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Geographical delimitation of a partial selective sweep in African Drosophila melanogaster

Authors

  • L. Frezal,

    Corresponding author
    • Laboratoire Biologie intégrative des populations, Ecole Pratique des Hautes Etudes, Paris, France
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    • co-first authors.
  • F. Meli,

    1. Laboratoire Biologie intégrative des populations, Ecole Pratique des Hautes Etudes, Paris, France
    2. CNRS UMR 7205, Muséum National d'Histoire Naturelle, Paris, France
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    • co-first authors.
  • S. Mousset,

    1. Laboratoire Biologie intégrative des populations, Ecole Pratique des Hautes Etudes, Paris, France
    Current affiliation:
    1. Biométrie et Biologie Évolutive, CNRS UMR 5558, Université Claude Bernard, Villeurbanne, France
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  • S. Mona,

    1. Laboratoire Biologie intégrative des populations, Ecole Pratique des Hautes Etudes, Paris, France
    2. CNRS UMR 7205, Muséum National d'Histoire Naturelle, Paris, France
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  • M. Veuille

    Corresponding author
    1. CNRS UMR 7205, Muséum National d'Histoire Naturelle, Paris, France
    • Laboratoire Biologie intégrative des populations, Ecole Pratique des Hautes Etudes, Paris, France
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Correspondence: Michel Veuille, Institut de Biologie de l’Ecole Normale Supérieure, CNRS - ENS - Inserm, 46 rue d'Ulm, 75230 Paris cedex 05, France. Fax: +33-0- 140793342; E-mail: veuille@mnhn.fr

Abstract

Positive selection leaves characteristic footprints on DNA variation but detecting such patterns is challenging as the age, the intensity and the mode of selection as well as demography and evolutionary parameters (mutation and recombination rates) all play roles and these are difficult to disentangle. We recorded nucleotide variation in a sample of isogenic chromosomes from a western African population of Drosophila melanogaster at a locus (Fbp2) for which a partial selective sweep had previously been reported. We compared this locus to four other genes from the same chromosomes and from a European and an East African population. Then, we assessed Fbp2 variation in a sample of 370 chromosomes covering a comprehensive geographic sampling of 16 African localities. The signature of selection was tested while accounting for the demographic history of the populations. We found a significant signal of selection in two West African localities including Ivory Coast. Variation at Fpb2 would thus represent a case of an ongoing selective sweep in the range of this species. A weaker, nonsignificant, signal of selection was, however, apparent in some other populations, thus leaving open several possibilities: (i) the selective sweep originated in Ivory Coast and has spread to the rest of the continent; (ii) several African populations report the signature of a selective event having occurred in an ancestral population; (iii) this genome region is subject to independent selective events in African populations; and (iv) A neutral scenario with population subdivision and local bottleneck cannot be fully excluded to explain the molecular patterns observed in some populations.

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