van Delden Wilke, Kamping Albert
Department of Genetics, University of Groningen, Kerklaan 30, 9751 NN Haren, THE NETHERLANDS.
Evolution. 1989 Jul;43(4):775-793. doi: 10.1111/j.1558-5646.1989.tb05176.x.
Substantial allele-frequency changes were observed at the Adh and αGpdh loci in a seminatural population of Drosophila melanogaster kept in a tropical greenhouse during 1972-1985. Further analysis of the changes at the Adh and αGpdh loci showed that linkage disequilibrium between these loci occurred for a prolonged period due to the presence of In(2L)t, a long inversion on the left arm of the second chromosome. We observed increases in the frequencies of In(2L)t and of short inversions on the left arm of the second chromosome in subpopulations kept at 29.5°C or 33°C. These inversion-frequency increases were accompanied by an increase in Adh and a decrease in αGpdh frequency. In populations kept at 20°C and 25°C, inversion frequencies decreased, while αGpdh allele frequencies decreased at 25°C and increased at 20°C. At 33°C, egg-to-adult survival of individuals possessing In(2L)t, either in the homokaryotypic or the heterokaryotypic state, was higher than that of the other karyotypes of identical allozyme constitution (i.e., Adh αGpdh ). Thus it seems that In(2L)t has a selective advantage at high temperature. We argue that the observed changes in allele frequencies at the Adh and αGpdh loci are, in part, due to genic selection and are not merely the result of selection acting on the chromosome rearrangements and hitchhiking of the allozymes. The results are discussed with respect to the latitudinal clines found for In(2L)t, Adh, and αGpdh.
1972年至1985年期间，在一个热带温室中饲养的黑腹果蝇半自然种群中，观察到乙醇脱氢酶（Adh）和α-甘油磷酸脱氢酶（αGpdh）位点存在显著的等位基因频率变化。对Adh和αGpdh位点变化的进一步分析表明，由于存在In(2L)t（第二条染色体左臂上的一个长倒位），这些位点之间的连锁不平衡持续了很长一段时间。我们观察到，在保持在29.5°C或33°C的亚种群中，In(2L)t以及第二条染色体左臂上短倒位的频率增加。这些倒位频率的增加伴随着Adh频率的增加和αGpdh频率的降低。在保持在20°C和25°C的种群中，倒位频率降低，而αGpdh等位基因频率在25°C时降低，在20°C时增加。在33°C时，具有In(2L)t的个体，无论是同核型还是异核型，从卵到成虫的存活率都高于具有相同等位酶组成（即Adh αGpdh）的其他核型个体。因此，似乎In(2L)t在高温下具有选择优势。我们认为，在Adh和αGpdh位点观察到的等位基因频率变化部分是由于基因选择，而不仅仅是选择作用于染色体重排和等位酶搭便车的结果。结合In(2L)t、Adh和αGpdh的纬度渐变对结果进行了讨论。
