Fitness decline under osmotic stress in Caenorhabditis elegans populations subjected to spontaneous mutation accumulation at varying population sizes

The consequences of mutations for population fitness depends on their individual selection coefficients and the effective population size. An earlier study of Caenorhabditis elegans spontaneous mutation accumulation lines evolved for 409 generations at three population sizes found that Ne = 1 populations declined significantly in fitness whereas the fitness of larger populations (Ne = 5, 50) was indistinguishable from the ancestral control under benign conditions. To test if larger MA populations harbor a load of cryptic deleterious mutations that are obscured under benign laboratory conditions, we measured fitness under osmotic stress via exposure to hypersaline conditions. The fitness of Ne = 1 lines exhibited a further decline under osmotic stress compared to benign conditions. However, the fitness of larger populations remained indistinguishable from that of the ancestral control. The average effects of deleterious mutations in Ne =1 lines were estimated to be 22% for productivity a...

突变对种群适合度的影响，取决于其个体选择系数与有效种群大小（effective population size）。此前一项针对秀丽隐杆线虫（Caenorhabditis elegans）自发突变积累品系的研究，以三种种群规模对其开展了409代的传代演化，结果发现：有效种群大小为1的种群其适合度显著下降，而较大种群（Ne=5、50）在良性实验室条件下的适合度与祖先对照株无显著差异。为验证较大规模的突变积累种群是否携带了在适宜实验室条件下被掩盖的大量隐蔽有害突变，我们通过高盐胁迫处理模拟渗透胁迫环境，对其适合度进行了测定。与良性培养条件相比，Ne=1品系的适合度在渗透胁迫下进一步降低。然而，较大种群的适合度仍与祖先对照株无显著差异。经估算，Ne=1品系中有害突变对生产力的平均效应可达22%，原文后续内容未完整呈现。