Department of Biology, Texas A&M University, TAMU, College Station, TX, USA.
Centro de Investigaciones Cientıficas de las Huastecas "Aguazarca", Calnali Hidalgo, Mexico.
Mol Ecol Resour. 2021 Oct;21(7):2278-2287. doi: 10.1111/1755-0998.13428. Epub 2021 May 30.
The use of genomic and phenotypic data to scan for outliers is a mainstay for studies of hybridization and speciation. Geographic cline analysis of natural hybrid zones is widely used to identify putative signatures of selection by detecting deviations from baseline patterns of introgression. As with other outlier-based approaches, demographic histories can make neutral regions appear to be under selection and vice versa. In this study, we use a forward-time individual-based simulation approach to evaluate the robustness of geographic cline analysis under different evolutionary scenarios. We modelled multiple stepping-stone hybrid zones with distinct age, deme sizes, and migration rates, and evolving under different types of selection. We found that drift distorts cline shapes and increases false positive rates for signatures of selection. This effect increases with hybrid zone age, particularly if migration between demes is low. Drift can also distort the signature of deleterious effects of hybridization, with genetic incompatibilities and particularly underdominance prone to spurious typing as adaptive introgression. Our results suggest that geographic clines are most useful for outlier analysis in young hybrid zones with large populations of hybrid individuals. Current approaches may overestimate adaptive introgression and underestimate selection against maladaptive genotypes.
利用基因组和表型数据来扫描异常值是研究杂交和物种形成的主要方法。地理渐变分析自然杂交区被广泛用于通过检测与基因渐渗基线模式的偏差来识别选择的可能特征。与其他基于异常值的方法一样，种群历史可能会使中性区域看起来受到选择的影响，反之亦然。在这项研究中，我们使用基于个体的正向时间模拟方法来评估在不同进化场景下地理渐变分析的稳健性。我们模拟了具有不同年龄、居群大小和迁移率的多个阶跃式杂交区，并在不同类型的选择下进化。我们发现，漂变扭曲了渐变形状，并增加了选择特征的假阳性率。这种效应随着杂交区年龄的增加而增加，特别是在居群之间的迁移率较低的情况下。漂变也会扭曲杂交有害影响的特征，遗传不相容性，特别是易位显性，容易被错误地归类为适应性基因渐渗。我们的研究结果表明，地理渐变最适合在具有大量杂交个体的年轻杂交区进行异常值分析。当前的方法可能高估了适应性基因渐渗，低估了对不利基因型的选择。
