Geographical Distance and Genetic Differentiation of Some Populations of Tilapia guineensis (Bleeker, 1862) in Nigerian Coastal Waters

E.A. Ukenye and I.A. Taiwo

Background and Objective: Assessment of genetic diversity is crucial for breeding, conservation and management programmes, especially in species of Tilapia being important source of animal protein in many developing countries. In this regard, the evaluation of the relationship between geographical and genetic relatedness of Tilapia guineensis populations is important because it allows for ascertaining the role of gene flow and other factors that shape the genetic structure of the fish populations. Materials and Methods: A total of 120 randomly selected fish samples from twelve coastal populations and nine microsatellite loci were considered for the present population genetic study. Results: Microsatellite analysis showed that the genetic distance between T. guineensis populations in River Ethiope and Brass (2 km apart) was 0.30 reflecting low genetic distance. Populations in Oron and Ibaka (1 km apart) and those in Ishaka and Igbokoda (1 km apart) had genetic distances of 0.01, respectively. The highest geographical distance was between fish populations in Oron and Epe (29 km), however, the genetic distance between these populations is low (0.03). Geographical distance seems to have less influence on the genetic relationship among the studied populations. Nevertheless, the populations are highly differentiated as assessed by FST values of 0.12-0.66. Conclusion: This is evidenced by the low gene flow of less than one migrant per generation. Thus, the general notion that geographical proximity enhances genetic similarity but discourages genetic differentiation does not hold in T. guineensis populations found in Nigerian coastal waters.

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