Parapatric cryptic speciation in Raja miraletus (L. 1758) species complex inferred from mitochondrial and nuclear markers

The brown skate Raja miraletus is distributed from Mediterranean and North Eastern Atlantic to South Western Indian. A significant variation in mitochondrial DNA led to recognize at least three parapatric clades in the Mediterranean, West and South Africa. Upwelling areas at Cape Blanco (21° N) and at Cape Frio (18° S) were considered as the main geographical barriers. With respect to previous analyses we have currently increased our dataset both in terms of specimens and molecular markers. Specimens were collected from Portugal, Mediterranean, Senegal, Angola and South Africa coasts. We sequenced the mitochondrial coxI gene in 219 individuals and genotyped 8 microsatellite loci in 245 individuals. Parsimony haplotype network and Bayesian clustering analyses were performed. The mitochondrial haplotype analysis clearly showed three clades associated to the main geographical areas: the Portugal-Mediterranean, the Senegal and the Angola-South Africa ones. Moreover within the first clade a separation can be detected between Eastern and Western Mediterranean sub-basins, and within the third clade, Angola and South Africa samples showed both private and shared haplotypes. The Bayesian clustering analysis produced two main groups of Portugal-Mediterranean and African samples. In the first, a further subdivision can be detected between Portugal-Western Mediterranean and Eastern Mediterranean. In the second Senegal and South Africa are clearly assigned to different clusters with specimens from Angola showing admixed genotypes. Results of nuclear data confirm the mitochondrial ones highlighting three parapatric cryptic species, but while Cape Blanco upwelling act as gene flow barrier, Cape Frio is less relevant as previously supposed.