如果自然选择强于抵消基因流和漂移,则性状和基础基因座的适应性分化可以在较小的地理范围内发生。我们使用耦合的定量遗传和基因组方法对风授粉的树种进行了研究,红木槲树,沿着陡峭的,苏必利尔湖海岸的狭窄梯度,包括100公里内的四个美国农业部硬区。对于这项研究的定量遗传成分,我们检查了一个普通花园中八个种群的表型分化,测量种子质量,发芽,高度,阀杆直径,叶数,特定的叶面积和存活率。对于基因组成分,我们使用RAD-seq量化了来自同一地区的26个种群的遗传分化。因为与椭球棘的杂交发生在物种范围的其他部分,我们纳入了这种同源物的两个群体进行比较。在普通的花园书房里,我们发现了一个强烈的群体分化信号,该信号与10个测量性状中的9个中的至少一个气候因素显着相关。相比之下,我们没有发现基于FST或任何其他指标的群体间基因组分化的证据.然而,基于距离和基因型-环境关联分析确定了显示选择特征的基因座,在五个分析中有一个共同的位点。该位点与最冷月份的最低温度有关,一个定义气候带的因素,在常见的花园分析中也很重要。此外,我们记录了从Q.椭圆角向Q.rubra的渗入,渗入率与气候梯度相关。总之,这项研究揭示了与气候适应相一致的数量性状和基因组水平的选择特征,一种在更广泛的地理范围内更常见的模式,尤其是在长寿的风授粉物种中。
Adaptive differentiation of traits and underlying loci can occur at a small geographical scale if natural selection is stronger than countervailing gene flow and drift. We investigated this hypothesis using coupled quantitative genetic and genomic approaches for a wind-pollinated tree species, Quercus rubra, along the steep, narrow gradient of the Lake Superior coast that encompasses four USDA Hardiness Zones within 100 km. For the quantitative genetic component of this study, we examined phenotypic differentiation among eight populations in a common garden, measuring seed mass, germination, height, stem diameter, leaf number, specific leaf area and survival. For the genomic component, we quantified genetic differentiation for 26 populations from the same region using RAD-seq. Because hybridisation with Quercus ellipsoidalis occurs in other parts of the species\' range, we included two populations of this congener for comparison. In the common garden study, we found a strong signal of population differentiation that was significantly associated with at least one climate factor for nine of 10 measured traits. In contrast, we found no evidence of genomic differentiation among populations based on FST or any other measures. However, both distance-based and genotype-environment association analyses identified loci showing the signature of selection, with one locus in common across five analyses. This locus was associated with the minimum temperature of the coldest month, a factor that defines the climate zones and was also significant in the common garden analyses. In addition, we documented introgression from Q. ellipsoidalis into Q. rubra, with rates of introgression correlated with the climate gradient. In sum, this study reveals signatures of selection at the quantitative trait and genomic level consistent with climate adaptation, a pattern that is more often documented at a much broader geographical scale, especially in long-lived wind-pollinated species.