Data files for: Hazardous loss of genetic diversity through selective sweeps in asexual populations

With the two-fold cost of sex, derived asexual organisms have an immediate reproductive advantage over their sexual sisters.  Yet the \"twiggy'' phylogenetic distribution of asexual lineages implies that they go extinct relatively quickly over evolutionary time.  Meanwhile, bacteria and archaea have persisted for billions of years without requiring sexual reproduction. A simple explanation for this difference is that prokaryotes have very large population sizes that are not subject to the accumulation of deleterious mutations, but this implies that drift and mutational meltdown dominate derived asexual populations.  

We explored a different hazard, quantifying the degree to which genetic variation is lost in asexual populations experiencing selective sweeps.  Even though large populations generate diversity by mutation during sweeps, we find that populations that are safe from mutational meltdown may still be reduced to dangerous effective population sizes by sweeps.  Thus, ironically...

由于性的二倍代价（two-fold cost of sex），衍生无性生殖生物相较于有性生殖的同种个体，具备即时生殖优势。然而，无性生殖谱系呈枝梢状的系统发育分布特征，表明它们在进化时间尺度上会相对快速地走向灭绝。与此同时，细菌与古菌无需进行有性生殖，却已存续了数十亿年之久。针对这一差异的一种简单解释是：原核生物（prokaryotes）拥有极为庞大的种群规模，不会受到有害突变（deleterious mutations）的积累影响，但这意味着遗传漂变（genetic drift）与突变崩溃（mutational meltdown）会在衍生的无性生殖种群中占据主导地位。

本研究探讨了另一种潜在风险，对经历选择性清除（selective sweeps）的无性生殖种群中遗传变异的丢失程度进行了量化分析。尽管大型种群在选择性清除过程中可通过突变产生遗传多样性，但我们发现，即便本不会发生突变崩溃的种群，仍可能因选择性清除而被缩减至具有生存风险的有效种群大小（effective population size）。因此，颇具讽刺意味的是……