Relaxation of selective constraints on avian mitochondrial DNA following the degeneration of flight ability

The evolution of flight is the most important feature of birds, and this ability has helped them become one of the most successful groups of vertebrates. However, some species have independently lost their ability to fly. The degeneration of flight abilit

Special thanks to Dr. David Irwin, Dr. R. W. Murphy, Scott Groom, Jing He, and two anonymous reviewers for helpful comments. This work was supported by grants from National Basic Research Program of China (973 Program, 2007CB411600), National Natural Scie