Data from: Local coastal configuration rather than latitudinal gradient shape clonal diversity and genetic structure of Phymatolithon calcareum maerl beds in North European Atlantic

Maerl beds are one of the world’s key coastal ecosystems and are threatened by human activities and global change. In this study, the genetic diversity and structure of one of the major European maerl-forming species, Phymatolithon calcareum, was studied using eight microsatellite markers. Two sampling scales (global: North East Atlantic and regional: Galicia) were investigated and fifteen maerl beds from Atlantic Europe were sampled. At the regional-scale the location of sites outside and within four estuaries allowed to test for the influence of coastal configuration on population connectivity and genetic diversity. Results suggested that clonal reproduction plays an important role in the population dynamics of P. calcareum maerl beds. Clonality was variable among populations, even within the same region. At the European scale, these differences in clonality cannot be explained by the geographic or latitudinal distribution of the populations studied. A significant genetic differentiation was found among almost all population pairs and a positive correlation between geographic and genetic distances showed the limited dispersal capacity of P. calcareum. Moreover, a very clear pattern of genetic structure was revealed at the regional scale between populations located within and at the mouth of the estuaries. Genetic differentiation among estuaries was less marked for the sites located in outer-zones compared to those located in the inner-zones. In addition, variation in level of clonality linked to seascape was also observed: populations situated in the outer-zones of the estuaries were less clonal than those in the inner-zones. Finally, populations from the same estuary generally shared one or several mutilocus genotypes.

钙化藻床（maerl beds）是全球关键海岸生态系统之一，正面临人类活动与全球变化带来的威胁。本研究以欧洲主要的钙化藻形成物种之一——钙化拟石藻（Phymatolithon calcareum）为研究材料，采用8个微卫星标记（microsatellite markers）对其遗传多样性与种群结构进行了分析。研究设置两级采样尺度：全球尺度（东北大西洋）与区域尺度（西班牙加利西亚区域），共在大西洋欧洲沿岸采集了15处钙化藻床样本。在区域尺度下，研究选取了4个河口的内外区域采样点，以此检验海岸格局对种群连通性与遗传多样性的影响。研究结果显示，无性繁殖（clonal reproduction）在钙化拟石藻的种群动态中扮演重要角色。不同种群间的无性繁殖水平存在显著差异，即便在同一区域内亦不例外。在欧洲全域尺度下，种群间的无性繁殖差异无法通过研究种群的地理分布或纬度分布加以解释。几乎所有种群对之间均存在显著的遗传分化（genetic differentiation），且地理距离与遗传距离呈正相关，这表明钙化拟石藻的扩散能力有限。此外，在区域尺度上，河口内部与河口入口处的种群间呈现出极为清晰的遗传结构模式。相较于河口内区采样点，河口外区采样点的种群间遗传分化程度相对较弱。同时，研究还观察到无性繁殖水平与海洋景观格局存在关联：河口外区种群的无性繁殖水平低于河口内区种群。最后，同一河口内的种群通常共享一个或多个多位点基因型（multilocus genotypes）。