The genetic structure of populations at the edge of species distribution is important for species adaptation to environmental changes. Small populations may experience non-random mating and differentiation due to genetic drift but larger populations, too, may have low effective size, e.g., due to the within-population structure. We studied spatial population structure of pedunculate oak, Quercus robur, at the northern edge of the species’ global distribution, where oak populations are experiencing rapid climatic and anthropogenic changes. Using 12 microsatellite markers, we analyzed genetic differentiation of seven small to medium size populations (census sizes 57–305 reproducing trees) and four populations for within-population genetic structures. Genetic differentiation among seven populations was low (Fst = 0.07). We found a strong spatial genetic structure in each of the four populations. Spatial autocorrelation was significant in all populations and its intensity (Sp) was higher than those reported in more southern oak populations. Significant genetic patchiness was revealed by Bayesian structuring and a high amount of spatially aggregated full and half sibs was detected by sibship reconstruction. Meta-analysis of isoenzyme and SSR data extracted from the (GD)² database suggested northwards decreasing trend in the expected heterozygosity and an effective number of alleles, thus supporting the central-marginal hypothesis in oak populations. We suggest that the fragmented distribution and location of Finnish pedunculate oak populations at the species’ northern margin facilitate the formation of within-population genetic structures. Information on the existence of spatial genetic structures can help conservation managers to design gene conservation activities and to avoid too strong family structures in the sampling of seeds and cuttings for afforestation and tree improvement purposes.

物种分布边缘的种群遗传结构对于物种适应环境变化至关重要。小种群可能由于遗传漂移而经历非随机的交配和分化，但大种群也可能具有较低的有效大小，例如由于种群内部结构。我们研究了有花梗栎栎的空间种群结构，位于该物种全球分布的北部边缘，那里的橡树种群正在经历快速的气候和人为变化。我们使用12个微卫星标记，分析了7个中小型种群（人口普查大小为57–305的繁殖树）和4个种群内部种群遗传结构的遗传分化。七个种群之间的遗传分化很低（Fst = 0.07）。我们在四个种群的每一个中都发现了强大的空间遗传结构。空间自相关在所有种群中均显着，其强度（Sp）高于在更多南部橡树种群中报告的强度。贝叶斯结构揭示了显着的遗传斑驳，并且通过同胞关系重建检测到大量空间聚集的同胞和半同胞。²数据库表明预期杂合度和有效等位基因数量向北下降趋势，从而支持了橡树种群的中央边缘假设。我们建议，该物种北缘的芬兰有花梗橡木种群的零散分布和位置有利于种群内部遗传结构的形成。有关空间遗传结构存在的信息可以帮助保护管理人员设计基因保护活动，并避免在用于造林和树木改良目的的种子和插条取样中使用过强的家庭结构。