Non-African populations of Drosophila melanogaster have a unique origin
Non-African populations of Drosophila melanogaster have a unique origin
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DOI：
10.1093/molbev/msh089
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发表时间：
2004-08-01
影响因子：
10.7
通讯作者：
Veuille, M
中科院分区：
文献类型：
--
作者：
Baudry, E;Viginier, B;Veuille, M
果蝇被广泛用作 DNA 变异研究的模型。然而，多态性模式受到了该物种历史的影响，该物种被认为最近从非洲传播到了世界其他地区。我们分析了 11 个人群的 DNA 序列变异，其中包括四个非洲大陆样本和七个非非洲样本（包括马达加斯加）的四个独立 X 连锁位点。所有四个位点的变异模式都遵循所有非洲人群的中性预期，但由于四个位点中的三个位点存在明显的单倍型二态性，因此在所有非非洲人群中都偏离了中性预期。我们还发现所有非非洲人群都表现出相同的主要单倍型，尽管频率不同。对这些观察结果的一个简单的解释是，所有非非洲种群都源自一个单一祖先种群，该种群经历了多态性的大幅减少，可能是通过瓶颈。不太可能的替代方案涉及同时选择所有四个基因座（包括平衡其中三个基因座的选择），或两个不同群体之间的混合。在非洲人口中观察到规模虽小但意义重大的结构，并且有迹象表明欧亚大陆非非洲人口存在分化。由于种群历史可能导致非平衡变异模式，我们的研究证实，在黑腹果蝇基因组中寻找选择足迹必须包括对其历史的充分了解。
Drosophila melanogaster is widely used as a model in DNA variation studies. Patterns of polymorphism have, however, been affected by the history of this species, which is thought to have recently spread out of Africa to the rest of the world. We analyzed DNA sequence variation in 11 populations, including four continental African and seven non-African samples (including Madagascar), at four independent X-linked loci. Variation patterns at all four loci followed neutral expectations in all African populations, but departed from it in all non-African ones due to a marked haplotype dimorphism at three out of four loci. We also found that all non-African populations show the same major haplotypes, though in various frequencies. A parsimonious explanation for these observations is that all non-African populations are derived from a single ancestral population having undergone a substantial reduction of polymorphism, probably through a bottleneck. Less likely alternatives involve either selection at all four loci simultaneously (including balancing selection at three of them), or admixture between two divergent populations. Small but significant structure was observed among African populations, and there were indications of differentiation across Eurasia for non-African ones. Since population history may result in non-equilibrium variation patterns, our study confirms that the search for footprints of selection in the D. melanogaster genome must include a sufficient understanding of its history.