Recombination Alters the Dynamics of Adaptation on Standing Variation in Laboratory Yeast Populations
Recombination Alters the Dynamics of Adaptation on Standing Variation in Laboratory Yeast Populations
复制标题
DOI：
10.1093/molbev/msx278
复制
发表时间：
2018-01-01
影响因子：
10.7
通讯作者：
Desai, Michael M.
中科院分区：
文献类型：
--
作者：
Kosheleva, Katya;Desai, Michael M.
有益突变的发生率和选择性效应，以及种群规模和重组率等种群遗传因素，决定了适应的结果以及这一过程在遗传多样性模式中留下的特征。先前对微生物进化的实验研究主要集中在最初的克隆群体上，发现适应的特点是新的经过严格选择的有益突变，这些突变会迅速席卷至固定。在这里，我们研究不同异型杂交酵母种群的进化，跟踪随着时间的推移适应的速率和遗传基础。我们结合了以不同异交率进化的 18 个芽殖酵母群体的适应性和等位基因频率变化的时间序列测量，以推断对常备遗传变异的适应驱动因素。与最初的克隆群体相比，我们发现适应是由大量弱选择的连锁变体驱动的。经历不同异型杂交率的种群以不同的方式利用这种选定的变异：无性种群通过快速、低效且高度可变的克隆固定而进化，而有性种群则通过逐渐打破选定变异之间的连锁不平衡来不断适应。我们的结果证明了重组如何通过诱导从基因型选择到个体等位基因选择的转变来维持长时间的适应，并显示普遍的连锁选择如何影响进化动力学。
The rates and selective effects of beneficial mutations, together with population genetic factors such as population size and recombination rate, determine the outcomes of adaptation and the signatures this process leaves in patterns of genetic diversity. Previous experimental studies of microbial evolution have focused primarily on initially clonal populations, finding that adaptation is characterized by new strongly selected beneficial mutations that sweep rapidly to fixation. Here, we study evolution in diverse outcrossed yeast populations, tracking the rate and genetic basis of adaptation over time. We combine time-serial measurements of fitness and allele frequency changes in 18 populations of budding yeast evolved at different outcrossing rates to infer the drivers of adaptation on standing genetic variation. In contrast to initially clonal populations, we find that adaptation is driven by a large number of weakly selected, linked variants. Populations undergoing different rates of outcrossing make use of this selected variation differently: whereas asexual populations evolve via rapid, inefficient, and highly variable fixation of clones, sexual populations adapt continuously by gradually breaking down linkage disequilibrium between selected variants. Our results demonstrate how recombination can sustain adaptation over long timescales by inducing a transition from selection on genotypes to selection on individual alleles, and show how pervasive linked selection can affect evolutionary dynamics.