Convergent evolution of sex chromosomes in two palm species, Phoenix dactylifera and Kerriodoxa elegans

In palms, many dioecious species have emerged from at least eight independent events; the mechanisms of sex determination remain poorly understood. Here, we identify and compare the sex chromosomes of Kerriodoxa elegans with those of the well-studied date palm (Phoenix dactylifera), which evolved dioecy independently from a monoclinous common ancestor.

We developed target sequence capture kits and inferred sex-linked genes using a probabilistic approach in both species.

We find a striking similarity between the sex-linked regions of K. elegans and P. dactylifera, with the majority of sex-linked genes being common between the two species. However, we confirm that these regions evolved independently, much later than the split between the lineages.

This case of convergent evolution seems to be unique in plants so far, and raises questions on the mechanisms of sex determination. This could be explained by the presence of genes related to floral sex development and sex determination in this region, which have been recruited during the evolution of sex chromosomes, even though the genes involved may differ between the two species.