Caspian poplar (Populus caspica Bornm.) is an endemic species from Hyrcanian forests and classified as endangered in Iran. However, there is little information about population genetic structure of remnant populations that could support the development of the suitable conservation strategy for this species. This study was designed to understand how anthropogenic and environmental factors have influenced the pattern of genetic diversity of P. caspica. We sampled 359 individuals from 20 populations. However, after removing the clonal ramets, the genetic parameters were calculated for 314 trees using 14 microsatellite markers. Nine populations showed a significant reduction in effective population size and a genetic bottleneck. The inbreeding coefficient (F_IS) ranged from 0.02 to 0.11, and the pairwise F_ST from 0.018 to 0.224, indicating a low to high level of differentiation among populations. The average proportion of migrants was low (0.008), and it was revealed that the Alborz mountains are a major barrier to gene flow between P. caspica populations in the Hyrcanian forests. Resistance analysis showed that elevation is a significant barrier for gene flow across the eastern and western range of the species. STRUCTURE analysis showed the existence of at least two genetic clusters, whereas GENELAND estimated the number of clusters as three. We propose the maintenance of three natural management units to reduce the risk of extinction of this species in the near future.

里海杨树（Populus caspica Bornm。）是来自Hyrcanian森林的特有物种，在伊朗被列为濒危物种。但是，关于剩余种群的种群遗传结构的信息很少，可以支持该物种的适当保护策略的发展。本研究的目的是了解人为和环境因素如何影响了C. caspica的遗传多样性模式。我们从20个人口中抽样了359个人。但是，在删除克隆分株后，使用14个微卫星标记为314棵树计算了遗传参数。九个种群显示有效种群数量显着减少和遗传瓶颈。近交系数（F _IS）的范围从0.02到0.11，成对的F _ST从0.018到0.224，表明人群之间的分化程度从低到高。移民的平均比例很低（0.008），并且揭示了阿尔伯兹山脉是Hyrcanian森林中C. caspica种群之间基因交流的主要障碍。抗性分析表明，海拔升高是跨越该物种东部和西部范围的基因流动的重要障碍。结构分析表明存在至少两个遗传簇，而GENELAND估计该簇为三个。我们建议维护三个自然管理单位，以减少在不久的将来该物种灭绝的风险。