Barriers to gene flow play an important role in miantaining reproductive isolation between two closely relatedPopulus(Salicaceae) species

AbstractIn most species, natural selection plays a key role in genomic heterogeneous divergence. Additionally, barriers to gene flow, such as chromosomal rearrangements or gene incompatibilities, can cause genome heterogeneity. We used genome-wide re-sequencing data from 27Populus albaand 28P. adenopodaindividuals to explore the causes of genomic heterogeneous differentiation in these two closely related species. In highly differentiated regions, neutrality tests (Tajima’s D and Fay & Wu’s H) revealed no difference while the absolute divergence (dxy) were significantly higher than genome background, which indicates that natural selection did not play a major role but barriers to gene flow play an important role in generating genomic heterogeneous divergence and reproductive isolation. The two species diverged ∼5-10 million years ago (Mya), when the Qinghai-Tibet Plateau reached a certain height and the inland climate of the Asian continent became arid. We further found some genes that are related to reproduction.