D'Andrea Luigi, Meirmans Patrick, van de Wiel Clemens, Guadagnuolo Roberto, van Treuren Robbert, Kozlowski Gregor, den Nijs Hans, Felber François
Laboratoire de Botanique évolutive, Institut de Biologie, Université de Neuchâtel, Rue Emile-Argand 11, Neuchâtel, Switzerland.
Institute for Biodiversity & Ecosystem Dynamics (UvA), University of Amsterdam, Amsterdam, The Netherlands.
J Hered. 2017 Mar 1;108(2):194-206. doi: 10.1093/jhered/esw078.
Prickly lettuce (Lactuca serriola L., Asteraceae), a wild relative of cultivated lettuce, is an autogamous species which greatly expanded throughout Western and Northern Europe during the last 2 centuries. Here, we present a large-scale biogeographic genetic analysis performed on a dataset represented by 2622 individuals from 110 wild European populations. Thirty-two maternally inherited chloroplast RFLP-markers and 10 nuclear microsatellite loci were used. Microsatellites revealed low genetic variation and high inbreeding coefficients within populations, as well as strong genetic differentiation between populations, which was in accordance with the autogamous breeding system. Analysis of molecular variance based clustering indicated the presence of 3 population clusters, which showed strong geographical patterns. One cluster occupied United Kingdom and part of Northern Europe, and characterized populations with a single predominant genotype. The second mostly combined populations from Northern Europe, while the third cluster grouped populations particularly from Southern Europe. Kriging of gene diversity for L. serriola corroborated northwards and westwards spread from Central (Eastern) Europe. Significant lower genetic diversity characterized the newly colonized parts of the range compared to the historical ones, confirming the importance of founder effects. Stronger pattern of isolation by distance was assessed in the newly colonized areas than in the historical areas (Mantel’s r = 0.20). In the newly colonized areas, populations at short geographic distances were genetically more similar than those in the historical areas. Our results corroborate the species’ recent and rapid northward and westward colonization from Eastern Europe, as well as a decrease of genetic diversity in recently established populations.
刺叶莴苣（Lactuca serriola L.，菊科）是栽培生菜的野生近缘种，是一种自花授粉物种，在过去两个世纪中在西欧和北欧广泛分布。在此，我们对来自110个欧洲野生种群的2622个个体组成的数据集进行了大规模生物地理遗传分析。使用了32个母系遗传的叶绿体RFLP标记和10个核微卫星位点。微卫星显示种群内遗传变异低、近亲繁殖系数高，以及种群间强烈的遗传分化，这与自花授粉的繁殖系统一致。基于分子方差分析的聚类表明存在3个种群簇，呈现出强烈的地理格局。一个簇占据英国和北欧部分地区，其种群具有单一的主要基因型。第二个簇主要合并了来自北欧的种群，而第三个簇则将特别是来自南欧的种群归为一组。刺叶莴苣基因多样性的克里金插值法证实了其从欧洲中部（东部）向北和向西的扩散。与历史区域相比，该分布范围新殖民部分的遗传多样性显著较低，证实了奠基者效应的重要性。新殖民地区的距离隔离模式比历史地区更强（Mantel's r = 0.20）。在新殖民地区，地理距离短的种群在遗传上比历史地区的种群更相似。我们的结果证实了该物种最近从东欧迅速向北和向西的殖民化，以及新建立种群中遗传多样性的降低。
