Possible mechanisms of mitochondrial gene rearrangement in Continenticola estimated using CREx, with reference to phylogenetic relationships. On the left-hand side, phylogenetic tree obtained from Maximum likelihood and Bayesian analysis of the concatenated dataset for the protein-coding and rRNA genes within mitochondrial genomes; numbers at nodes indicate support values (pp/bs); Asterisks (*) indicate that bootstrap is not applicable to these nodes because of different topologies of trees generated by BI and ML methods. Pink lines connect species that share the same gene order. On the right-hand side, changes of gene order in mitochondrial genomes in several species of triclad; protein-coding genes in blue, tRNA genes in white, rRNA genes in grey; lines with different colours indicate transpositions of different genes; red lines indicate tandem duplication random loss (TDRL) events between species, while the orange colour indicates where TDRL events occurred.