Abstract
BackgroundGeological evolution of the African continent has been subject to complex processes including uplift, volcanism, desert formation and tectonic rifting. This complex geology has created substantial biogeographical barriers, and coupled with anthropogenic introductions of freshwater fishes, has influenced the genetic diversity, connectivity and sub-structuring of the teleost fauna. Nile perch, Lates niloticus, is an iconic fish in Africa and is of high commercial importance, both in the species’ native range and where it has been translocated. However, the species is in decline and there is a need to understand its population genetic structure to facilitate sustainable management of the fishery and aquaculture development.MethodologyNile perch tissue samples were acquired from two West and four East (Lakes; Albert, Kyoga, Victoria and Turkana) African locations. Nineteen polymorphic microsatellite loci were used to study the genetic variation among populations across regions (West and East Africa), as well as between native and introduced environments within East Africa.Principal findings and their significanceResults revealed strong and significant genetic structuring among populations across the sampled distribution (divergence across regions, FCT = 0.26, P = 0.000). STRUCTURE analysis at a broad scale revealed K = 2 clusters, the West African individuals were assigned to one cluster, while all individuals from the East African region, regardless of whether native or introduced, were assigned to another cluster. The distinct genetic clusters identified in the current study between the West and East African Nile perch, appear to have been maintained by presence of biogeographic barriers and restricted gene flow between the two regions. Therefore, any translocations of Nile perch should be carefully considered across the regions of West and East Africa. Further analysis at a regional scale revealed further structuring of up to K = 3 genetic clusters in East African Nile perch. Significantly (P < 0.05) lower genetic diversity based on analysis of allelic richness (AR) was obtained for the two translocated populations of Lake Kyoga (AR = 3.61) and Lake Victoria (AR = 3.52), compared to Nile perch populations from their putative origins of Lakes Albert (AR = 4.12) and Turkana (AR = 4.43). The lower genetic diversity in the translocated populations may be an indication of previous bottlenecks and may also indicate a difficulty for these populations to persist and adapt to climatic changes and anthropogenic pressures that are currently present in the East African region.
Highlights
Advances in the knowledge-base of African freshwater fisheries have been made over the last five decades [1,2,3]
The strong genetic structure is a function of restricted levels of gene flow between populations across biogeographical barriers, for the Nile perch in East Africa
The results in the current study clearly show that the Nile perch in Lake Victoria is still genetically similar to the Nile perch in Lake Albert, with shallow but significant FST (P = 0.003), these populations have become divergent from Lake Turkana individuals (FST = 0.18, P = 0.003; Table 3, Fig 4) which lies in the eastern side of the East African Rift (EAR) [82]
Summary
Advances in the knowledge-base of African freshwater fisheries have been made over the last five decades [1,2,3]. For African fisheries, these threats include increases in urbanisation linked to human population growth, exotic fish introductions, overfishing, and sedimentation / pollution as a result of changes in land utilisation. The impacts of these threats are noticeable in the freshwater lake basins of East Africa [3,4,5]. Geological evolution of the African continent has been subject to complex processes including uplift, volcanism, desert formation and tectonic rifting This complex geology has created substantial biogeographical barriers, and coupled with anthropogenic introductions of freshwater fishes, has influenced the genetic diversity, connectivity and sub-structuring of the teleost fauna. The species is in decline and there is a need to understand its population genetic structure to facilitate sustainable management of the fishery and aquaculture development
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