Fievet Virgil, Touzet Pascal, Arnaud Jean-François, Cuguen Joël
UMR CNRS 8016, FR 1818, Laboratoire de Génétique et Evolution des Populations Végétales, Université de Lille 1, Bâtiment SN2, 59655 Villeneuve d'Ascq cedex, France.
Mol Ecol. 2007 May;16(9):1847-64. doi: 10.1111/j.1365-294X.2006.03208.x.
Patterns of seed dispersal in the wild sea beet (Beta vulgaris ssp. maritima) are predicted to be influenced by marine currents because populations are widely distributed along the European Atlantic coast. We investigated the potential influence of marine currents on the pattern of spatial genetic structuring in natural populations of sea beet. Populations were located along the French coasts of the Anglo-Norman gulf that features peculiar marine currents in the Channel. Thirty-three populations were sampled, among which 23 were continental and 10 were insular populations located in Jersey, Guernsey and Chausey, for a total of 1224 plants genotyped. To validate the coastal topography influence and the possibility of marine current orientated gene flow on the genetic features of sea beet populations, we assessed patterns of genetic structuring of cytoplasmic and nuclear diversity by: (i) searching for an isolation-by-distance (IBD) pattern using spatial autocorrelation tools; (ii) using the Monmonier algorithm to identify genetic boundaries in the area studied; and (iii) performing assignment tests that are based on multilocus genotype information to ascertain population membership of individuals. Our results showed a highly contrasted cytoplasmic and nuclear genetic differentiation and highlighted the peculiar situation of island populations. Beyond a classical isolation-by-distance due to short-range dispersal, genetic barriers fitting the orientation of marine currents were clearly identified. This suggests the occurrence of long-distance seed dispersal events and an asymmetrical gene flow separating the eastern and western part of the Anglo-Norman gulf.
野生海甜菜（Beta vulgaris ssp. maritima）的种子传播模式预计会受到海流的影响，因为其种群广泛分布于欧洲大西洋沿岸。我们调查了海流对海甜菜自然种群空间遗传结构模式的潜在影响。种群分布在英吉利海峡具有独特海流的法国诺曼底海湾沿岸。共采集了33个种群的样本，其中23个是大陆种群，10个是位于泽西岛、根西岛和肖西岛的岛屿种群，总计对1224株植物进行了基因分型。为了验证海岸地形的影响以及海流导向的基因流对海甜菜种群遗传特征的可能性，我们通过以下方式评估细胞质和核多样性的遗传结构模式：（i）使用空间自相关工具寻找距离隔离（IBD）模式；（ii）使用蒙莫尼尔算法识别研究区域内的遗传边界；（iii）基于多位点基因型信息进行赋值测试，以确定个体的种群归属。我们的结果显示出细胞质和核遗传分化的高度对比，并突出了岛屿种群的特殊情况。除了由于短距离传播导致的经典距离隔离外，还明确识别出了与海流方向相符的遗传屏障。这表明发生了长距离种子传播事件以及将诺曼底海湾东部和西部分开的不对称基因流。
