Data from: Long-term dynamics of adaptation in asexual populations

Experimental studies of evolution have increased greatly in recent years, stimulated by the growing power of genomic tools. However, organismal fitness remains the ultimate metric for interpreting these experiments, and the dynamics of fitness remain poorly understood over long timescales. Here, we examine fitness trajectories for 12 Escherichia coli populations during 50,000 generations. Mean fitness appears to increase without bound, consistent with a power law. We also derive this power-law relation theoretically by incorporating clonal interference and diminishing-returns epistasis into a dynamical model of changes in mean fitness over time.近年来，随着基因组学工具（genomic tools）性能的持续提升，进化实验研究取得了显著进展。然而，生物体适合度（organismal fitness）仍是解读此类实验的终极衡量指标，且长期时间尺度下适合度的动态变化机制仍未得到充分阐释。本研究针对12个大肠杆菌（Escherichia coli）种群在50000代演化过程中的适合度轨迹（fitness trajectories）展开分析。研究结果显示，群体平均适合度呈现无界增长态势，与幂律（power law）规律相符。本研究还通过将克隆干涉（clonal interference）与收益递减上位性（diminishing-returns epistasis）整合至平均适合度随时间变化的动力学模型中，从理论层面推导出了该幂律关系。