State Key Laboratory of Earth Surface Processes and Resource Ecology and Ministry of Education Key Laboratory for Biodiversity Science and Ecological Engineering, College of Life Sciences, Beijing Normal University, Beijing 100875, China.
Key Laboratory of Tree Breeding and Cultivation of the National Forestry and Grassland, Research Institute of Forestry, Chinese Academy of Forestry, Beijing 100091, China.
Mol Phylogenet Evol. 2021 Jan;154:106964. doi: 10.1016/j.ympev.2020.106964. Epub 2020 Sep 19.
Hybridization has played an important role in plant evolution. Less attention has been paid, however, to its role in dispersal. In this study, historical divergence and hybridization were investigated in two closely related Chinese oaks, Quercus mongolica and Q. liaotungensis, to estimate the role that hybridization played in their dispersal. We genotyped 27 Q. mongolica and Q. liaotungensis populations throughout the distributional range of the two oak species, using 14 single-copy nuclear genes and four noncoding chloroplast DNA regions. Bayesian cluster and population tree analyses indicated that there were three groups over all oak populations, namely, Q. mongolica, northwest-northern China (NW-NC) Q. liaotungensis, and northeastern China (NEC) Q. liaotungensis. Approximate Bayesian computation simulation supported an asymmetrical hybridization origin of NEC Q. liaotungensis, after a previous divergence between NW-NC Q. liaotungensis and Q. mongolica. IMa3 analyses suggested that Q. liaotungensis and Q. mongolica diverged in the NW-NC and NEC regions, respectively, and that NEC Q. liaotungensis arose from Q. mongolica, not from NW-NC Q. liaotungensis, and was greatly introgressed by NW-NC Q. liaotungensis. Oak populations in NW-NC and NEC regions held different chloroplast DNA haplotypes, and Q. liaotungensis in NEC shared most haplotypes with Q. mongolica populations, but none with NW-NC Q. liaotungensis populations, suggesting the maternal origin of NEC Q. liaotungensis from Q. mongolica. This study found clear signals of isolation divergence of Q. liaotungensis in NW-NC and Q. mongolica in NEC, and the results suggest that asymmetrical hybridization and introgression from Q. liaotungensis to Q. mongolica, mostly likely via pollen flow, facilitated Q. liaotungensis dispersal to NEC.
杂交在植物进化中发挥了重要作用。然而，人们对其在扩散中的作用关注较少。在这项研究中，我们调查了两个密切相关的中国栎属树种蒙古栎和辽东栎的历史分化和杂交，以估计杂交在它们的扩散中所起的作用。我们对分布于蒙古栎和辽东栎两个种的 27 个种群进行了基因型分析，使用了 14 个单拷贝核基因和 4 个非编码叶绿体 DNA 区域。贝叶斯聚类和种群树分析表明，所有栎属种群总体上可分为三个组，即蒙古栎、西北-北方（NW-NC）辽东栎和东北（NEC）辽东栎。近似贝叶斯计算模拟支持，NEC 辽东栎是由 NW-NC 辽东栎与蒙古栎发生的不对称杂交而产生的。IMa3 分析表明，蒙古栎和辽东栎分别在 NW-NC 和 NEC 地区发生分化，NEC 辽东栎起源于蒙古栎，而不是 NW-NC 辽东栎，并且受到了 NW-NC 辽东栎的大量渗入。NW-NC 和 NEC 地区的栎属种群具有不同的叶绿体 DNA 单倍型，而 NEC 辽东栎与蒙古栎种群共享大多数单倍型，但与 NW-NC 辽东栎种群没有共享，这表明 NEC 辽东栎的母系起源于蒙古栎。本研究发现，NW-NC 辽东栎和 NEC 蒙古栎存在明显的隔离分化信号，结果表明，不对称杂交和辽东栎向蒙古栎的基因渗入，很可能是通过花粉流，促进了辽东栎向 NEC 的扩散。
