A DIVALIKE was found to be the best-fitting model (Table 2). The ARE for Coptis using BioGeoBEARS is indicated in Fig. 3 and Additional file 2: Figure S1. Area probabilities of all nodes are high except the root. Our ARE shows that the ancestral range of Coptis and Xanthorhiza is unresolved but likely involved eastern North America, western North America and Japan (node 1). The most recent common ancestor of Coptis was likely distributed in western North America, southern East Asia and Japan (node 2). Within Coptis, two vicariance events and two dispersal events were inferred at the species level (Fig. 3).Table 2Comparison of the fit of three models of biogeographical range evolution and model-specific estimates for the different parametersModelLnLParameter nb d e AICΔAICAICCΔAICCDEC−24.0620.031.00 × 10− 1252.123.5953.043.58DIVALIKE−22.2720.031.00 × 10− 1248.53049.460BAYAREALIKE−28.7720.041.04 × 10−161.5513.0252.4713.01d = dispersal rate; e = extinction rateFig. 3Ancestral range estimation (ARE) for Copits BEAST using BioGeoBEARS under the DIVALIKE model. Labeled nodes (1 to 5, as referred to Fig. 2), with 95% highest posterior densities (grey bars), are discussed in the text. The estimated ancestral ranges with the highest ML probability are shown by boxes on each node. Additional file 2: Figure S1 provides all ARE per node with pies. A pie is placed in this figure at the root with the highest probability less than 50%. The depictions of temperature (in red) and sea level (in black) changes are modified from Zachos et al.  and Haq et al. , respectively. Plio., Pliocene; Plt., Pleistocene