---
_id: '3644'
abstract:
- lang: eng
  text: "Wright proposed that there is a ' shifting balance' between selection within
    demes, random drift, and selection between demes at different 'adaptive peaks'.
    We investigate the establishment and spread of new adaptive peaks, considering
    a chromosome rearrangement, and a polygenic character under disruptive selection.
    When the number of migrants (Nm) is small, demes fluctuate independently, with
    a bias towards the fitter peak. When Nm is large, the whole population can\r\nmove
    to one of two stable equilibria, and so can be trapped near the lower peak. These
    two regimes are separated by a sharp transition at a critical Nm of order 1. Just
    below this critical point, adaptation is most efficient, since the shifting balance
    greatly increases the proportion of demes that reach the global optimum. This
    is so even if one peak is only slightly fitter than the other (AWx \\/N), and
    for both strong and weak selection (Ns <§ 1 or Ns > 1). Provided that Nm\r\nvaries
    sufficiently gradually from place to place, the fitter peak can be established
    in regions where Nm « 1, and can then spread through the rest of the range. Our
    analysis confirms Wright's argument that if selection, migration and drift are
    of the same order, the ' shifting balance' leads to efficient evolution towards
    the global optimum."
article_processing_charge: No
article_type: original
author:
- first_name: Nicholas H
  full_name: Barton, Nicholas H
  id: 4880FE40-F248-11E8-B48F-1D18A9856A87
  last_name: Barton
  orcid: 0000-0002-8548-5240
- first_name: Shahin
  full_name: Rouhani, Shahin
  last_name: Rouhani
citation:
  ama: Barton NH, Rouhani S. Adaptation and the “shifting balance.” <i>Genetical Research</i>.
    1993;61(1):57-74. doi:<a href="https://doi.org/10.1017/S0016672300031098 ">10.1017/S0016672300031098
    </a>
  apa: Barton, N. H., &#38; Rouhani, S. (1993). Adaptation and the “shifting balance.”
    <i>Genetical Research</i>. Cambridge University Press. <a href="https://doi.org/10.1017/S0016672300031098
    ">https://doi.org/10.1017/S0016672300031098 </a>
  chicago: Barton, Nicholas H, and Shahin Rouhani. “Adaptation and the ‘Shifting Balance.’”
    <i>Genetical Research</i>. Cambridge University Press, 1993. <a href="https://doi.org/10.1017/S0016672300031098
    ">https://doi.org/10.1017/S0016672300031098 </a>.
  ieee: N. H. Barton and S. Rouhani, “Adaptation and the ‘shifting balance,’” <i>Genetical
    Research</i>, vol. 61, no. 1. Cambridge University Press, pp. 57–74, 1993.
  ista: Barton NH, Rouhani S. 1993. Adaptation and the ‘shifting balance’. Genetical
    Research. 61(1), 57–74.
  mla: Barton, Nicholas H., and Shahin Rouhani. “Adaptation and the ‘Shifting Balance.’”
    <i>Genetical Research</i>, vol. 61, no. 1, Cambridge University Press, 1993, pp.
    57–74, doi:<a href="https://doi.org/10.1017/S0016672300031098 ">10.1017/S0016672300031098
    </a>.
  short: N.H. Barton, S. Rouhani, Genetical Research 61 (1993) 57–74.
date_created: 2018-12-11T12:04:24Z
date_published: 1993-02-01T00:00:00Z
date_updated: 2022-03-30T08:18:58Z
day: '01'
doi: '10.1017/S0016672300031098 '
extern: '1'
intvolume: '        61'
issue: '1'
language:
- iso: eng
main_file_link:
- url: https://www.cambridge.org/core/journals/genetics-research/article/adaptation-and-the-shifting-balance/2E15452B3AFCA97E77743E0C7E108064
month: '02'
oa_version: None
page: 57 - 74
publication: Genetical Research
publication_identifier:
  issn:
  - 0016-6723
publication_status: published
publisher: Cambridge University Press
publist_id: '2739'
quality_controlled: '1'
scopus_import: '1'
status: public
title: Adaptation and the 'shifting balance'
type: journal_article
user_id: ea97e931-d5af-11eb-85d4-e6957dddbf17
volume: 61
year: '1993'
...