Allozyme variation and genetic inter-relationships between seven flatfish species (Pleuronectiformes)

A total of 11 enzymes coded by 14 loci were assayed for each of 17 populati ons (from the north east Atlantic and Mediterranean) of seven flatfish spec ies, including representatives of three of the four European families of th e order Pleuronectiformes. Diagnostic alleles were observed for each specie s and there were fixed differences between the species at many loci. Thus a ll species were genetically distinct, although there were some common allel es. Hobs was higher than the average of a range of fish species and was als o higher than that of vertebrate species as a whole. It seems that flatfish as a group may show higher levels of genetic variation than other fish. Va lues of genetic identity for all pairwise comparisons fell comfortably with in the ranges expected. The data support the grouping of plaice and flounde r into a single genus, Pleuronectes, but it is concluded that the retention of the dab in a separate genus, Limanda, is justified. A high level of gen etic divergence was found between Dover and thickback soles. Genetic diverg ence data support the hypothesis that Pleuronectes flesus luscus in the Aeg ean Sea is a distinct subspecies of Pleuronectes flesus (flounder). The dat a show a clear separation of the Mediterranean Dover sole population from t hose in the Atlantic. Low genetic divergence was observed between the Aegea n Sea and Atlantic brill populations. It is speculated that about 5 Mya the families Pleuronectidae and later Soleidae evolved from the ancestral Scop hthalmidae. (C) 2001 The Linnean Society of London.