Long J C
Department of Anthropology, University of New Mexico, Albuquerque 87131.
Genetics. 1991 Feb;127(2):417-28. doi: 10.1093/genetics/127.2.417.
A method for simultaneously estimating the admixture proportions of a hybrid population and Wright's fixation index, FST, for that hybrid is presented. It is shown that the variance of admixture estimates can be partitioned into two components: (1) due to sample size, and (2) due to evolutionary variance (i.e., genetic drift). A chi-square test used to detect heterogeneity of admixture estimates from different alleles, or loci, can now be corrected for both sources of random errors. Hence, its value for the detection of natural selection from heterogeneous admixture estimates is improved. The estimation and testing procedures described above are independent of the dynamics of the admixture process. However, when the admixture dynamics can be specified, FST can be predicted from genetic principles. Two admixture models are considered here, gene flow and intermixture. These models are of value because they lead to very different predictions regarding the accumulation of genes from the parental populations and the accumulation of variance due to genetic drift. When there is not evidence for natural selection, and it is appropriate to apply these models to data, the variance effective size (Ne) of the hybrid population can be estimated. Applications are made to three human populations: two of these are Afro-American populations and one is a Yanomamö Indian village. Natural selection could not be detected using the chi-square test in any of these populations. However, estimates of effective population sizes do lead to a richer description of the genetic structure of these populations.
本文提出了一种同时估计杂交群体的混合比例以及该杂交群体的赖特固定指数FST的方法。结果表明，混合比例估计值的方差可分为两个部分：（1）由于样本量导致的方差，以及（2）由于进化方差（即遗传漂变）导致的方差。用于检测来自不同等位基因或位点的混合比例估计值异质性的卡方检验，现在可以针对这两种随机误差来源进行校正。因此，其在从异质混合比例估计值中检测自然选择方面的价值得到了提高。上述估计和检验程序与混合过程的动态无关。然而，当可以确定混合动态时，可以根据遗传原理预测FST。这里考虑了两种混合模型，基因流和混合。这些模型很有价值，因为它们对于来自亲本群体的基因积累以及由于遗传漂变导致的方差积累会得出非常不同的预测。当没有自然选择的证据，并且适用于将这些模型应用于数据时，可以估计杂交群体的方差有效大小（Ne）。本文将该方法应用于三个人类群体：其中两个是非洲裔美国人群体，一个是雅诺马马印第安村庄。在这些群体中，使用卡方检验均未检测到自然选择。然而，有效群体大小的估计确实能更丰富地描述这些群体的遗传结构。
