Vertebrate Mitochondrial Genome Organization: Evidence of Convergent Evolution

The evolution of the vertebrate mitochondrial genome has been the focus of numerous genetic and evolutionary studies over the last several decades. Initially, sampling was heavily biased toward taxonomic orders of greatest economic or health importance, but recent advances in DNA sequencing technology have facilitated a much broader phylogenetic sampling from which we can clarify general evolutionary trends such as patterns of gene rearrangement. Toward this end, we performed a comparative genomic analysis of the 2,831 vertebrate mitochondrial genomes representing 12 classes that are available in the NCBI database. Using a combination of bioinformatics methods, we determined that there is a great variation in the proportion of rearrangement by gene and by taxonomic class, with higher rates being observed in Reptilia, Amphibia, Petromyzonti, Mammalia, and Actinopteri. Further, within each class, there is large variation in proportion of reorganization among different orders or even taxonomic families. Eleven events of convergence in the genic order among different taxonomic orders were determined, most of them not previously reported.