Lynch Michael, Latta Leigh, Hicks Justin, Giorgianni Matthew
Department of Biology, University of Oregon, Eugene, Oregon, 97403.
Evolution. 1998 Jun;52(3):727-733. doi: 10.1111/j.1558-5646.1998.tb03697.x.
In an effort to provide insight into the role of mutation in the maintenance of genetic variance for life-history traits, we accumulated spontaneous mutations in 10 sets of clonal replicates of Daphnia pulex for approximately 30 generations and compared the variance generated by mutation with the standing level of variation in the wild population. Mutations for quantitative traits appear to arise at a fairly high rate in this species, on the order of at least 0.6 per character per generation, but have relatively small heterozygous effects, changing the phenotype by less than 2.5% of the mean. The mean persistence time of a new mutation affecting life-history/body-size traits is approximately 40 generations in the natural population, which requires an average selection coefficient against new mutations of approximately 3% in the heterozygous state. These data are consistent with the idea that the vast majority of standing genetic variance for life-history characters may be largely a consequence of the recurrent introduction of transient cohorts of mutations that are at least conditionally deleterious and raise issues about the meaning of conventional measures of standing levels of variation for fitness-related traits.
为了深入了解突变在维持生活史性状遗传变异中的作用，我们在大约30代的时间里，在10组大型溞克隆复制品中积累自发突变，并将突变产生的变异与野生种群中现有的变异水平进行比较。在这个物种中，数量性状的突变似乎以相当高的速率出现，每代每个性状至少0.6个，但其杂合效应相对较小，使表型变化小于平均值的2.5%。影响生活史/体型性状的新突变在自然种群中的平均持续时间约为40代，这需要对杂合状态下的新突变有大约3%的平均选择系数。这些数据与以下观点一致：生活史性状的绝大多数现有遗传变异可能在很大程度上是反复引入至少有条件有害的短暂突变群体的结果，这引发了关于适应性相关性状现有变异水平传统测量方法意义的问题。
