Department of Integrative Biology, University of California, Berkeley, California, 94720.
Evolution. 2013 Nov;67(11):3274-89. doi: 10.1111/evo.12202. Epub 2013 Aug 27.
We propose a method that uses genetic data to test for the occurrence of a recent range expansion and to infer the location of the origin of the expansion. We introduce a statistic ψ (the directionality index) that detects asymmetries in the 2D allele frequency spectrum of pairs of population. These asymmetries are caused by the series of founder events that happen during an expansion and they arise because low frequency alleles tend to be lost during founder events, thus creating clines in the frequencies of surviving low-frequency alleles. Using simulations, we show that ψ is more powerful for detecting range expansions than both FST and clines in heterozygosity. We also show how we can adapt our approach to more complicated scenarios such as expansions with multiple origins or barriers to migration and we illustrate the utility of ψ by applying it to a data set from modern humans.
我们提出了一种利用遗传数据来检验近期范围扩张并推断扩张起源位置的方法。我们引入了一个统计量 ψ（方向性指数），用于检测群体对中 2D 等位基因频率谱的不对称性。这些不对称性是由扩张过程中一系列创始事件引起的，因为在创始事件中低频等位基因往往会丢失，从而在幸存的低频等位基因频率中产生渐变。通过模拟，我们表明 ψ 在检测范围扩张方面比 FST 和杂合性渐变都更有效。我们还展示了如何将我们的方法应用于更复杂的场景，例如具有多个起源或迁移障碍的扩张，并通过将 ψ 应用于现代人类数据集来说明其效用。
