Tandem duplication followed by random loss (TDRL) is the most frequently invoked model to explain the diversity of gene rearrangements in metazoan mitogenomes. The initial stages of gene rearrangement are difficult to observe in nature, which limits our understanding of incipient duplication events and the subsequent process of random loss. Intraspecific gene reorganizations may represent intermediate states, and if so they potentially shed light on the evolutionary dynamics of TDRL.
Nucleotide sequences in a hotspot of gene-rearrangement in 28 populations of a single species of frog, Quasipaa boulengeri, provide such predicted intermediate states. Gene order and phylogenetic analyses support a single tandem duplication event and a step-by-step process of random loss. Intraspecific gene rearrangements are not commonly found through comparison of all mitochondrial DNA records of amphibians and squamate reptiles in GenBank.
The intraspecific variation in Q. boulengeri provides insights into the rate of partial duplications and deletions within a mitogenome, and reveals that fixation and gene-distribution in mitogenomic reorganization is likely non-adaptive.