Molecular; D014644:Genetic Variation; D008957:Models, Genetic; D009154:Mutation; D010641:Phenotype; D011336:Probability
keywords: adaptation; models/simulations; natural selection; population genetics; standing genetic variation