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Research article - Peer-reviewed, 2022

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

Liu, Shuyu; Zhang, Lei; Sang, Yupeng; Lai, Qiang; Zhang, Xinxin; Jia, Changfu; Long, Zhiqin; Wu, Jiali; Ma, Tao; Mao, Kangshan; Street, Nathaniel R.; Ingvarsson, Par K.; Liu, Jianquan; Wang, Jing


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. 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. We observe a high frequency of contemporary hybridization and confirm that multiple previously ambiguous species are in fact F-1 hybrids. Seven species were identified, which experienced different demographic histories that resulted in strikingly varied efficacy of selection and burdens of deleterious mutations. 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. 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. Our results, therefore, illustrate that demography and recombination have interplayed with both positive and negative selection in determining the genomic evolution after hybridization.


hybridization; genetic load; natural selection; adaptive introgression; Populus

Published in

Molecular Biology and Evolution
2022, volume: 39, number: 2, article number: msac008

Authors' information

Liu, Shuyu
Sichuan University
Zhang, Lei
Sichuan University
Sang, Yupeng
Sichuan University
Lai, Qiang
Sichuan University
Zhang, Xinxin
Sichuan University
Jia, Changfu
Sichuan University
Long, Zhiqin
Sichuan University
Wu, Jiali
Sichuan University
Ma, Tao
Sichuan University
Mao, Kangshan
Sichuan University
Street, Nathaniel R.
Umea University
Swedish University of Agricultural Sciences, Department of Plant Biology
Liu, Jianquan
Sichuan University
Wang, Jing
Sichuan University

UKÄ Subject classification

Agricultural Science
Evolutionary Biology

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