Data from: Landscape genomics of Populus trichocarpa: the role of hybridization, limited gene flow and natural selection in shaping patterns of population structure

Populus trichocarpa is an ecologically important tree across western North
America. We used a large population sample of 498 accessions over a wide
geographical area genotyped with a 34K Populus SNP array to quantify
geographical patterns of genetic variation in this species (landscape
genomics). We present evidence that three processes contribute to the
observed patterns: (1) introgression from the sister species P.
balsamifera (2) isolation-by-distance and (3) natural selection.
Introgression was detected only at the margins of the species’
distribution. Isolation-by-distance was significant across the sampled
area as a whole, but no evidence of restricted gene flow was detected in a
core of drainages from southern British Columbia. We identified a large
number of FST outliers. GO analyses revealed that FST outliers are
overrepresented in genes involved in circadian rhythm and response to
red/far-red light when the entire dataset is considered, while in southern
British Columbia heat response genes are overrepresented. We also
identified strong correlations between geoclimate variables and allele
frequencies at FST outlier loci that provide clues regarding the selective
pressures acting at these loci.

毛果杨（Populus trichocarpa）是北美西部一种具有重要生态意义的树种。我们采用覆盖广泛地理区域的498份种质资源大群体样本，利用34K毛果杨单核苷酸多态性（SNP）芯片进行基因分型，以量化该物种遗传变异的地理模式（景观基因组学）。研究表明，三种过程共同塑造了观测到的模式：（1）来自近缘物种香脂杨（P. balsamifera）的基因渐渗；（2）距离隔离；（3）自然选择。基因渐渗仅在该物种分布范围的边缘区域被检测到。距离隔离在整个采样区域内显著存在，但在不列颠哥伦比亚省南部的核心流域中未发现基因流受限的证据。我们鉴定出大量FST异常位点。基因本体（GO）分析显示，在整个数据集范围内，FST异常位点在参与昼夜节律及红/远红光响应的基因中显著富集；而在不列颠哥伦比亚省南部，热响应基因则呈现富集趋势。此外，我们还发现地理气候变量与FST异常位点的等位基因频率之间存在强相关性，这为揭示作用于这些位点的选择压力提供了线索。