Fig. 1
Expected mitochondrial gene rearrangement under different evolutionary scenarios. a Tandem duplication–random loss model (TDRL): A, N, OL, C were tandem duplicated, followed by random loss of the redundant copies. Random loss could occur repeatly, resulting in alternative loss types [5]. b Tandem duplication and non-random loss (TDNL), or dimer-mitogenome and non-random loss (DMNL) models: a dimeric molecule was formed by two monomers linked head-to-tail, then one of the two sets of promoters lost function, and genes with the same polarity would cluster together [9, 10]. c Inter- or intra-mtDNA recombination: duplication was caused by unequal crossing over of intermolecular recombination. Redundant copies were then deleted. Intramolecular recombination could cause concerted evolution of the two copies of trnA [12]. d Double replications and random loss (DRRL) model: the CR was duplicated and translocated, then double replications of the mitogenome were successively initiated from the two CRs, leading to the duplication of the genes between the two CRs, followed by random loss [13]. Underline indicates the transcriptional direction of L-strand–encoding gene. “---” represents other coding gene. “-”, pseudogenes or noncoding sequence. Gray boxes represent the genes involved in rearrangement