Cytochrome b sequence divergence in the European sea bass (Dicentrarchus labrax) and phylogenetic relationships among some Perciformes species

The entire cytochrome b (cyt b) gene has been sequenced in eight Mediterran ean populations of the European sea bass, Dicentrarchus labrax and in one o f D. punctatus. Our data indicate that both eastern (Greece and Egypt) and northwestern (French coast) populations of D. labrax were genetically diffe rentiated from the Tyrrhenian ones, which were nearly indistinguishable fro m each other at the cyt b level. The D. labrax population from the Atlantic coast (Portugal) was genetically quite distinct from all the Mediterranean ones. These results strongly confirm the conclusions from previous studies where the same populations were screened for allozymes, random amplified p olymorphic DNA (RAPD) and mitochondrial DNA (mtDNA) D-loop variation. Seven other species of Perciformes belonging to five different families (Sparida e, Serranidae, Carangidae, Pomatomidae, Sciaenidae) were sequenced to explo re the usefulness of the cyt b gene for inferring evolutionary relationship s at different hierarchical levels. The data were analysed together with ot her published cyt b sequences from Perciformes fishes. Our data suggest tha r the superfamily Percoidea is not monophyletic. At the family level, the S paridae and Moronidae seem to be monophyletic. The evolutionary relationshi ps among families were not resolved. Possible causes for this lack of resol ution are discussed.