Data from: Fitness decline in spontaneous mutation accumulation lines of Caenorhabditis elegans with varying effective population sizes

The rate and fitness effects of new mutations have been investigated by mutation accumulation (MA) experiments in which organisms are maintained at a constant minimal population size to facilitate the accumulation of mutations with minimal efficacy of selection. We evolved 35 MA lines of Caenorhabditis elegans in parallel for 409 generations at three population sizes (N = 1, 10, and 100), representing the first spontaneous long-term MA experiment at varying population sizes with corresponding differences in the efficacy of selection. Productivity and survivorship in the N = 1 lines declined by 44% and 12%, respectively. The average effects of deleterious mutations in N = 1 lines are estimated to be 16.4% for productivity and 11.8% for survivorship. Larger populations (N = 10 and 100) did not suffer a significant decline in fitness traits despite a lengthy and sustained regime of consecutive bottlenecks exceeding 400 generations. Together, these results suggest that fitness decline in very small populations is dominated by mutations with large deleterious effects. It is possible that the MA lines at larger population sizes contain a load of cryptic deleterious mutations of small to moderate effects that would be revealed in more challenging environments.新突变的发生速率及其适合度效应，可通过突变积累（Mutation Accumulation, MA）实验开展研究：此类实验将生物体维持在恒定的最小种群规模下，以在选择作用效能最低的条件下促进突变积累。本研究以秀丽隐杆线虫（Caenorhabditis elegans）为对象，并行构建35个MA品系，在三种种群规模（N=1、10、100）下连续传代409次；这是首个在不同种群规模（对应选择效能存在差异）下开展的自发性长期突变积累实验。种群规模为N=1的品系，其繁殖力与存活率分别下降了44%与12%；经估算，N=1品系中有害突变对繁殖力的平均效应为16.4%，对存活率的平均效应为11.8%。尽管种群规模为N=10与100的群体经历了持续400余代的连续种群瓶颈，但其适合度相关性状并未出现显著下降。综合上述结果可知，极小种群的适合度下降主要由具有强有害效应的突变所主导。种群规模更大的MA品系，可能携带了一批效应大小为中等到轻微的隐匿有害突变，此类突变在更具挑战性的环境中才会显现其效应。