Cox M
Arizona Research Laboratories - Biotechnology, 1041 East Lowell Street, Biological Sciences West, Room 246B, University of Arizona, Tucson, AZ 85721, USA.
Ann Hum Genet. 2007 May;71(Pt 3):390-406. doi: 10.1111/j.1469-1809.2006.00327.x. Epub 2006 Nov 28.
Small populations are dominated by unique patterns of variance, largely characterized by rapid drift of allele frequencies. Although the variance components of genetic datasets have long been recognized, most population genetic studies still treat all sampling locations equally despite differences in sampling and effective population sizes. Because excluding the effects of variance can lead to significant biases in historical reconstruction, variance components should be incorporated explicitly into population genetic analyses. The possible magnitude of variance effects in small populations is illustrated here via a case study of Y-chromosome haplogroup diversity in the Vanuatu Archipelago. Deme-based modelling is used to simulate allele frequencies through time, and conservative confidence bounds are placed on the accumulation of stochastic variance effects, including diachronic genetic drift and contemporary sampling error. When the information content of the dataset has been ascertained, demographic models with parameters falling outside the confidence bounds of the variance components can then be accepted with some statistical confidence. Here I emphasize how aspects of the demographic history of a population can be disentangled from stochastic variance effects, and I illustrate the extreme roles of genetic drift and sampling error for many small human population datasets.
小群体主要由独特的方差模式主导，其很大程度上的特征是等位基因频率的快速漂移。尽管遗传数据集的方差成分早已为人所知，但大多数群体遗传学研究仍然平等对待所有采样地点，尽管采样和有效群体大小存在差异。由于排除方差效应会在历史重建中导致显著偏差，因此方差成分应明确纳入群体遗传学分析。本文通过对瓦努阿图群岛Y染色体单倍群多样性的案例研究，说明了小群体中方差效应的可能大小。基于deme的建模用于模拟随时间变化的等位基因频率，并对随机方差效应的积累设置保守的置信区间，包括历时性遗传漂变和当代采样误差。当确定了数据集的信息内容后，参数落在方差成分置信区间之外的人口统计模型就可以在一定的统计置信度下被接受。在这里，我强调了如何将一个群体的人口统计历史的各个方面与随机方差效应区分开来，并且我说明了遗传漂变和采样误差对许多小型人类群体数据集的极端作用。
