Department of Biology, Kyushu University, Fukuoka 812, Japan.
Genetics. 1984 Nov;108(3):617-32. doi: 10.1093/genetics/108.3.617.
It has been reported in the previous papers of this series that in the eastern United States and Japan there is a north-to-south cline of additive genetic variance of viability and that the amount of the additive genetic variance in the northern population can be explained by mutation-selection balance. To determine whether or not the difference in the genetic variation in northern and southern populations can be explained by the differences in mutation rate and/or effective population size, numerical calculations were made using population genetic parameters. In addition, the average heterozygosities of the northern and southern populations at ten of 19 polymorphic structural loci surveyed were estimated in relation to the cline of additive genetic variance of viability, and the following findings were obtained. (1) The changes in mutation rate and population size cannot simultaneously explain the difference in additive genetic variance and inbreeding decline between the northern and southern populations. Thus, the operation of some kind of balancing selection, most likely diversifying selection, was suggested to explain the observed excess of additive genetic variance. (2) Estimates of the average heterozygosities of the southern population were not significantly different from those of the northern population. Thus, it was strongly suggested that the excess of additive genetic variance in the southern population cannot be caused by structural loci, but by factors outside the structural loci, and that protein polymorphisms are selectively neutral or nearly neutral.
在本系列的先前论文中已有报道，在美东地区和日本存在生存力加性遗传方差的从北向南的渐变，并且北部种群的加性遗传方差的数量可以用突变-选择平衡来解释。为了确定北部和南部种群遗传变异的差异是否可以用突变率和/或有效种群大小的差异来解释，使用群体遗传参数进行了数值计算。此外，还针对生存力加性遗传方差渐变，估算了调查的 19 个多态结构基因座中 10 个基因座的北部和南部种群的平均杂合度，并得出以下发现。（1）突变率和种群大小的变化不能同时解释北部和南部种群加性遗传方差和近交衰退的差异。因此，建议某种平衡选择（最有可能是多样化选择）来解释观察到的加性遗传方差过剩。（2）南部种群的平均杂合度估计值与北部种群没有显著差异。因此，强烈表明南部种群加性遗传方差过剩不是由结构基因座引起的，而是由结构基因座以外的因素引起的，并且蛋白质多态性是选择性中性或近中性的。
