Accumulation of Deleterious Mutations During Bacterial Range Expansions

Bosshard, Lars; Dupanloup, Isabelle; Tenaillon, Olivier; Bruggmann, Rémy; Ackermann, Martin; Peischl, Stephan; Excoffier, Laurent (2017). Accumulation of Deleterious Mutations During Bacterial Range Expansions. Genetics, 207(2), pp. 669-684. Genetics Society of America 10.1534/genetics.117.300144

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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 (20.38%), 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 wellmixed 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.

Item Type:

Journal Article (Original Article)


08 Faculty of Science > Department of Biology > Institute of Ecology and Evolution (IEE)
08 Faculty of Science > Department of Biology > Institute of Ecology and Evolution (IEE) > Population Genetics
08 Faculty of Science > Department of Biology > Bioinformatics and Computational Biology

UniBE Contributor:

Bosshard, Lars, Duperret, Isabelle, Bruggmann, Rémy, Peischl, Stephan, Excoffier, Laurent


500 Science > 570 Life sciences; biology




Genetics Society of America




Susanne Holenstein

Date Deposited:

23 Jul 2018 14:23

Last Modified:

23 Dec 2022 09:51

Publisher DOI:





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