Department of Zoology, University of Alberta, Edmonton, Alberta, Canada T6G 2E9.
Genetics. 1987 Sep;117(1):149-53. doi: 10.1093/genetics/117.1.149.
Unbiased estimates of theta = 4Nmicro in a random mating population can be based on either the number of alleles or the average number of nucleotide differences in a sample. However, if there is population structure and the sample is drawn from a single subpopulation, these two estimates of theta behave differently. The expected number of alleles in a sample is an increasing function of the migration rates, whereas the expected average number of nucleotide differences is shown to be independent of the migration rates and equal to 4N(T)micro for a general model of population structure which includes both the island model and the circular stepping-stone model. This contrast in the behavior of these two estimates of theta is used as the basis of a test for population subdivision. Using a Monte-Carlo simulation developed so that independent samples from a single subpopulation could be obtained quickly, this test is shown to be a useful method to determine if there is population subdivision.
在随机交配群体中，无偏估计θ=4Nmicro 可以基于等位基因的数量或样本中核苷酸差异的平均值。然而，如果存在群体结构，并且样本取自单个亚群，则这两种θ的估计值表现不同。样本中的预期等位基因数量是迁移率的递增函数，而预期核苷酸差异的平均值与迁移率无关，对于包括岛屿模型和圆形踏脚石模型在内的一般群体结构模型，其值等于 4N(T)micro。这两种θ估计值的行为差异被用作群体划分检验的基础。使用开发的蒙特卡罗模拟，以便可以快速获得来自单个亚群的独立样本，该检验被证明是一种有用的方法来确定是否存在群体划分。
