Cheverud James M, Routman Eric J
Department of Anatomy and Neurobiology, Washington University School of Medicine, Saint Louis, Missouri, 63110.
Evolution. 1996 Jun;50(3):1042-1051. doi: 10.1111/j.1558-5646.1996.tb02345.x.
The role of epistasis in evolution and speciation has remained controversial. We use a new parameterization of physiological epistasis to examine the effects of epistasis on levels of additive genetic variance during a population bottleneck. We found that all forms of epistasis increase average additive genetic variance in finite populations derived from initial populations with intermediate allele frequencies. Average additive variance continues to increase over many generations, especially at larger population sizes (N = 32 to 64). Additive-by-additive epistasis is the most potent source of additive genetic variance in this situation, whereas dominance-by-dominance epistasis contributes smaller amounts of additive genetic variance. With additive-by-dominance epistasis, additive genetic variance decreases at a relatively high rate immediately after a population bottleneck, rebounding to higher levels after several generations. Empirical examples of epistasis for murine adult body weight based on measured genotypes are provided illustrating the varying effects of epistasis on additive genetic variance during population bottlenecks.
上位性在进化和物种形成中的作用一直存在争议。我们使用一种新的生理上位性参数化方法来研究上位性对种群瓶颈期间加性遗传方差水平的影响。我们发现，所有形式的上位性都会增加源自具有中等等位基因频率的初始种群的有限种群中的平均加性遗传方差。平均加性方差在许多代中持续增加，尤其是在较大的种群规模（N = 32至64）时。在这种情况下，加性×加性上位性是加性遗传方差的最有效来源，而显性×显性上位性贡献的加性遗传方差量较小。对于加性×显性上位性，种群瓶颈后加性遗传方差立即以相对较高的速率下降，几代后反弹至更高水平。提供了基于测量基因型的小鼠成年体重上位性的实证例子，说明了上位性在种群瓶颈期间对加性遗传方差的不同影响。
