Tsuda Yoshiaki, Chen Jun, Stocks Michael, Källman Thomas, Sønstebø Jørn Henrik, Parducci Laura, Semerikov Vladimir, Sperisen Christoph, Politov Dmitry, Ronkainen Tiina, Väliranta Minna, Vendramin Giovanni Giuseppe, Tollefsrud Mari Mette, Lascoux Martin
Department of Ecology and Genetics, Evolutionary Biology Centre, Uppsala University, Norbyvägen 18D, 75236, Uppsala, Sweden.
CNR, Institute of Biosciences and Bioresources, Via Madonna del Piano 10, 50019, Sesto Fiorentino, Firenze, Italy.
Mol Ecol. 2016 Jun;25(12):2773-89. doi: 10.1111/mec.13654. Epub 2016 May 18.
Boreal species were repeatedly exposed to ice ages and went through cycles of contraction and expansion while sister species alternated periods of contact and isolation. The resulting genetic structure is consequently complex, and demographic inferences are intrinsically challenging. The range of Norway spruce (Picea abies) and Siberian spruce (Picea obovata) covers most of northern Eurasia; yet their geographical limits and histories remain poorly understood. To delineate the hybrid zone between the two species and reconstruct their joint demographic history, we analysed variation at nuclear SSR and mitochondrial DNA in 102 and 88 populations, respectively. The dynamics of the hybrid zone was analysed with approximate Bayesian computation (ABC) followed by posterior predictive structure plot reconstruction and the presence of barriers across the range tested with estimated effective migration surfaces. To estimate the divergence time between the two species, nuclear sequences from two well-separated populations of each species were analysed with ABC. Two main barriers divide the range of the two species: one corresponds to the hybrid zone between them, and the other separates the southern and northern domains of Norway spruce. The hybrid zone is centred on the Urals, but the genetic impact of Siberian spruce extends further west. The joint distribution of mitochondrial and nuclear variation indicates an introgression of mitochondrial DNA from Norway spruce into Siberian spruce. Overall, our data reveal a demographic history where the two species interacted frequently and where migrants originating from the Urals and the West Siberian Plain recolonized northern Russia and Scandinavia using scattered refugial populations of Norway spruce as stepping stones towards the west.
北方物种多次经历冰河时代，经历了收缩和扩张的循环，而其姊妹物种则经历了接触和隔离的交替时期。因此，由此产生的遗传结构很复杂，人口统计学推断本质上具有挑战性。挪威云杉（Picea abies）和西伯利亚云杉（Picea obovata）的分布范围覆盖了欧亚大陆北部的大部分地区；然而，它们的地理界限和历史仍知之甚少。为了划定这两个物种之间的杂交区并重建它们共同的人口统计学历史，我们分别分析了102个和88个种群的核简单序列重复（SSR）和线粒体DNA的变异。杂交区的动态通过近似贝叶斯计算（ABC）进行分析，随后进行后验预测结构图重建，并使用估计的有效迁移面测试整个分布范围内障碍的存在情况。为了估计这两个物种之间的分化时间，对每个物种两个相距较远的种群的核序列进行了ABC分析。两个主要障碍将这两个物种的分布范围分开：一个对应于它们之间的杂交区，另一个将挪威云杉的南部和北部分区分开。杂交区以乌拉尔山脉为中心，但西伯利亚云杉的遗传影响向西延伸得更远。线粒体和核变异的联合分布表明线粒体DNA从挪威云杉渗入西伯利亚云杉。总体而言，我们的数据揭示了一个人口统计学历史，即这两个物种频繁相互作用，来自乌拉尔山脉和西西伯利亚平原的迁徙者利用挪威云杉分散的避难种群作为向西的垫脚石，重新殖民了俄罗斯北部和斯堪的纳维亚半岛。
