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种，为自花授粉物种，近两个世纪以来在西欧与北欧大范围扩张。本研究基于涵盖欧洲110个野生种群的2622个个体构建数据集，开展了大规模生物地理遗传学分析。研究采用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、近交系数偏高，且种群间存在显著遗传分化，这与该物种的自交繁育系统特征相符。基于分子变异分析（Analysis of Molecular Variance，AMOVA）的聚类分析表明，该物种可划分为3个种群集群，且呈现出清晰的地理分布格局：其中一个集群分布于英国及北欧部分区域，其种群内仅存在单一优势基因型；第二个集群主要包含北欧种群；第三个集群则以欧洲南部种群为主。对刺莴苣（*Lactuca serriola*）的基因多样性开展克里金插值（Kriging）分析，结果证实该物种的扩散路径为从中欧（东欧）向北欧与西欧扩张。相较于历史分布区，新定植区域的遗传多样性水平显著更低，这证实了奠基者效应（Founder Effect）的重要作用。新定植区域的距离隔离模式相较于历史分布区更为显著（曼特尔检验r=0.20）。在新定植区域中，地理距离较近的种群遗传相似性高于历史分布区内的种群。本研究结果证实，该物种近期从东欧快速向北欧与西欧扩张，且新近建立的种群遗传多样性有所降低。