Dong, Y., S. Chen, S. Cheng, W. Zhou, Q. Ma, Z. Chen, C.-X. Fu, X. Liu, Y. Zhao, P. S. Soltis, G. K.-S. Wong, D. E. Soltis, and Q.-Y. Xiang. 2019. Natural selection and repeated patterns of molecular evolution following allopatric divergence. eLife 8. [View on Publisher’s site]


Although geographic isolation is a leading driver of speciation, the tempo and pattern of divergence at the genomic level remain unclear. We examine genome-wide divergence of putatively single-copy orthologous genes (POGs) in 20 allopatric species/variety pairs from diverse angiosperm clades, with 16 pairs reflecting the classic eastern Asia-eastern North America floristic disjunction. In each pair, >90% of POGs are under purifying selection, and <10% are under positive selection. A set of POGs are under strong positive selection, 14 of which are shared by 10–15 pairs, and one shared by all pairs; 15 POGs are annotated to biological processes responding to various stimuli. The relative abundance of POGs under different selective forces exhibits a repeated pattern among pairs despite an ~10 million-year difference in divergence time. Species divergence times are positively correlated with abundance of POGs under moderate purifying selection, but negatively correlated with abundance of POGs under strong purifying selection.