Fig. 5
Reconstructed most parsimonious chromosomal rearrangement history of the D. subobscura species subgroup. Shown are the continental lineage (brown) leading to D. subobscura, and the two derived island lineages (blue) D. guanche and D. madeirensis. The inferred ancestral chromosomal arrangement configuration of the subgroup is shown at the root. Arrangements at the terminal nodes can be fixed (black), polymorphic (green) or extinct (red). Worth to mention is the case of Oms. This arrangement was previously known as Og, because, based on cytogenetic evidence, it was thought to have originated in the lineage of D. guanche. The breakpoint sequence synteny analysis conducted herein, however, indicates that the arrangement originated in the mainland before the split of D. madeirensis, where it became fixed, and D. subobscura, where superimposed on it originated separately inversions 4 and ST, and then became extinct. Accordingly, D. subobscura presently polymorphic O inversions 4 and ST may be more appropriately referred to Oms + 4 and Oms + ST, rather than O3 + 4 and OST, because arrangement 3 is ancestral to ms