The molecular clock enforced dated phylogram from Bayesian Inference (BI) among fourfold degenerate sites from partial alignments of 2,562 nuclear genes without evidence of positive selection calibrated on fossil data. The Bayes Factor test shows no difference with the clock-enforced tree and clock-non-enforced tree. Blue 95% HPD node bars are filled according to posterior probability. Vertical arrows mark the approximate timing of the opening of the Bering Strait . The scale bars denote time based on two dates of calibration based on the fossil record: 13–19 Ma at node A with 12S mitochondrial sequence (Lee, 2003 rate estimate’)  and 5–12 Ma at node C (‘Fossil’) .
Kober and Bernardi BMC Evolutionary Biology 2013 13:88 doi:10.1186/1471-2148-13-88