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）作物的形成受本地适应性、遗传漂变及种子交流介导的基因流共同驱动。反之，对地方品种种群间遗传结构的解析，可揭示上述演化力量随时间推移产生的影响。
本研究对40份瑞典田间豌豆（Pisum sativum L.）种群的遗传多样性展开分析，供试材料既包含19世纪晚期留存的历史种子样本，也涵盖20世纪晚期收集整合的现存基因库种质资源。
分析结果显示，历史种子样本始终维持着较高的种群内遗传多样性水平，而现存基因库种质资源的种群内遗传多样性则存在波动，且整体水平低于历史样本。
结构分析与主成分分析结果表明，绝大多数现存及历史种质资源均可按照地理起源聚类为不同类群。
郡域尺度的种质资源分析显示，历史种质资源的遗传多样性分布高度重叠；与之形成鲜明对比的是，多数现存种质资源均表现出遗传漂变的特征：它们仅携带历史种质资源中存在的部分等位基因，且种群间的遗传分化程度更高。
上述结果反映出：历史上广泛存在的集合种群虽在20世纪演变为遗传隔离的种群，但其核心遗传特征仍得以保留。