Author contributions
QW, JW and HZ collected samples. WW and YZ extracted DNA and RNA for sequencing. QW, XR and YH carried out genome assembly and assessment, and performed gene prediction and annotation. PL, JTL and JJL carried out comparative genome analysis. QW and JL performed selection signature analysis. JL and YH conceived this project. QW and XR wrote the manuscript. All authors contributed to the final manuscript editing.