Begun D J, Aquadro C F
Section of Genetics and Development, Cornell University, Ithaca, New York 14853.
Genetics. 1991 Dec;129(4):1147-58. doi: 10.1093/genetics/129.4.1147.
We have estimated DNA sequence variation and differentiation within and between Drosophila melanogaster and its sibling species, Drosophila simulans, using six-cutter restriction site variation at yellow-achaete (y-ac), phosphogluconate dehydrogenase (Pgd), and period (per). These three gene regions are of varying distance from the telomere of the X chromosome and range from very low to moderate rates of recombination in D. melanogaster. According to Tajima's test of neutrality, the Pgd region has been influenced by balancing selection in D. melanogaster. This is consistent with previous data suggesting the allozyme polymorphism at this locus is visible to selection. The Hudson, Kreitman, Aguadé test of neutrality reveals a significant departure from neutrality for the y-ac region compared to the per or rosy regions in D. simulans. There is also a significant departure for the y-ac region compared to the Adh 5' flanking region in D. melanogaster. In both species the departure appears to be due to reduced variation at y-ac compared to that expected from divergence between D. simulans and D. melanogaster. We conclude that recent hitchhiking associated with the selective fixation of one or more advantageous mutants in the y-ac region is the best explanation for reduced variation at y-ac.
我们利用黄身-无刚毛（y-ac）、6-磷酸葡萄糖酸脱氢酶（Pgd）和周期蛋白（per）基因上六碱基切割限制酶切位点的变异，估算了黑腹果蝇及其近缘种拟果蝇内部和之间的DNA序列变异及分化情况。这三个基因区域与X染色体端粒的距离各不相同，在黑腹果蝇中的重组率范围从极低到中等。根据田岛中性检验，Pgd区域在黑腹果蝇中受到平衡选择的影响。这与之前的数据一致，表明该位点的等位酶多态性能够被选择所识别。哈德森、克赖特曼、阿瓜德中性检验显示，与拟果蝇中的per或朱红色区域相比，y-ac区域显著偏离中性。与黑腹果蝇中的乙醇脱氢酶（Adh）5'侧翼区域相比，y-ac区域也有显著偏离。在这两个物种中，这种偏离似乎是由于y-ac区域的变异相较于拟果蝇和黑腹果蝇之间的分化预期有所减少。我们得出结论，最近与y-ac区域中一个或多个有利突变的选择性固定相关的搭便车效应，是y-ac区域变异减少的最佳解释。
