Coastal Physical Features in West Africa Shape the Genetic Structure of the Bonga Shad

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3793960/

In this paper the genetic diversity of the fish E. Fimbriata that lives along the west coast of Africa is studied. In total 480 fish are sampled and their nuclear DNA is extracted. They then studied the variability in seven loci using an EPIC (exon-primed, intron-crossing polymerase chain reaction) method and used MCMC methods to find the number of parental populations.
         The results they found were somewhat different from earlier studies on these fish in the same regions. In an earlier study, they had looked at variability in mtDNA. This study using mtDNA found three genetically different groups: 1) a northern group extending from Mauritania to Guinea, 2) a central group distributed from Côte d’Ivoire to Cameroon, and 3) a southern group with populations extending from Gabon to Angola. Also, they found a correlation between geographical distance and genetic differentation (the larger the geographical distance, the more genetic differences).
        The study in this paper found genetic differentiation at finer scale, so within the three groups found in the mtDNA study, they found genetically distinct samples whereas these samples appeared genetically the same using the mtDNA markers. Also, this paper found no correlation between the geographical distance and genetic differentation. Sam suggested that this might be because maybe only the male fish move away from where they are born. If the females of a certain population tend not to migrate then the mtDNA of that population will not mix with that of a different population and so you expect to see more difference in mtDNA as the geographical distances become larger. The nuclear DNA of different populations then does mix because of the migrating males.