Figure 4

Evolutionary history of gadiform T-P spacer. Key events in the evolutionary history of the T-P spacer are indicated by numbers 1–4 and explained in the main text. In short: 1, first occurrence of spacer; 2, first occurrence of Box-motif; 3abc, duplication of Box-motif; 4, second duplication of Box motif. Genus containing T-P spacer with heteroplasmic feature is indicated by star (*). The Bregmaceros spacer is involved in gene order rearrangements (#). The 32 gadiform species represent 20 genera and 8 families (color-coded). Pattern of relationship between gadiform families is extrapolated from [38]–[40].