Ancient introgression can be an important source of genetic variation that shapes the evolution and diversification of many taxa. Here, we estimate the timing, direction, and extent of gene flow between two distantly related oak species in the same section (Quercus sect. Quercus). We estimated these demographic events using genotyping by sequencing data, which generated 25 702 single nucleotide polymorphisms for 24 individuals of California scrub oak (Quercus berberidifolia) and 23 individuals of Engelmann oak (Quercus engelmannii). We tested several scenarios involving gene flow between these species using the diffusion approximation-based population genetic inference framework and model-testing approach of the Python package DaDi. We found that the most likely demographic scenario includes a bottleneck in Q. engelmannii that coincides with asymmetric gene flow from Q. berberidifolia into Q. engelmannii. Given that the timing of this gene flow coincides with the advent of a Mediterranean-type climate in the California Floristic Province, we propose that changing precipitation patterns and seasonality may have favored the introgression of climate-associated genes from the endemic into the non-endemic California oak.

中文翻译：

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远缘白橡树（Quercus sect. Quercus）之间的古代基因渗入显示了与气候相关的不对称基因交换的证据

古代基因渗入可能是影响许多分类群进化和多样化的遗传变异的重要来源。在这里，我们估计了同一部分（Quercus sect. Quercus）中两个远缘橡树物种之间基因流动的时间、方向和程度。我们通过测序数据使用基因分型估计了这些人口统计事件，这些数据为 24 名加州灌木橡树 (Quercus berberidifolia) 和 23 名英格曼橡树 (Quercus engelmannii) 个体产生了 25 702 个单核苷酸多态性。我们使用基于扩散近似的种群遗传推断框架和 Python 包 DaDi 的模型测试方法测试了几种涉及这些物种之间基因流动的场景。我们发现最可能的人口统计情景包括 Q 的瓶颈。engelmannii 与从 Q. berberidifolia 到 Q. engelmannii 的不对称基因流一致。鉴于这种基因流动的时间与加利福尼亚植物区地中海型气候的出现相吻合，我们提出，降水模式和季节性的变化可能有利于气候相关基因从地方性基因渗入到非地方性基因中。加州橡木。