Identification of the most informative regions of the mitochondrial genome for phylogenetic and coalescent analyses

Analysis of complete mitochondrial genome sequences is becoming increasingly common in genetic studies. The availability of full genome datasets enables an analysis of the information content distributed throughout the mitochondrial genome in order to optimize the research design of future evolutionary studies. The goal of our study was to identify informative regions of the human mitochondrial genome using two criteria: (1) accurate reconstruction of a phylogeny and (2) consistent estimates of time to most recent common ancestor (TMRCA). We created two series of datasets by deleting individual genes of varied length and by deleting 10 equal-size fragments throughout the coding region. Phylogenies were statistically compared to the full-coding-region tree, while coalescent methods were used to estimate the TMRCA and associated credible intervals. Individual fragments important for maintaining a phylogeny similar to the full-coding-region tree encompassed bp 577-2122 and 11,399-16,023, including all or part of 12S rRNA, 16S rRNA, ND4, ND5, ND6, and cytb. The control region only tree was the most poorly resolved with the majority of the tree manifest as an unresolved polytomy. Coalescent estimates of TMRCA were less sensitive to removal of any particular fragment(s) than reconstruction of a consistent phylogeny. Overall, we discovered that half the genome, i.e., bp 3669-11,398, could be removed with no significant change in the phylogeny (pAU = 0.077) while still maintaining overlap of TMRCA 95% credible intervals. Thus, sequencing a contiguous fragment from bp 11,399 through the control region to bp 3668 would create a dataset that optimizes the information necessary for phylogenetic and coalescent analyses and also takes advantage of the wealth of data already available on the control region.