Conceptualization, C.N., G.M.M. and L.M.E.-W.; methodology, C.N.; software, C.N.; validation, C.N.; formal analysis, C.N.; investigation, C.N.; resources, C.N.; data curation, C.N.; writing—original draft preparation, C.N., L.M.E.-W., and G.M.M.; writing—review and editing, L.M.E.-W., G.M.M., W.X., and W.Y.; visualization, C.N.; supervision, G.M.M.; funding acquisition, C.N., W.X., and W.Y. This research was funded by National Science Foundation of China (31570447), program of National Key (cultivating) Disciplines in Central South University of Forestry and Technology, combination program of Plant Biology and Conservation in Northwestern University and Chicago Botanic Garden, and China Scholarship Council (CSC201408430072, awarded to C.N.).