Hotspots of structural polymorphism that drive the diversification of organelle genomes. The phylogenetic tree on the left was based on whole-genome alignment of the seven complete mt genomes. (A) Structural and sequence polymorphism of inverted repeat in the pt genomes. (B) Structural and sequence polymorphism of the hotspot in the mt genomes. Within each sub-figure, genomic features were drawn proportionally to their actual length. Grey solid lines, inserted for alignment purposes, were not actual sequences.