1. Evolutionary Biology
  2. Physics of Living Systems
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Environmental heterogeneity can tip the population genetics of range expansions

  1. Matti Gralka
  2. Oskar Hallatschek  Is a corresponding author
  1. University of California, Berkeley, United States
Research Article
  • Cited 7
  • Views 1,554
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Cite this article as: eLife 2019;8:e44359 doi: 10.7554/eLife.44359


The population genetics of most range expansions is thought to be shaped by the competition between Darwinian selection and random genetic drift at the range margins. Here, we show that the evolutionary dynamics during range expansions is highly sensitive to additional fluctuations induced by environmental heterogeneities. Tracking mutant clones with a tunable fitness effect in bacterial colonies grown on randomly patterned surfaces we found that environmental heterogeneity can dramatically reduce the efficacy of selection. Time-lapse microscopy and computer simulations suggest that this effect arises generically from a local 'pinning' of the expansion front, whereby stretches of the front are slowed down on a length scale that depends on the structure of the environmental heterogeneity. This pinning focuses the range expansion into a small number of 'lucky' individuals with access to expansion paths, altering the neutral evolutionary dynamics and increasing the importance of chance relative to selection.

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Author details

  1. Matti Gralka

    Department of Physics, University of California, Berkeley, Berkeley, United States
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0003-4599-1859
  2. Oskar Hallatschek

    Department of Physics, University of California, Berkeley, Berkeley, United States
    For correspondence
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0002-1312-5975


Simons Foundation

  • Oskar Hallatschek

National Science Foundation

  • Oskar Hallatschek

National Institute of General Medical Sciences

  • Oskar Hallatschek

The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.

Reviewing Editor

  1. Richard A Neher, University of Basel, Switzerland

Publication history

  1. Received: December 18, 2018
  2. Accepted: April 11, 2019
  3. Accepted Manuscript published: April 12, 2019 (version 1)
  4. Version of Record published: May 13, 2019 (version 2)


© 2019, Gralka & Hallatschek

This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.


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