Molecular phylogeny of grey mullets based on mitochondrial DNA sequence analysis: Evidence of a differential rate of evolution at the intrafamily level

The phylogeny of the grey mullets is considered problematic both at the intra- and interfamily level. Such a difficulty arises from the highly homogeneous morphology displayed by this group of fish and, consequently, from the paucity of the key morphological characters suitable to address their phylogeny and evolution. In the present work, we have approached the phylogenetic and evolutionary relationships of seven species of Mugilidae, six of which from the Mediterranean Sea, on the basis of the DNA sequences of two mitochondrial genes (cytochrome b and 12S rRNA). Despite the morphological homogeneity exhibited by the taxa considered, the two species of the genus Mugil (M. cephalus and M. curema) showed a remarkable genetic divergence compared to all the other members of the family. The relative rate test revealed a significantly higher rate of evolution along the Mugil lineage.