ON THE EFFECT OF FOUNDER EVENTS ON EPISTATIC GENETIC VARIANCE
ON THE EFFECT OF FOUNDER EVENTS ON EPISTATIC GENETIC VARIANCE
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DOI：
10.1111/j.1558-5646.1987.tb05772.x
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发表时间：
1987-01-01
期刊：
影响因子：
3.3
通讯作者：
GOODNIGHT, CJ
中科院分区：
文献类型：
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作者：
GOODNIGHT, CJ
Mayr(1963)提出，由于遗传变异的丧失，来自大量泛栖种群的小的孤立繁殖体偶尔会经历一次基因革命。最近，Templeton(1980a)提出，创始人事件在具有强烈上位性的系统中可能要重要得多。由于这些作者和其他作者的工作，研究创始人事件后总体上位性方差的分布成为一个有趣的理论问题。在这里给出的模型中，共同祖先的度量(Cockerham，1967,1984；Cockerham and Weir，1973；Weir and Cockerham，1973,1977；Tchida and Cockerham，Unpubl.)用于检验已发现的事件对逐个加性上位性的影响。使用这种方法，个体内和种群内的共同祖先或类内相关性，以及祖先种群中的遗传方差分量被用来获得创始人事件之后的种群内和种群间的方差。以单创始人事件为例进行了分析，相对于祖先群体中的加性方差，加性方差对Demes内方差的贡献总是小于1的。然而，相对于祖先群体中的上位性方差，上位性方差对Demes内的方差的贡献总是大于1的。因此，虽然创始人事件减少了加性方差对德米斯内部方差的贡献，但它增加了上位性方差对德米斯内部方差的贡献。上位性方差对个体间方差的贡献与加性方差对个体间方差的贡献没有本质上的区别。这些结果表明，在单一创始人事件之后，上位性方差比加性方差更不可能引起遗传革命。当人们经历多个创始人事件时，情况会发生很大变化。上位性方差最多可以贡献原始值的四倍，而加性方差最大可以贡献原始值的两倍。因此，在单个创始人事件之后相对不重要的上位性，如果允许漂移持续几代人，可能会有重大的进化影响。
Mayr (1963) proposed that small isolated propagules from a large panmictic population would occasionally undergo a genetic revolution due to loss of genetic variability. More recently Templeton (1980a) has suggested that founder events may be much more important in systems that have strong epistasis. Because of the work of these and other authors it becomes an interesting theoretical problem to study the distribution of epistatic variance in a population following a founder event. In the model presented here measures of coancestry (Cockerham, 1967, 1984; Cockerham and Weir, 1973; Weir and Cockerham, 1973, 1977; Tachida and Cockerham, unpubl.) are used to examine the effect of found events on additive-by-additive epistasis. Using this approach, The coancestries, or intraclass correlations, within indivuals and within demes, together with the genetic variance components in the ancestral population are used to obtain thevariance within and among demesfollowing a founder event. Examples are analyzed for single founder event, the contribution of the additive variance to the variance within demes relative to the additive variance in the ancestral population is always less than one. However, the contribution of epistatic variance to the variance within demes relative to the epistatic variance in the ancestral populationis always greater than one. Thus, while a founder event decreases the contribution of additive variance to the variance within demes, it increases the contribution of epistatic variance to the variance within demes. The contribution of epistatic variance to the variance among demes following a single founder event is not qualitatively different from the contribution of additive vraiance to the variance among demes. These results indicate that epistatic variance is less likely than additive variance to cause a genetic revolution following a single founder event. When populations undergo multiple founder events the situation changes considerably. Epistatic variance may contribute as much as four times its original value to the variance among demes, while additive variance can contribute maximally twice its original value to the variance among demes. Thus, epistasis, which is relatively unimportant following a single founder event, may have major evolutionary implications if drift is allowed to continue for several generations.