Nucleotide divergence among specimens along the mitogenome of Ma. balthica . Top: boundaries of protein-coding genes (black) and ribosomal genes (grey). Haplotypes H1-H5 represent cox1 haplotypes (see Methods). Vertical bars represent the position of non-synonymous mutations for the four cox1 haplotype comparisons, (a) divergence as measured by the Tamura and Nei  model of nucleotide substitution (TN93; substitution/site) and πA/πS ratio for (b) all six mtDNA and (c) the Ma. balthica rubra lineage (n = 5 mtDNA).