On the other hand, owing to the occurrence of a series of climatic oscillations and geographic events in the past 65 Mya [12], [13], [23]–[25], plants not only experienced expansion and contraction of their ranges [26]–[30], but also diversified to adapt to new niches [31]–[35]. It may explain why Wing [36] detected a mixture of tropical and temperate elements in the Eocene floras of the Rocky Mountains. Lavin & Luckow [37] and Wen [38] proposed that the study of disjunctions in temperate groups should include their subtropical and tropical relatives, and vice versa.