Molecular evidence in Diplotaxis (Brassicaceae) suggests a Quaternary origin of the Cape Verdean flora

In comparison with other Macaronesian Islands (e.g., the Canary Islands), the Cape Verde Islands have received little attention in terms of plant molecular phylogenetic studies, which might also elucidate the general floristic history of this archipelago. The Cape Verdean vascular plant flora (ca. 12% endemics) has traditionally been regarded as relict of a former subtropical Tertiary flora. In contrast, it has been postulated more recently that the flora is much younger and of Pleistocene origin. To test these hypotheses, we have produced molecular phylogenies associated with a molecular clock approach, sampling all nine Cape Verdean endemic Diplotaxis taxa and 21 accessions representing the D. harra complex from across its distributional range. Analyzing three molecular markers from the nuclear and chloroplast genome, we provide evidence that the Cape Verdean endemic Diplotaxis originated from North African D. harra populations in Pleistocene times, putatively linked to the genesis of the (western) Sahara. This adds to the emerging picture that the present Cape Verdean flora is of Pleistocene origin.