Fig. 2

Empirical distributions of the abundance of repeat sequences with lengths from 5 to 8 bp. The abundance of direct and inverted repeats in the 221 mitogenomes, and their comparison with the abundance of repeats in randomized DNA sequences, each figure is an independent analysis for a specific size of repeat sequences. Each point in the distributions represent an organism and the average number of repeats per Kbp. a Empirical distributions of repeat sequences of 5 bp, b Empirical distributions of repeat sequences of 6 bp, c Empirical distributions of repeat sequences of 7 bp and (d) Empirical distributions of repeat sequences of 8 bp. To review the distributions of sizes from 5 to 20 bp go to Additional file 2. (Abbreviations used in the figure are interpreted as follows DRs: Direct Repeat sequences; IRs: Inverted Repeat sequences; DRs-rn: Random Direct Repeat Sequences; IRs-rn: Random Inverted Repeat Sequences; RS/Kbp: Number of repeat sequences divided by the mitogenome size in kilobase pairs)