Goodnight Charles J
Department of Biological Sciences, University of Illinois at Chicago, P.O. Box 4348, Chicago, IL, 60680.
Evolution. 1988 May;42(3):441-454. doi: 10.1111/j.1558-5646.1988.tb04151.x.
Models of founder events have focused on the reduction in the genetic variation following a founder event. However, recent work (Bryant et al., 1986; Goodnight, 1987) suggests that when there is epistatic genetic variance in a population, the total genetic variance within demes may actually increase following a founder event. Since the additive genetic variance is a statistical property of a population and can change with the level of inbreeding, some of the epistatic genetic variance may be converted to additive genetic variance during a founder event. The model presented here demonstrates that some of the additive-by-additive epistatic genetic variance is converted to additive genetic variance following a founder event. Furthermore, the amount of epistasis converted to additive genetic variance is a function of the recombination rate and the propagule size. For a single founder event of two individuals, as much as 75% of the epistatic variance in the ancestral population may become additive genetic variance following the founder event. For founder events involving two individuals with free recombination, the relative contribution of epistasis to the additive genetic variance following a founder event is equal to its proportion of the total genetic variance prior to the founder event. Traits closely related to fitness are expected to have relatively little additive genetic variance but may have substantial nonadditive genetic variance. Founder events may be important in the evolution of fitness traits, not because they lead to a reduction in the genetic variance, but rather because they lead to an increase in the additive genetic variance.
奠基者事件模型主要关注奠基者事件后遗传变异的减少。然而，最近的研究（布莱恩特等人，1986年；古德奈特，1987年）表明，当种群中存在上位性遗传方差时，奠基者事件后deme内的总遗传方差实际上可能会增加。由于加性遗传方差是种群的一种统计特性，并且会随着近亲繁殖水平的变化而改变，一些上位性遗传方差可能在奠基者事件期间转化为加性遗传方差。这里提出的模型表明，一些加性×加性上位性遗传方差在奠基者事件后会转化为加性遗传方差。此外，转化为加性遗传方差的上位性量是重组率和繁殖体大小的函数。对于由两个个体组成的单个奠基者事件，在奠基者事件后，祖先种群中多达75%的上位性方差可能会变成加性遗传方差。对于涉及两个自由重组个体的奠基者事件，奠基者事件后上位性对加性遗传方差的相对贡献等于其在奠基者事件前总遗传方差中的比例。预计与适合度密切相关的性状具有相对较少的加性遗传方差，但可能具有大量的非加性遗传方差。奠基者事件在适合度性状的进化中可能很重要，不是因为它们导致遗传方差的减少，而是因为它们导致加性遗传方差的增加。
