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，属于自花授粉物种，在过去两个世纪间于西欧与北欧大幅扩张。本研究针对来自欧洲110个野生种群的2622个个体构建的数据集，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标记（chloroplast RFLP-markers）与10个核微卫星位点（nuclear microsatellite loci）进行分型。微卫星分析结果显示，种群内部遗传变异水平较低、近交系数较高，同时种群间存在显著遗传分化，这与该物种的自花授粉繁育系统相符。基于分子方差分析（AMOVA）的聚类结果表明存在三个种群集群，且呈现出强烈的地理分布格局：第一集群分布于英国及北欧部分区域，其种群均以单一优势基因型为特征；第二集群主要涵盖北欧种群；第三集群则以欧洲南部种群为主。对刺莴苣的基因多样性开展克里金插值（Kriging）分析后证实，该物种从欧洲中部（东部）地区向北、向西扩散。新定植区域的遗传多样性显著低于历史分布区域，印证了奠基者效应（founder effects）的重要作用。相较于历史分布区域，新定植区域的距离隔离（isolation by distance）模式更为显著（曼特尔r值Mantel’s r=0.20）：在新定植区域内，地理距离较近的种群遗传相似性高于历史分布区域。本研究结果证实，该物种近期从东欧快速向北、向西扩张，且新近建立的种群遗传多样性呈下降趋势。