Ayala F J, Tracey M L
Proc Natl Acad Sci U S A. 1974 Mar;71(3):999-1003. doi: 10.1073/pnas.71.3.999.
We describe allelic variation at 28 loci in six Caribbean populations of four sympatric species of Drosophila. Within any one species the allelic frequencies are very similar from population to population, although there is evidence of local as well as regional genetic differentiation. The genetic distance is greater between populations from different islands than between populations of the same island. When the allelic frequencies are compared between different species, a remarkable pattern appears. In any pair of species nearly half of the loci have essentially identical allelic frequencies, while nearly the other half of the loci have different alleles and in different frequencies. The loci with nearly identical allelic frequencies are different when different pairs of species are compared. The patterns of allelic variation within and between species are inconsistent with the hypothesis that the variation is adaptively neutral. Migration or mutation cannot explain the patterns of genetic variation, either. Balancing natural selection is the main process maintaining protein polymorphisms in natural populations.
我们描述了四种同域分布的果蝇在六个加勒比海种群中28个基因座的等位基因变异情况。在任何一个物种内，尽管存在局部和区域遗传分化的证据，但不同种群间的等位基因频率非常相似。来自不同岛屿的种群之间的遗传距离大于同一岛屿上种群之间的遗传距离。当比较不同物种间的等位基因频率时，会出现一种显著的模式。在任意一对物种中，近一半的基因座具有基本相同的等位基因频率，而近另一半的基因座具有不同的等位基因且频率各异。当比较不同的物种对时，具有近乎相同等位基因频率的基因座是不同的。物种内部和物种之间的等位基因变异模式与变异是适应性中性的假设不一致。迁移或突变也无法解释遗传变异模式。平衡自然选择是维持自然种群中蛋白质多态性的主要过程。
