Demographic History and Natural Selection Shape Patterns of Deleterious Mutation Load and Barriers to Introgression across Populus Genome

第一作者：Shuyu Liu

第一单位：四川大学

通讯作者：Jing Wang

 Abstarct 

背景+问题：Hybridization and resulting introgression are important processes shaping the tree of life and appear to be far more common than previously thought. However, how the genome evolution was shaped by various genetic and evolutionary forces after hybridization remains unresolved. 

杂交及由此导致的渐渗（introgression）是塑造生命之树的重要进程，并且似乎要比以前所认为的要普遍得多。然而，杂交后各种遗传和演化力量如何塑造基因组的演化还不清楚。

主要研究：Here we used whole-genome resequencing data of 227 individuals from multiple widespread Populus species to characterize their contemporary patterns of hybridization and to quantify genomic signatures of past introgression. 

本文中，作者通过对广泛分布的227份杨树种质进行全基因组重测序，以此来解析杂交的当代模式，并定量渐渗后的基因组特征。

结果1：We observe a high frequency of contemporary hybridization and confirm that multiple previously ambiguous species are in fact F1 hybrids. Seven species were identified, which experienced different demographic histories that resulted in strikingly varied efficacy of selection and burdens of deleterious mutations. 

作者发现，当代的杂交频率较高，并确认了多个先前分类不明确的物种其实就是F1代的杂种。作者共鉴定出七个物种，它们经历了不同的种群动态演化历史，导致了显著不同的选择效率以及有害突变负荷。

结果2：Frequent past introgression has been found to be a pervasive feature throughout the speciation of these Populus species. The retained introgressed regions, more generally, tend to contain reduced genetic load and to be located in regions of high recombination. 

在这些杨属物种的物种形成过程中，渐渗是一个较为普遍的特征。保留下来的渐渗区往往包含更低的遗传负荷，并位于重组率较高的区域。

结果3：We also find that in pairs of species with substantial differences in effective population size, introgressed regions are inferred to have undergone selective sweeps at greater than expected frequencies in the species with lower effective population size, suggesting that introgression likely have higher potential to provide beneficial variation for species with small populations. 

作者还发现，在有效种群大小存在显著差异的一对物种中，相比于有效种群大小较小的物种，在有效种群大小较大的物种中渐渗区域经历的选择清除频率更高，这表明渐渗对于小群体来说具有更大的潜力提供有益的变异。

结论：Our results, therefore, illustrate that demography and recombination have interplayed with both positive and negative selection in determining the genomic evolution after hybridization.

因此，作者的研究结果表明，群体动态和遗传重组同时与正选择和负选择相互作用，决定着在杂交后的基因组演化。

** 王婧 **

doi: https://doi.org/10.1093/molbev/msac008

Journal: Molecular Biology and Evolution

Published date: February 03, 2022