Figure 4
Mcdonald–Kreitman tests on the 13 protein coding regions of the mitogenome among porpoise subgroups. (a) Neutrality index (NI) estimated using the orca as outgroup. (b) NI distributions per mitochondrial lineages, calculated using various outgroups, including orca and all possible interspecific comparisons. The letters on the right of the boxplots indicate significant differences in the mean NI between the different lineages (i.e. boxplot with different letters are statistically different from one another). The red dashed lines represent the limit at which NI reflects positive (NI < 1), neutral (NI = 1), or purifying (NI > 1) selection. NS not significant. The acronyms are provided in Fig. 1.
