Analysis of selective constraints on mitochondrial DNA, Flight ability and physiological index on avian

For most of the birds in the word, they can be divided into two main groups, i.e. resident birds and migratory ones. Most of the energy required for long-distance migration is supplied by mitochondria via oxidative phosphorylation. Therefore, the evolutionary constraints acted on the mitochondria DNA (mtDNA) are considered to vary with the locomotive abilities and flight speed. The flight speed is assumed to increase with mass and wing loading according to the fundamental aerodynamic theories, which is common between aves and aircrafts. We compared 148 avian mitochondrial genomes and main physiological parameters. More nonsynonymous nucleotide substitutions than synonymous ones are accumulated in low-speed and flightless birds rather than high-speed flying birds. No matter how the speed is obtained, directly measured or estimated through physiological index. Our results demonstrated that, besides artificial and environmental factors, selective constraints relevant to flight ability play an essential role in the evolution of mtDNA, even it might cause the extinction of avian species.