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Microsatellite length variation in candidate genes correlates with habitat in the gilthead sea bream Sparus aurata

Authors

  • Lamya Chaoui,

    1. Institut des Sciences de l'Evolution (ISEM-CNRS, UMR 5554), Université Montpellier II, SMEL, Sète, France
    2. Laboratoire Bioressources Marines – Badji Mokhtar, Université d'Annaba, Oued Kouba, Annaba, Algeria
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    • Both authors have equally contributed.

  • Pierre-Alexandre Gagnaire,

    1. Institut des Sciences de l'Evolution (ISEM-CNRS, UMR 5554), Université Montpellier II, SMEL, Sète, France
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    • Both authors have equally contributed.

  • Bruno Guinand,

    1. Institut des Sciences de l'Evolution (ISEM-CNRS, UMR 5554), Université Montpellier II, SMEL, Sète, France
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  • Jean-Pierre Quignard,

    1. Laboratoire d'Ichtyologie Méditerranéenne, Castelnau-Le-Lez, France
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  • Costas Tsigenopoulos,

    1. Institute of Marine Biology, Biotechnology and Aquaculture, Hellenic Centre for Marine Research (HCMR) Crete, Heraklion, Greece
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  • M. Hichem Kara,

    1. Laboratoire Bioressources Marines – Badji Mokhtar, Université d'Annaba, Oued Kouba, Annaba, Algeria
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  • François Bonhomme

    Corresponding author
    • Institut des Sciences de l'Evolution (ISEM-CNRS, UMR 5554), Université Montpellier II, SMEL, Sète, France
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Correspondence: François Bonhomme, Fax: 33 4 67 14 4554;
E-mail: francois.bonhomme@univ-montp2.fr

Abstract

The genetic basis and evolutionary implications of local adaptation in high gene flow marine organisms are still poorly understood. In several Mediterranean fish species, alternative migration patterns exist between individuals entering coastal lagoons that offer favourable conditions for growth and those staying in the sea where environmental conditions are less subject to rapid and stressful change. Whether these coexisting strategies are phenotypically plastic or include a role for local adaptation through differential survival needs to be determined. Here, we explore the genetic basis of alternate habitat use in western Mediterranean populations of the gilthead sea bream (Sparus aurata). Samples from lagoonal and open-sea habitats were typed for three candidate gene microsatellite loci, seven anonymous microsatellites and 44 amplified fragment length polymorphism markers to test for genotype–environment associations. While anonymous markers globally indicated high levels of gene flow across geographic locations and habitats, non-neutral differentiation patterns correlated with habitat type were found at two candidate microsatellite loci located in the promoter region of the growth hormone and prolactin genes. Further analysis of these two genes revealed that a mechanism based on habitat choice alone could not explain the distribution of genotype frequencies at a regional scale, thus implying a role for differential survival between habitats. We also found an association between allele size and habitat type, which, in the light of previous studies, suggests that polymorphisms in the proximal promoter region could influence gene expression by modulating transcription factor binding, thus providing a potential explanatory link between genotype and growth phenotype in nature.

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