In clade I, one vicariance episode happened between western North America and southern East Asia in the Late Miocene (ca. 7.78 Ma, 95% HPD: 5.16–10.52; node 3), which overlapped closely with the time of the first opening of the Bering Strait (7.4–5.5 Ma) . Evidence from sedimentology and foraminifera indicates that uplift of the St. Elias Mts. in Alaska began about 8.5 Ma . Palynological analyses suggest that the trends of temperature decline and increasing canopy openness in Alaska and Yukon Territory occurred between 9.7 and 7.0 Ma, owing to global and local tectonic developments . These events may explain the distribution of Coptis between southern East Asia and western North America during the Late Miocene. The split of western North American Polypodium californicum Kaulf. (Polypodiaceae) and its eastern Asian relatives (P. fauriei (Copel.) Makino & Nemoto and P. glycyrrhiza D.C. Eaton) also occurred during the same period (ca. 8.81 Ma, 95% HPD: 5.06-13.08) . Such distribution patterns resulting from orogenic events have been found in some plant lineages and in different biomes, such as Campanulaceae , Orchidaceae , and Rubiaceae .