We build phylogenies for those genes and revealed they seems to have been duplicated at the same time, in a common ancestor of Oleaceae and their sister family (where distyly has also been reported).

There's more to tell about those genes so I encourage you to check our paper and the GREAT companion paper from Castric et al. in the same issue. They investigate further the functionnality of the system in the olive tribe

The homomorphic self-incompatibility system in Oleaceae is controlled by a hemizygous genomic region expressing a gibberellin pathway gene

The self-incompatibility system of the Oleaceae is unusual, with the long-term maintenance of only two groups of reproductive compatibility. Castric et al. identify a hemizygous chromosomal fragment u...