Data from: Genetic architecture and genomic patterns of gene flow between hybridizing species of Picea

Hybrid zones provide an opportunity to study the effects of selection and gene flow in natural settings. We employed nuclear microsatellites (single sequence repeat (SSR)) and candidate gene single-nucleotide polymorphism markers (SNPs) to characterize the genetic architecture and patterns of interspecific gene flow in the Picea glauca × P. engelmannii hybrid zone across a broad latitudinal (40–60 degrees) and elevational (350–3500 m) range in western North America. Our results revealed a wide and complex hybrid zone with broad ancestry levels and low interspecific heterozygosity, shaped by asymmetric advanced-generation introgression, and low reproductive barriers between parental species. The clinal variation based on geographic variables, lack of concordance in clines among loci and the width of the hybrid zone points towards the maintenance of species integrity through environmental selection. Congruency between geographic and genomic clines suggests that loci with narrow clines are under strong selection, favoring either one parental species (directional selection) or their hybrids (overdominance) as a result of strong associations with climatic variables such as precipitation as snow and mean annual temperature. Cline movement due to past demographic events (evidenced by allelic richness and heterozygosity shifts from the average cline center) may explain the asymmetry in introgression and predominance of P. engelmannii found in this study. These results provide insights into the genetic architecture and fine-scale patterns of admixture, and identify loci that may be involved in reproductive barriers between the species.杂交带为探究自然环境下选择与基因流的效应提供了绝佳研究契机。本研究利用核微卫星（nuclear microsatellites，单序列重复标记，SSR）与候选基因单核苷酸多态性标记（single-nucleotide polymorphism markers，SNPs），对北美西部纬度跨度40°–60°、海拔范围350–3500米的白云杉（Picea glauca）×恩氏云杉（P. engelmannii）杂交带的遗传结构与种间基因流模式进行了系统表征。 研究结果显示，该杂交带分布范围广、结构复杂，种群祖先组分分布宽泛，种间杂合度较低；其形成受不对称多世代渐渗作用塑造，且亲本物种间的生殖隔离程度较低。基于地理变量的渐变变异、位点间渐变模式一致性的缺失，以及杂交带的整体宽度，均表明环境选择维持了物种的遗传完整性。 地理渐变模式与基因组渐变模式间的一致性显示，梯度跨度较窄的位点受到强烈选择压力：这类位点要么偏向单一亲本物种（定向选择），要么对杂交后代具有优势（超显性），这与降雪量、年平均气温等气候变量存在强关联。 由过往种群历史事件引发的梯度位移（通过偏离平均梯度中心的等位基因丰富度与杂合度变化得以佐证），或可解释本研究中观察到的渐渗不对称性以及恩氏云杉占优势的现象。 本研究结果为遗传结构与基因混合的精细模式提供了新的认知，并鉴定出可能参与物种间生殖隔离的遗传位点。