The maximum clade credibility tree of B. flavescens and their closely related species, reconstructed with *BEAST from gene trees for the COI, 16S, and PEPCK genes and calibrated using estimate time from Hines (2008). The MCMC chains were run for 500 million generations, sampled every 5000th generation. Burn-in fraction is 20%. The posterior probabilities are shown under the nodes. Blue bars represent the 95% confidence limits on the estimate dates of divergence. Bombus lepidus is the outgroup.