快速适应人群的谱系
Genealogies of rapidly adapting populations
摘要：
一个物种的遗传多样性〈动〉<动>是由其最近的进化历史形成的，可以用来推断人口统计事件或选择性扫描。大多数推理方法都是基于自然选择是一种微弱或罕见的进化力量的零假设。然而，许多物种，特别是病原体，在不断的压力下，以适应不断变化的环境。目前缺乏一个统计框架，从这些人口的多样性数据进行推断。为了实现这一目标，我们探讨了在无性种群的持续适应模型的家谱的属性。我们发现，血统追溯到一个小水池的高度适合的祖先，其中几乎同时合并两个以上的血统经常发生。虽然这种多重合并不太可能在中性结合下发生，但它们在适应性种群中创造了独特的遗传足迹。例如，衍生的中性等位基因的位点频谱是非单调的，并且在高频率处具有峰值，而田岛的D随着样本量的增加而变得越来越负。由于多个合并出现在许多模型的快速适应，我们认为，他们应该被视为一个零模型适应人口。
英文摘要：
The genetic diversity of a species is shaped by its recent evolutionary history and can be used to infer demographic events or selective sweeps. Most inference methods are based on the null hypothesis that natural selection is a weak or infrequent evolutionary force. However, many species, particularly pathogens, are under continuous pressure to adapt in response to changing environments. A statistical framework for inference from diversity data of such populations is currently lacking. Toward this goal, we explore the properties of genealogies in a model of continual adaptation in asexual populations. We show that lineages trace back to a small pool of highly fit ancestors, in which almost simultaneous coalescence of more than two lineages frequently occurs. While such multiple mergers are unlikely under the neutral coalescent, they create a unique genetic footprint in adapting populations. The site frequency spectrum of derived neutral alleles, for example, is non-monotonic and has a peak at high frequencies, whereas Tajima's D becomes more and more negative with increasing sample size. Since multiple merger coalescents emerge in many models of rapid adaptation, we argue that they should be considered as a null-model for adapting populations.
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