Center for Computational Medicine and Bioinformatics, University of Michigan, Ann Arbor, Michigan 48109, USA.
Genetics. 2011 Oct;189(2):579-93. doi: 10.1534/genetics.111.129296. Epub 2011 Jul 20.
Simulation studies have demonstrated that a variety of patterns in worldwide genetic variation are compatible with the trends predicted by a serial founder model, in which populations expand outward from an initial source via a process in which new populations contain only subsets of the genetic diversity present in their parental populations. Here, we provide analytical results for key quantities under the serial founder model, deriving distributions of coalescence times for pairs of lineages sampled either from the same population or from different populations. We use these distributions to obtain expectations for coalescence times and for homozygosity and heterozygosity values. A predicted approximate linear decline in expected heterozygosity with increasing distance from the source population reproduces a pattern that has been observed both in human genetic data and in simulations. Our formulas predict that populations close to the source location have lower between-population gene identity than populations far from the source, also mirroring results obtained from data and simulations. We show that different models that produce similar declining patterns in heterozygosity generate quite distinct patterns in coalescence-time distributions and gene identity measures, thereby providing a basis for distinguishing these models. We interpret the theoretical results in relation to their implications for human population genetics.
模拟研究表明，全球遗传变异中的多种模式与串行创始模型所预测的趋势一致，在该模型中，种群通过一个过程从初始来源向外扩张，其中新种群仅包含其亲代种群遗传多样性的子集。在这里，我们为串行创始模型下的关键数量提供了分析结果，推导出了从同一群体或不同群体中采样的两个谱系的合并时间分布。我们使用这些分布来获得合并时间以及纯合度和杂合度值的预期。预计异质性预期随距离源种群的增加而呈近似线性下降，再现了在人类遗传数据和模拟中观察到的模式。我们的公式预测，接近源位置的种群的种群间基因同一性低于远离源的种群，这也反映了从数据和模拟中获得的结果。我们表明，产生相似异质性下降模式的不同模型会产生截然不同的合并时间分布和基因同一性度量模式，从而为区分这些模型提供了基础。我们根据对人类群体遗传学的影响来解释理论结果。
