Data from: 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. digitata encounters its southern range limit in southern Brittany 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 southern Brittany, 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.

本研究以两种姐妹海带物种为研究对象，旨在探究沿潮间带的分布宽度、带状分布格局、纬度分布范围以及历史因素如何造就二者迥异的遗传多样性模式。我们采用分层采样方案，针对法国布列塔尼海岸同域分布的这两种海带物种，利用共计12个微卫星（microsatellites）标记开展遗传多样性与遗传结构的比较分析：其中9个标记适用于掌状海带（Laminaria hyperborea），11个适用于糖海带（Laminaria digitata），另有8个标记可在两个物种中均实现扩增。研究结果表明，掌状海带种群的遗传多样性与连通性均显著高于糖海带种群，这与其沿海岸的跨岸分布范围更广、占据水深更深的特征一致。此外，边缘种群的遗传多样性与连通性均出现下降，这消除了两个物种的距离隔离（isolation-by-distance）格局。鉴于糖海带在布列塔尼南部处于其分布范围的南界，而掌状海带的分布范围可延伸至葡萄牙中部，因此我们得以区分生境连续性与分布边缘效应的影响。我们发现，糖海带在其分布南缘并未呈现典型的后缘种群所应有的高区域遗传多样性，这暗示末次冰盛期时糖海带的避难所可能并不位于布列塔尼南部，而更可能位于更北的区域。对于两个物种而言，遗传多样性水平最高的区域均为伊罗伊斯海（Iroise Sea）和莫尔莱湾（Morlaix Bay），这两个区域也是目前二者的主要捕捞产区。因此，在上述区域保护这两种关键奠基物种的遗传多样性，应当成为布列塔尼该渔业资源管理的优先事项。