Data from: Body mass-corrected molecular rate for bird mitochondrial DNA

Mitochondrial DNA is still one of the most widely used molecular marker to reconstruct small scale bird phylogeny and phylogeography. It has been proposed that bird mitochondrial genome are evolving under a constant rate of ~0.01 substitution per site per Million years. A large number of studies on bird mitochondrial phylogeny are often associated with molecular dating applying this convenient molecular clock. However, the rate of mitochondrial evolution have repeatedly been shown to vary among species of birds. This variation is not random but is correlated with life-history traits such as body-mass and sexual maturity. As a consequence, the use of a strict molecular clock could systematically biased the molecular dating. In this study, we proposed to used the relationship between body-mass and the rate of molecular evolution to provide a simple method to estimate the substitution rate according to birds body-mass. Using the complete or nearly mitochondrial genome of 475 species, we found a strong relationship between body-mass and neutral substitution rates (R² ~ 0.45 - 0.60). We also report a slight, but significant, variation of the neutral substitution rates among mitochondrial protein-coding genes. Finally, we re-analysed two recently published datasets in order to illustrate the principle of our method. In one case, we obtained molecular dates that are two times older than the estimation obtained using the classical molecular clock. We hope that the corrected molecular clocks we provide will increase the accuracy of future molecular dating studies in birds.