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Many species worldwide are highly genetically structured and represent historically isolated populations which can be considered as intraspecific units. These units are important as they represent genetically diverse populations of the same species, necessary for sustaining a population. Lack of genetic diversity can have negative effects on the reproductive capabilities of individuals. In the present study, the phylogeography and population structure of 3 species of sharks – Carcharhinus falciformis, Carcharhinus limbatus, Carcharhinus longimanus – and 2 species of rays – Aetobatus narinari and Aetobatus ocellatus was studied. The genetic markers used include Control Region (D-loop), Cytochrome Oxidase subunit I and Cytochrome b of mitochondrial DNA. Phylogenetic trees were built using a Maximum Likelihood approach for each genus, and haplotype networks constructed for each species. Phylogenetic analysis indicates that C. limbatus may be paraphyletic, and that A. narinari and A. ocellatus are allopatric in their distribution, with the former restricted to the Atlantic, and the latter distributed in the Indo-Pacific Ocean basin. The haplotype analysis demonstrated significant population structure among populations inhabiting different ocean basins – Atlantic and Indo-Pacific – with two broad lineages being observed for all of them. However, the within population variation was high for species like Carcharhinus longimanus indicating the need to further expand the study focusing on individual ocean basins. Elasmobranch fishing is an important part of fisheries sector. These species are extremely vulnerable to overfishing and anthropogenic pressures due to their life histories. Therefore, identification of genetically distinct populations would enable designing of effective management and conservation strategies.
Key words: Genetic diversity. Population structure. Sharks. Rays. Mitochondrial DNA.
