Serial Founder Effects During Range Expansion: A Spatial Analog of Genetic Drift
Serial Founder Effects During Range Expansion: A Spatial Analog of Genetic Drift
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DOI：
10.1534/genetics.112.139022
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发表时间：
2012-05-01
期刊：
影响因子：
3.3
通讯作者：
Excoffier, Laurent
中科院分区：
文献类型：
--
作者：
Slatkin, Montgomery;Excoffier, Laurent
范围扩张导致一系列创始人事件。我们表明，在一维栖息地中，这些创始人事件是随机交配群体中遗传漂变的空间模拟。由连续的创始人事件创建的等位基因频率的空间序列相当于有效大小 k(e)（创始人的有效数量）群体中等位基因频率的时间序列。我们在离散人口模型中推导了 k(e) 的表达式，该模型允许当地人口增长和现有人口之间的迁移。如果存在选择，则净效应大约由选择系数与连续创始事件之间的代数的乘积决定。我们使用单个群体的模型来分析计算源群体中存在的等位基因的几个量：（i）它在一系列定植事件中幸存下来的概率，（ii）它在最后一个群体中达到指定阈值频率的概率，以及（iii）每个群体中频率的均值和方差。我们表明，解析理论提供了对模拟结果的良好近似。我们的近似结果是，每个新群体中中性等位基因的平均杂合性降低了 1 - 1/(2k(e)) 倍。因此，即使存在种群间迁移，冲浪的种群遗传后果也可以通过有效创建者数量和有效选择系数来近似预测。我们还表明，我们的分析结果适用于连续分布群体的范围扩展模型。
Range expansions cause a series of founder events. We show that, in a one-dimensional habitat, these founder events are the spatial analog of genetic drift in a randomly mating population. The spatial series of allele frequencies created by successive founder events is equivalent to the time series of allele frequencies in a population of effective size k(e), the effective number of founders. We derive an expression for k(e) in a discrete-population model that allows for local population growth and migration among established populations. If there is selection, the net effect is determined approximately by the product of the selection coefficients and the number of generations between successive founding events. We use the model of a single population to compute analytically several quantities for an allele present in the source population: (i) the probability that it survives the series of colonization events, (ii) the probability that it reaches a specified threshold frequency in the last population, and (iii) the mean and variance of the frequencies in each population. We show that the analytic theory provides a good approximation to simulation results. A consequence of our approximation is that the average heterozygosity of neutral alleles decreases by a factor of 1 - 1/(2k(e)) in each new population. Therefore, the population genetic consequences of surfing can be predicted approximately by the effective number of founders and the effective selection coefficients, even in the presence of migration among populations. We also show that our analytic results are applicable to a model of range expansion in a continuously distributed population.