Mitochondrial insertions into primate nuclear genomes suggest the use of numts as a tool for phylogeny

Homoplasy-free characters are a valuable and highly desired tool for molecular systematics. Nuclear sequences of mitochondrial origin (numts) are fragments of mitochondrial DNA that have been transferred into the nuclear genome. numts are passively captured into genomes and have no transposition activity, which suggests they may have utility as phylogenetic markers. Here, five fully sequenced primate genomes (human, chimpanzee, orangutan, rhesus macaque, and marmoset) are used to reconstruct the evolutionary dynamics of recent numt accumulation in a phylogenetic context. The status of 367 numt loci is used as categorical data, and a maximum parsimony approach is used to trace numt insertions on different branches of the taxonomically undisputed primate phylogenetic tree. The presence of a given numt in related taxa implies orthologous integration, whereas the absence of a numt indicates the plesiomorphic condition prior to integration. An average rate of 5.65 numts per 1 My is estimated on the tree, but insertion rates vary significantly on different branches. Two instances in which the presence-absence pattern of numts does not agree with the phylogenetic tree were identified. These events may be the result of either lineage sorting or reversal. Using the numts reported here to reconstruct primate phylogeny produces the canonical primate tree topology with high bootstrap support. Moreover, numts identified in gorilla Supercontigs were used to test the human-chimp-gorilla trichotomy, yielding a high level of support for the sister relationship of human and chimpanzee. These analyses suggest that numts are valuable phylogenetic markers that can be used for molecular systematics. It remains to be tested whether numts are useful at deeper phylogenetic levels.