RFLP analysis of mitochondrial DNA to evaluate genetic variation in striped red mullet (Mullus surmuletus L.) and red mullet (Mullus barbatus L.) populations

The genetic differentiation of striped red:mullet (Mullus surmuletus) and r ed mullet (Mullus barbatus) was investigated in 6 Mediterranean populations of each species by means of restriction fragment length polymorphism analy sis of mitochondrial DNA. Three segments amplified by polymerase chain reac tion (control region, COI, and 12S-16S ribosomal RNA) were digested with 20 restriction endonucleases, revealing 71 haplotypes for M. surmuletus and 3 0 for M. barbatus. For the two species nucleotide diversity was equally dis tributed within and among populations, leading to N-ST values of 0.545 and 0.500 for M. surmuletus and M. barbatus, respectively. However, intrapopula tion and interpopulation genetic structuring appeared to be much higher for M. surmuletus than for M. barbatus (1.88% vs. 0.46% of mean intrapopulatio n nucleotide diversity; 1.94% vs. 0.47% of mean interpopulation nucleotide diversity, 0.055% vs. 0.002% of net interpopulation divergence). Furthermor e, 81.69% of the haplotypes observed;for M. surmuletus were unique, whereas 70.29% of M. barbatus individuals,were grouped in 3 common haplotypes. Giv en that fishing pressure and population sizes are similar for both species, this differentiation could be attributed to differences in biological para meters and life histories between the two species, coupled with oceanograph ic conditions prevailing in the studied area.