Molecular genetic diversity and differentiation of Nile tilapia (Oreochromis niloticus, L. 1758) in East African natural and stocked populations
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Date
2020
Journal Title
Journal ISSN
Volume Title
Publisher
BMC Evolutionary Biology
Abstract
The need for enhancing the productivity of fisheries in Africa triggered the introduction of non-native
fish, causing dramatic changes to local species. In East Africa, the extensive translocation of Nile tilapia (Oreochromis
niloticus) is one of the major factors in this respect. Using 40 microsatellite loci with SSR-GBS techniques, we
amplified a total of 664 individuals to investigate the genetic structure of O. niloticus from East Africa in comparison
to Ethiopian and Burkina Faso populations.
Results: All three African regions were characterized by independent gene-pools, however, the Ethiopian
population from Lake Tana was genetically more divergent (Fst = 2.1) than expected suggesting that it might be a
different sub-species. In East Africa, the genetic structure was congruent with both geographical location and
anthropogenic activities (Isolation By Distance for East Africa, R2 = 0.67 and Uganda, R2 = 0.24). O. niloticus from Lake
Turkana (Kenya) was isolated, while in Uganda, despite populations being rather similar to each other, two main
natural catchments were able to be defined. We show that these two groups contributed to the gene-pool of
different non-native populations. Moreover, admixture and possible hybridization with other tilapiine species may
have contributed to the genetic divergence found in some populations such as Lake Victoria. We detected other
factors that might be affecting Nile tilapia genetic variation. For example, most of the populations have gone
through a reduction in genetic diversity, which can be a consequence of bottleneck (G-W, < 0.5) caused by
overfishing, genetic erosion due to fragmentation or founder effect resulting from stocking activities.
Conclusions: The anthropogenic activities particularly in the East African O. niloticus translocations, promoted
artificial admixture among Nile Tilapia populations. Translocations may also have triggered hybridization with the
native congenerics, which needs to be further studied. These events may contribute to outbreeding depression and
hence compromising the sustainability of the species in the region.
Description
Keywords
Cichlids, Fish translocations, Genetic structure, Gene flow, Bottleneck
Citation
Tibihika, P. D., Curto, M., Alemayehu, E., Waidbacher, H., Masembe, C., Akoll, P., & Meimberg, H. (2020). Molecular genetic diversity and differentiation of Nile tilapia (Oreochromis niloticus, L. 1758) in East African natural and stocked populations. BMC Evolutionary Biology, 20(1), 1-20. https://doi.org/10.1186/s12862-020-1583-0