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.杂交带为研究自然环境下选择与基因流的作用提供了理想契机。本研究采用核微卫星（nuclear microsatellites，即单序列重复SSR）与候选基因单核苷酸多态性标记（SNPs），对北美西部纬度跨度40°–60°、海拔跨度350–3500米的白云杉（*Picea glauca*）×恩格尔曼云杉（*P. engelmannii*）杂交带的遗传结构及种间基因流模式进行了表征。研究结果显示，该杂交带分布范围广阔且结构复杂，祖先成分占比跨度大，种间杂合度较低；其形成受不对称的高级世代渐渗作用驱动，且亲本物种间的生殖隔离较弱。基于地理变量的渐变群变异、位点间渐变群的不一致性，以及杂交带的宽度，均表明环境选择维持了物种的遗传完整性。地理渐变群与基因组渐变群的一致性表明，渐变群较窄的位点受到较强的选择作用：这些位点要么偏向于某一亲本物种（定向选择），要么对杂种有利（超显性），这与降雪量、年平均气温等气候变量紧密相关。由过往种群历史事件（通过等位基因丰富度及杂合度相对于平均渐变群中心的偏移得以证实）导致的渐变群位移，或可解释本研究中发现的渐渗不对称性以及恩格尔曼云杉的优势地位。本研究结果为阐明该杂交带的遗传结构及基因混合的精细格局提供了新认知，并鉴定出可能参与物种间生殖隔离的位点。