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The maintenance of standing genetic variation: gene flow versus selective neutrality in Atlantic stickleback fish
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  • Quiterie Haenel,
  • Laurent Guerard,
  • Andrew MacColl,
  • Daniel Berner
Quiterie Haenel
University of Basel
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Laurent Guerard
Basel University Biozentrum Department
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Andrew MacColl
University of Nottingham
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Daniel Berner
University of Basel
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Abstract

Adaptation to derived habitats often occurs from standing genetic variation (SGV). The maintenance within ancestral populations of genetic variants favorable in derived habitats is commonly ascribed to long-term antagonism between purifying selection and gene flow resulting from hybridization across habitats. A largely unexplored alternative idea based on quantitative genetic models of polygenic adaptation is that variants favored in derived habitats are neutral in ancestral populations when their frequency is relatively low. To explore the latter, we first identify genetic variants important to the adaptation of threespine stickleback fish to a rare derived habitat – nutrient-depleted acidic lakes – based on whole-genome sequence data. Sequencing marine stickleback from six locations across the Atlantic ocean then allows us to infer that the frequency of these derived variants in the ancestral habitat is unrelated to the likely opportunity for gene flow of these variants from acidic-adapted populations. This result is consistent with the selective neutrality of derived variants within the ancestor. Our study thus supports an underappreciated explanation for the maintenance of SGV, and calls for a better understanding of the fitness consequences of adaptive genetic variation across habitats and genomic backgrounds.

Peer review status:IN REVISION

15 Jul 2021Submitted to Molecular Ecology
16 Jul 2021Assigned to Editor
16 Jul 2021Submission Checks Completed
27 Jul 2021Reviewer(s) Assigned
09 Sep 2021Review(s) Completed, Editorial Evaluation Pending
17 Sep 2021Editorial Decision: Revise Minor