Author contributions
Haidong Li conceived and designed the research, Yannan Xu helped to
improve the hypothesis, Chengrui Liao wrote the paper, Haidong Li,
Chengrui Liao and Guoping Lv carried out the field work and the
analysis, Meirong Tian, Jiarong Tian, Huihui Shi and Yannan Xu
contributed to the discussion, and paper revision. (All photos were
photographed by Haidong Li in this article).