Data from: Molecular biogeography of prickly lettuce (Lactuca serriola L.) shows traces of recent range expansion

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 two 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 ten 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. AMOVA-based clustering indicated the presence of three populations 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 colonised 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 colonised areas than in the historical areas (Mantel’s r=0.20). In the newly colonised 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 colonisation from Eastern Europe, as well as a decrease of genetic diversity in recently established populations.

刺莴苣（*Lactuca serriola* L.，菊科Asteraceae）是栽培莴苣的野生近缘物种，属于自花授粉繁育类群，在过去两个世纪间于西欧和北欧实现了大规模扩张。本研究针对涵盖欧洲110个野生种群、共计2622个个体的数据集开展了大规模生物地理遗传分析，实验采用32个母系遗传的叶绿体限制性片段长度多态性（Restriction Fragment Length Polymorphism, RFLP）标记与10个核微卫星位点。微卫星分析结果显示，种群内部遗传变异水平较低且近交系数较高，同时种群间存在强烈的遗传分化，这与该物种的自花授粉繁育系统特征相符。基于分子变异方差分析（Analysis of Molecular Variance, AMOVA）的聚类分析表明，该物种可划分为3个种群簇，且三者均呈现显著的地理分布格局：第一簇分布于英国及北欧部分区域，其种群以单一优势基因型为典型特征；第二簇主要包含北欧地区的种群；第三簇则集中涵盖南欧种群。对刺莴苣基因多样性开展的克里金（Kriging）插值分析证实，其扩散路径为从中欧（东欧）向西北方向延伸。相较于历史分布区域，新近定殖区域的遗传多样性显著更低，这验证了奠基者效应的重要作用。在新近定殖区域中，地理距离较近的种群其遗传相似性高于历史分布区域，且距离隔离模式更为显著（Mantel检验r=0.20）。本研究结果证实了该物种近期从东欧快速向西北方向定殖的过程，以及新近建立种群的遗传多样性下降现象。