Peng T X, Moya A, Ayala F J
Department of Ecology and Evolutionary Biology, University of California, Irvine 92717.
Genetics. 1991 Jun;128(2):381-91. doi: 10.1093/genetics/128.2.381.
Overdominance is often invoked to account for the extensive polymorphisms found in natural populations of organisms; overcompensation, however, may be equally or more important. Overcompensation occurs when limiting resources are better exploited by a genetically mixed than by a uniform population, and is often causally related to frequency-dependent selection. We have designed experiments to test whether overcompensation occurs in Drosophila melanogaster, using the Sod locus as a marker. Tests are made at each of two densities and two temperatures for cultures with desired genetic compositions. Both temperature and density have statistically significant effects on the per-female productivity of the cultures. More important, there are strong effects due to overcompensation. Cultures that are more polymorphic are also more productive than less polymorphic ones even when the level of individual heterozygosity is the same in all. There is also overdominance for the Sod locus: the heterozygotes are more productive than either homozygote at every temperature and density, and the differences are statistically significant in several cases. These results corroborate previous studies showing that overdominance may contribute to the maintenance of the Sod polymorphisms. Moreover, our results indicate that the significance of overcompensation as a mechanism to account for polymorphism in natural populations deserves further investigation.
超显性常常被用来解释在生物自然种群中发现的广泛多态性；然而，超补偿可能同样重要甚至更重要。当有限资源在基因混合种群中比在同质种群中得到更好利用时，就会发生超补偿，并且它通常与频率依赖选择有因果关系。我们设计了实验，以果蝇的Sod基因座作为标记，来测试超补偿是否在黑腹果蝇中发生。针对具有所需基因组成的培养物，在两种密度和两种温度下分别进行测试。温度和密度对培养物中每只雌蝇的繁殖力都有统计学上的显著影响。更重要的是，超补偿有很强的影响。即使所有个体的杂合度水平相同，多态性更高的培养物也比多态性较低的培养物繁殖力更强。对于Sod基因座也存在超显性：在每个温度和密度下，杂合子都比任何一种纯合子繁殖力更强，并且在几种情况下差异具有统计学意义。这些结果证实了先前的研究，表明超显性可能有助于维持Sod基因座的多态性。此外，我们的结果表明，超补偿作为一种解释自然种群中多态性的机制，其重要性值得进一步研究。
