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Accumulation of Deleterious Mutations During Bacterial Range Expansions.

  • Bosshard L Computational and Molecular Population Genetics, Institute of Ecology an Evolution, University of Berne, 3012, Switzerland laurent.excoffier@iee.unibe.ch lars.bosshard@iee.unibe.ch.
  • Dupanloup I Computational and Molecular Population Genetics, Institute of Ecology an Evolution, University of Berne, 3012, Switzerland.
  • Tenaillon O French National Institute of Health and Medical Research, Infection Antimicrobials Modelling Evolution, UMR 1137, Paris, France; Université Paris Diderot, Sorbonne Paris Cité, France.
  • Bruggmann R Swiss Institute of Bioinformatics, 1015 Lausanne, Switzerland.
  • Ackermann M Institute of Biogeochemistry and Pollutant Dynamics, Swiss Federal Institute of Technology Zurich (ETH Zürich), 8092 Zürich, Switzerland.
  • Peischl S Swiss Institute of Bioinformatics, 1015 Lausanne, Switzerland.
  • Excoffier L Computational and Molecular Population Genetics, Institute of Ecology an Evolution, University of Berne, 3012, Switzerland laurent.excoffier@iee.unibe.ch lars.bosshard@iee.unibe.ch.
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  • 2017-08-20
Published in:
  • Genetics. - 2017
experimental evolution
mutation load
range expansions
Environment
Escherichia coli
Genetic Fitness
Genetic Load
Models, Genetic
Mutation
Mutation Rate
Selection, Genetic
English Recent theory predicts that the fitness of pioneer populations can decline when species expand their range, due to high rates of genetic drift on wave fronts making selection less efficient at purging deleterious variants. To test these predictions, we studied the fate of mutator bacteria expanding their range for 1650 generations on agar plates. In agreement with theory, we find that growth abilities of strains with a high mutation rate (HMR lines) decreased significantly over time, unlike strains with a lower mutation rate (LMR lines) that present three to four times fewer mutations. Estimation of the distribution of fitness effect under a spatially explicit model reveals a mean negative effect for new mutations (-0.38%), but it suggests that both advantageous and deleterious mutations have accumulated during the experiment. Furthermore, the fitness of HMR lines measured in different environments has decreased relative to the ancestor strain, whereas that of LMR lines remained unchanged. Contrastingly, strains with a HMR evolving in a well-mixed environment accumulated less mutations than agar-evolved strains and showed an increased fitness relative to the ancestor. Our results suggest that spatially expanding species are affected by deleterious mutations, leading to a drastic impairment of their evolutionary potential.
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  • English
Open access status
bronze
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https://sonar.ch/global/documents/45003
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