Mitochondrial Diversity and Time Divergence of Commonly Cultured Cichlids in Nigeria

Aim: The aims are to study the genetic diversity and population structure of Tilapia fish species in Nigeria using mtDNA D-loop region and time divergence of these various groups of fish to give a baseline information for fish management and conservation programs.

Methodology: Blood samples from four species of tilapia were collected with the use of FTA cards for DNA extraction and PCR amplification. A 941bp long fragment, including the D-loop, was subsequently used for analysis. Molecular diversity indices and Tajima’s selective test were determined. A phylogenetic tree was constructed for all the four fish species using UPGMA. The divergence time among the four fish species using MEGA5 software.

Place and Duration of Study: The study was carried out in the Biotechnology Centre, Federal University of Agriculture, Abeokuta Nigeria between. Genotyping and Optimization of PCR conditions were carried out at STAB VIDA Lda, Madan Parque, Rua dos Inventores, 2825-182 Caparica Portugal. Total duration of study was between February to August 2015.

Results: Sarotherodon melanotheron has the highest nucleotide diversity (π), mean number of pairwise differences and number of polymorphic site, while the least was observed in Sarotherodon galiIaeus. The highest number of monomorphic site and the highest sequences conservation percentage was observed in Sarotherodon galiIaeus.

The Neighbour joining tree revealed six (6) clusters with no clear sub-structuring among the sampled fish populations. The smallest divergence time (about 31 mya) was observed between Sarotherodon galilaeus and Sarotherodon melanotheron. Sarotherodon spp diverged from Oreochromis niloticus about 32.5 mya.

Conclusion: The present study revealed that the sampled Tilapia species from Nigeria represent a single stock. The existing low levels of genetic variability observed here may compromise the evolutionary plasticity of the Tilapia species population. These findings indicate an urgent need for the careful monitoring of the harvesting of Tilapia species in Nigeria.