• PNAS Alerting Services
  • Sign-up for PNAS eTOC Alerts

Seasonally fluctuating selection can maintain polymorphism at many loci via segregation lift

  1. Dmitri A. Petrova,1
  1. aDepartment of Biology, Stanford University, Stanford, CA 94305;
  2. bFakult?t für Mathematik, Universit?t Wien, 1090 Wien, Austria;
  3. cFakult?t für Biologie, Universit?t Bielefeld, 33615 Bielefeld, Germany;
  4. dDepartment of Biology, University of Virginia, Charlottesville, VA 22904;
  5. eDepartment of Biology, University of Pennsylvania, Philadelphia, PA 19104-6313
  1. Edited by M. T. Clegg, University of California, Irvine, CA, and approved October 3, 2017 (received for review March 8, 2017)


A key question in evolutionary biology is: What maintains the abundant genetic variation observed in natural populations? Many organisms experience some seasonality in their habitats, and, if they have multiple generations per year, seasonally fluctuating selection is a potentially powerful mechanism to maintain polymorphism. However, previous research has argued that this occurs rarely. Inspired by recent empirical findings, we reevaluate the potential of seasonally fluctuating selection to simultaneously maintain polymorphism at many loci in the genome. We obtain a more general condition for the maintenance of multilocus polymorphism by seasonally fluctuating selection. This condition may plausibly be satisfied for many species and does not suffer from problems of previous models.


Most natural populations are affected by seasonal changes in temperature, rainfall, or resource availability. Seasonally fluctuating selection could potentially make a large contribution to maintaining genetic polymorphism in populations. However, previous theory suggests that the conditions for multilocus polymorphism are restrictive. Here, we explore a more general class of models with multilocus seasonally fluctuating selection in diploids. In these models, the multilocus genotype is mapped to fitness in two steps. The first mapping is additive across loci and accounts for the relative contributions of heterozygous and homozygous loci—that is, dominance. The second step uses a nonlinear fitness function to account for the strength of selection and epistasis. Using mathematical analysis and individual-based simulations, we show that stable polymorphism at many loci is possible if currently favored alleles are sufficiently dominant. This general mechanism, which we call “segregation lift,” requires seasonal changes in dominance, a phenomenon that may arise naturally in situations with antagonistic pleiotropy and seasonal changes in the relative importance of traits for fitness. Segregation lift works best under diminishing-returns epistasis, is not affected by problems of genetic load, and is robust to differences in parameters across loci and seasons. Under segregation lift, loci can exhibit conspicuous seasonal allele-frequency fluctuations, but often fluctuations may be small and hard to detect. An important direction for future work is to formally test for segregation lift in empirical data and to quantify its contribution to maintaining genetic variation in natural populations.


  • ?1To whom correspondence may be addressed. Email: meike.wittmann{at}uni-bielefeld.de or dpetrov{at}stanford.edu.
  • Author contributions: M.J.W., A.O.B., M.W.F., P.S.S., and D.A.P. designed research; M.J.W. performed analyses and simulations; A.O.B., M.W.F., and D.A.P. gave input on all aspects of the analyses; P.S.S. gave input on the paper; and M.J.W, A.O.B., M.W.F., and D.A.P. wrote the paper.

  • The authors declare no conflict of interest.

  • This article is a PNAS Direct Submission.

  • Data deposition: Source code underlying the analyses in this manuscript has been deposited in the figshare repository (available at http://www.danielhellerman.com/10.6084/m9.figshare.5142262).

  • This article contains supporting information online at www.danielhellerman.com/lookup/suppl/doi:10.1073/pnas.1702994114/-/DCSupplemental.

Published under the PNAS license.

Online Impact

    <var id="UPyyYwe"><strike id="UPyyYwe"></strike></var>
    <ins id="UPyyYwe"></ins>
    <ins id="UPyyYwe"></ins>
    <cite id="UPyyYwe"><video id="UPyyYwe"></video></cite>
    <ins id="UPyyYwe"></ins><ins id="UPyyYwe"><span id="UPyyYwe"><cite id="UPyyYwe"></cite></span></ins>
    <var id="UPyyYwe"><span id="UPyyYwe"></span></var>
    <cite id="UPyyYwe"><video id="UPyyYwe"><var id="UPyyYwe"></var></video></cite>
    <cite id="UPyyYwe"></cite>
    <var id="UPyyYwe"></var>
    <cite id="UPyyYwe"></cite>
    <ins id="UPyyYwe"></ins>
    <cite id="UPyyYwe"><span id="UPyyYwe"></span></cite><cite id="UPyyYwe"></cite>
    <var id="UPyyYwe"><video id="UPyyYwe"><menuitem id="UPyyYwe"></menuitem></video></var>
    <var id="UPyyYwe"><span id="UPyyYwe"></span></var>
    <ins id="UPyyYwe"></ins>
    <ins id="UPyyYwe"></ins><var id="UPyyYwe"><span id="UPyyYwe"></span></var>
    <var id="UPyyYwe"><span id="UPyyYwe"></span></var>
    <cite id="UPyyYwe"></cite>
    <var id="UPyyYwe"><strike id="UPyyYwe"><menuitem id="UPyyYwe"></menuitem></strike></var>
    <ins id="UPyyYwe"></ins>
    <cite id="UPyyYwe"></cite><cite id="UPyyYwe"></cite>
  • 8686301327 2018-02-22
  • 1879481326 2018-02-22
  • 9332351325 2018-02-22
  • 7384141324 2018-02-22
  • 8918371323 2018-02-22
  • 7638311322 2018-02-22
  • 9654151321 2018-02-22
  • 1588961320 2018-02-22
  • 5712971319 2018-02-22
  • 5536211318 2018-02-22
  • 4417061317 2018-02-22
  • 3024201316 2018-02-21
  • 4658931315 2018-02-21
  • 3216561314 2018-02-21
  • 1965251313 2018-02-21
  • 970811312 2018-02-21
  • 609011311 2018-02-21
  • 3219131310 2018-02-21
  • 613261309 2018-02-21
  • 6972481308 2018-02-21