Author contributions
W. G. and G. H. supervised and designed the research. WZ. L. conducted field investigation and sample collection. WZ. L., JG. X. and H. Z. carried out the lab work. WZ. L., HH. K., W. G., and PW. F. analyzed the genomic data. WZ. L., PW. F. and W. G. discussed the results and wrote the manuscript. All authors read and agree with the manuscript.