Contrasting genetic diversity patterns in two sister kelp species co-distributed along the coast of Brittany, France

Authors

  • Marine Robuchon,

    Corresponding author
    1. ISYEB Institut, UMR 7205 CNRS-EPHE-MNHN-UPMC, Equipe Exploration, Espèces et Evolution, Muséum National d'Histoire Naturelle, Cedex 05 Paris, France
    2. CNRS, UMR 7144 Adaptation et Diversité en Milieu Marin, Equipe BEDIM, Roscoff, France
    3. Sorbonne Universités, UPMC Univ Paris 06, UMR 7144 Adaptation et Diversité en Milieu Marin, Equipe BEDIM, Roscoff, France
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  • Line Le Gall,

    1. ISYEB Institut, UMR 7205 CNRS-EPHE-MNHN-UPMC, Equipe Exploration, Espèces et Evolution, Muséum National d'Histoire Naturelle, Cedex 05 Paris, France
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  • Stéphane Mauger,

    1. CNRS, UMR 7144 Adaptation et Diversité en Milieu Marin, Equipe BEDIM, Roscoff, France
    2. Sorbonne Universités, UPMC Univ Paris 06, UMR 7144 Adaptation et Diversité en Milieu Marin, Equipe BEDIM, Roscoff, France
    Current affiliation:
    1. UMI 3614 Evolutionary Biology and Ecology of Algae, CNRS, UPMC, Roscoff, France
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  • Myriam Valero

    Corresponding author
    1. CNRS, UMR 7144 Adaptation et Diversité en Milieu Marin, Equipe BEDIM, Roscoff, France
    2. Sorbonne Universités, UPMC Univ Paris 06, UMR 7144 Adaptation et Diversité en Milieu Marin, Equipe BEDIM, Roscoff, France
    Current affiliation:
    1. UMI 3614 Evolutionary Biology and Ecology of Algae, CNRS, UPMC, Roscoff, France
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Abstract

We investigated patterns of genetic structure in two sister kelp species to explore how distribution width along the shore, zonation, latitudinal distribution and historical factors contribute to contrasting patterns of genetic diversity. We implemented a hierarchical sampling scheme to compare patterns of genetic diversity and structure in these two kelp species co-distributed along the coasts of Brittany (France) using a total of 12 microsatellites, nine for Laminaria hyperborea and 11 for Laminaria digitata, of which eight amplified in both species. The genetic diversity and connectivity of L. hyperborea populations were greater than those of L. digitata populations in accordance with the larger cross-shore distribution width along the coast and the greater depth occupied by L. hyperborea populations in contrast to L. digitata populations. In addition, marginal populations showed reduced genetic diversity and connectivity, which erased isolation-by-distance patterns in both species. As L. digitata encounters its southern range limit in southern Brittany (SBr) while L. hyperborea extends down to mid-Portugal, it was possible to distinguish the effect of habitat continuity from range edge effects. We found that L. digitata did not harbour high regional diversity at its southern edge, as expected in a typical rear edge, suggesting that refuges from the last glacial maximum for L. digitata were probably not located in SBr, but most likely further north. For both species, the highest levels of genetic diversity were found in the Iroise Sea and Morlaix Bay, the two regions in which they are being currently harvested. Preserving genetic diversity of these two foundation species in these areas should, thus, be a priority for the management of this resource in Brittany.

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