Genetic variation at ribosomal genes supports the existence of two different European subspecies in the megrim Lepidorhombus whiffiagonis

Samples of common megrim (Lepidorhombus whiffiagonis) caught in six different areas in Atlantic and Mediterranean waters were genetically analysed for variation at one mitochondrial gene, 16S rDNA, and one nuclear locus, 5S rDNA. Differences between regions for both genes at sequence level support the existence of two differentiated subspecies totally isolated at genetic level, one in the Mediterranean Sea and other in the Atlantic Ocean. The Strait of Gibraltar and/or the Oran-Almeria Front probably represent an impassable barrier for this species. The results are discussed in the context of the existence of genetic population substructure in marine fish species.