Mueller Laurence D, Joshi Amitabh, Santos Marta, Rose Michael R
Department of Ecology and Evolutionary Biology, University of California, Irvine, CA 92697, USA.
J Genet. 2013 Dec;92(3):349-61. doi: 10.1007/s12041-013-0296-1.
Census population size, sex-ratio and female reproductive success were monitored in 10 laboratory populations of Drosophila melanogaster selected for different ages of reproduction. With this demographic information, we estimated eigenvalue, variance and probability of allele loss effective population sizes. We conclude that estimates of effective size based on genefrequency change at a few loci are biased downwards. We analysed the relative roles of selection and genetic drift in maintaining genetic variation in laboratory populations of Drosophila. We suggest that rare, favourable genetic variants in our laboratory populations have a high chance of being lost if their fitness effect is weak, e.g. 1% or less. However, if the fitness effect of this variation is 10% or greater, these rare variants are likely to increase to high frequency. The demographic information developed in this study suggests that some of our laboratory populations harbour more genetic variation than expected. One explanation for this finding is that part of the genetic variation in these outbred laboratory Drosophila populations may be maintained by some form of balancing selection. We suggest that, unlike bacteria, medium-term adaptation of laboratory populations of fruit flies is not primarily driven by new mutations, but rather by changes in the frequency of preexisting alleles.
我们对10个因繁殖年龄不同而选择的黑腹果蝇实验室种群的普查种群大小、性别比和雌性繁殖成功率进行了监测。利用这些人口统计学信息，我们估计了特征值、方差以及等位基因丢失有效种群大小的概率。我们得出结论，基于少数位点基因频率变化的有效大小估计值存在向下偏差。我们分析了选择和遗传漂变在维持果蝇实验室种群遗传变异中的相对作用。我们认为，在我们的实验室种群中，罕见的有利遗传变异如果其适应性效应较弱，例如1%或更低，就很有可能丢失。然而，如果这种变异的适应性效应为10%或更高，这些罕见变异很可能会增加到高频。本研究中得出的人口统计学信息表明，我们的一些实验室种群所拥有的遗传变异比预期的要多。这一发现的一种解释是，这些远交实验室果蝇种群中的部分遗传变异可能通过某种形式的平衡选择得以维持。我们认为，与细菌不同，果蝇实验室种群的中期适应性并非主要由新突变驱动，而是由现有等位基因频率的变化驱动。
