Structural rearrangements, including parallel inversions, within the chloroplast genome of Anemone and related genera

Chloroplast DNA cleavage sites for 10 restriction enzymes were mapped for 46 species representing all sections of Anemone, four closely related genera (Clematis, Pulsatilla, Hepatica, and Knowltonia), and three more distantly related outgroups (Caltha, Ranunculus, and Adonis). Comparison of the maps revealed that the chloroplast genomes of Anemone and related genera have sustained an unusual number and variety of rearrangements. A single inversion of a 42-kb segment was found in the large single-copy region of Adonis aestivalis. Two types of rearrangements were found in the chloroplast genome of Clematis, Anemone, Pulsatilla, Hepatica, and Knowltonia: An approximately 4-kb expansion of the inverted repeat and four inversions within the large single-copy region. These rearrangements support the monophyletic status of these genera, clearly separating them from Caltha, Ranunculus, and Adonis. Two further inversions were found in two Clematis species and three Anemone species. While appearing to support a monophyletic grouping for these taxa, these two inversions conflict with data from both chloroplast restriction sites and morphology and are better interpreted as having occurred twice independently. These are the first two documented cases of homoplastic inversions in chloroplast DNA. Finally, the second intron of the chloroplast rps 12 gene was shown to have been lost in the common ancestor of the same three Anemone species that feature the two homoplastic inversions.