Centre for Sustainable Tropical Fisheries and Aquaculture, College of Science and Engineering, James Cook University, Townsville, Queensland, Australia.
National Agricultural Research Organization, National Fisheries Resources Research Institute, Aquaculture Research and Development Center Kajjansi, Kampala, Uganda.
PLoS One. 2018 Jul 11;13(7):e0200001. doi: 10.1371/journal.pone.0200001. eCollection 2018.
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. 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.
Nile 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.
Results 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.
非洲大陆的地质演化经历了抬升、火山活动、沙漠形成和构造分裂等复杂过程。这种复杂的地质条件形成了大量的生物地理屏障，再加上人为引入淡水鱼类，影响了硬骨鱼类的遗传多样性、连通性和亚结构。尼罗河鲈鱼（Lates niloticus）是非洲的标志性鱼类，具有很高的商业价值，无论是在其原生分布区还是在被引入的地方。然而，该物种正在减少，因此需要了解其种群遗传结构，以促进渔业的可持续管理和水产养殖的发展。
从非洲西部的两个地点和东部的四个湖泊（阿尔伯特湖、基奥加湖、维多利亚湖和图尔卡纳湖）采集尼罗河鲈鱼的组织样本。使用 19 个多态微卫星标记研究了不同地区（西部和东部非洲）以及东非本土和引入环境之间的种群遗传变异。
研究结果表明，在所采样的分布区域内，不同种群之间存在强烈且显著的遗传结构（区域间的分化，FCT = 0.26，P = 0.000）。在较大尺度上的 STRUCTURE 分析显示，存在 K = 2 个聚类，西部非洲个体被分配到一个聚类中，而来自东非地区的所有个体，无论是否是本土或引入的，都被分配到另一个聚类中。在当前研究中，在西部和东部非洲的尼罗河鲈鱼之间确定的独特遗传聚类，似乎是由生物地理屏障的存在和两个区域之间受限的基因流维持的。因此，在西部和东部非洲地区之间进行任何尼罗河鲈鱼的转移都应该谨慎考虑。在区域尺度上的进一步分析揭示了东非尼罗河鲈鱼存在高达 K = 3 个遗传聚类的进一步结构。基于等位基因丰富度（AR）的分析，基奥加湖（AR = 3.61）和维多利亚湖（AR = 3.52）两个迁移种群的遗传多样性显著降低（P < 0.05），而来自其可能起源的湖泊阿尔伯特（AR = 4.12）和图尔卡纳（AR = 4.43）的尼罗河鲈鱼种群的遗传多样性较高。迁移种群中的较低遗传多样性可能表明存在先前的瓶颈效应，也可能表明这些种群难以维持和适应目前在东非地区存在的气候变化和人为压力。
