Data from: Twentieth-century changes in the genetic composition of Swedish field pea metapopulations

Landrace crops are formed by local adaptation, genetic drift and gene flow through seed exchange. In reverse, the study of genetic structure between landrace populations can reveal the effects of these forces over time. We present here the analysis of genetic diversity in 40 Swedish field pea (Pisum sativum L.) populations, either available as historical seed samples from the late nineteenth century or as extant gene bank accessions assembled in the late twentieth century. The historical material shows constant high levels of within-population diversity, whereas the extant accessions show varying, and overall lower, levels of within-population diversity. Structure and principal component analysis cluster most accessions, both extant and historical, in groups after geographical origin. County-wise analyses of the accessions show that the genetic diversity of the historical accessions is largely overlapping. In contrast, most extant accessions show signs of genetic drift. They harbor a subset of the alleles found in the historical accessions and are more differentiated from each other. These results reflect how, historically present metapopulations have been preserved during the twentieth century, although as genetically isolated populations.地方品种（Landrace）作物的形成，是本地适应、遗传漂变与种子交换介导的基因流共同作用的结果。反之，对地方品种种群间遗传结构的研究，能够揭示这些演化动力随时间推移产生的影响。本研究针对40个瑞典豌豆（Pisum sativum L.）种群的遗传多样性开展分析，所用材料既包含19世纪晚期留存的历史种子样本，也包括20世纪晚期收集并入库保存的基因库现存种质份样。历史样本的种群内遗传多样性始终维持在较高水平，而现存种质份样的种群内遗传多样性则呈现波动特征，且整体水平低于历史样本。群体结构分析与主成分分析结果显示，绝大多数现存与历史种质份样均可依据地理来源聚类分组。按郡级行政单位开展的种质份样分析表明，历史种质份样的遗传多样性分布高度重叠。与之相对，绝大多数现存种质份样均表现出遗传漂变的特征：它们仅保留了历史种质份样中的部分等位基因，且种群间的遗传分化程度更高。上述结果反映出：20世纪期间，历史上原本存在的集合种群（metapopulation）虽已演变为遗传上相互隔离的种群，但仍得以保存至今。