Abstract
Despite the global importance of the Nile tilapia Oreochromis niloticus, especially to aquaculture, knowledge of genetic variability within native populations is still limited. While several studies have assessed genetic differentiation across the major drainage basins of Africa, relatively little effort has focused on characterizing genetic differentiation at finer scales. We assessed genetic variation in O. niloticus within and among nine drainage basins in Ghana using nuclear microsatellite DNA markers as the basis for identifying potential units of conservation among wild populations. We screened 312 wild individuals using eight nuclear microsatellite DNA markers. We found moderate genetic diversity within and differentiation among all wild populations studied, with strong signals of recent demographic bottlenecks in several populations. Genetic structure among 11 populations suggested the presence of up to ten management units (MUs). In particular, the Black Volta and the Tano–Asuhyea populations, which were the most genetically distinct and geographically isolated and may be most at risk of loss of genetic diversity over time, may well represent evolutionary significant units. Therefore, at the minimum, the Black Volta and Tano–Asuhyea populations should be prioritized for conservation actions to sustain them over the long-term.
Highlights
Elmira MohandesanThe Nile tilapia (Oreochromis niloticus) is the third most cultured species worldwide, with a 2018 production of 4.5 million metric tons [1]
The genetic diversity observed among wild populations of Nile tilapia in this study was higher than that found in a similar study conducted in Ghana narrowly within the
The objective of this study was to assess genetic variation in O. niloticus within and among drainage basins in Ghana using nuclear microsatellite DNA markers to aid in detecting potential units of conservation within wild populations
Summary
Elmira MohandesanThe Nile tilapia (Oreochromis niloticus) is the third most cultured species worldwide, with a 2018 production of 4.5 million metric tons [1]. Given the importance of O. niloticus to aquaculture and commercial fisheries, in Africa, it is surprising that our knowledge of genetic diversity within and among populations is still rather limited. Most research has focused on characterizing aquaculture performance differences among geographically defined strains [2,3,4], with comparatively little attention to population genetic differentiation in the wild. Several early studies have attempted to cover multiple major drainage basins in Africa where O. niloticus occurs. Allozyme markers showed genetic differentiation among western and eastern African populations [5,6], suggesting the effects of paleogeographic events. Allozyme and mitochondrial restriction fragment length polymorphisms showed genetic differentiation of western African, Ethiopian Rift Valley, and Nile drainage populations [7]
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