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

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, 9 for Laminaria hyperborea and 11 for Laminaria digitata, of which 8 amplified in both species. The genetic diversity and connectivity of L. hyperborea populations was greater than that 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. dig...