Rouzine I M, Coffin J M
Department of Microbiology and Molecular Biology, Tufts University, 136 Harrison Avenue, Boston, MA 02111, USA.
Theor Popul Biol. 2007 Mar;71(2):239-50. doi: 10.1016/j.tpb.2006.09.002. Epub 2006 Sep 28.
Earlier, using the semi-deterministic solitary wave approach, we have investigated accumulation of pre-existing beneficial alleles in genomes consisting of a large number of simultaneously evolving sites in the presence of selection and infrequent recombination with small rate r per genome. Our previous results for the dynamics of the fitness distribution of genomes are now interpreted in terms of the life cycle of recombinant clones. We show that, at sufficiently small r, the clones dominating fitness classes, at the moment of their birth, are nearly the best fit in a population. New progeny clones are mostly generated by parental genomes whose fitness falls within a narrow interval in the middle of the high-fitness tail of fitness distribution. We also derive the fitness distribution for the distant ancestors of sites of a randomly sampled genome and show that its form is controlled by a single composite model parameter proportional to r. The ancestral fitness distribution differs dramatically from the fitness distribution of the entire ancient population: it is much broader and localized in the high-fitness tail of the ancient population. We generalize these results to the case of moderately small r to conclude that, regardless of fitness of an individual, all its distant ancestors are exceptionally well fit.
此前，我们使用半确定性孤立波方法，研究了在选择作用以及每基因组重组率(r)较低且重组不频繁的情况下，由大量同时进化位点组成的基因组中预先存在的有益等位基因的积累情况。我们之前关于基因组适应度分布动态的结果，现在根据重组克隆的生命周期来解释。我们表明，在(r)足够小的情况下，在出生时主导适应度等级的克隆，在种群中几乎是最适应的。新的子代克隆大多由其适应度落在适应度分布高适应度尾部中间狭窄区间内的亲本基因组产生。我们还推导了随机抽样基因组位点的远祖的适应度分布，并表明其形式由一个与(r)成比例的单一复合模型参数控制。祖先适应度分布与整个古代种群的适应度分布有显著差异：它更宽，且集中在古代种群的高适应度尾部。我们将这些结果推广到(r)适中较小的情况，得出结论：无论个体的适应度如何，其所有远祖都极其适应。
