Data from: Abiotic stress does not magnify the deleterious effects of spontaneous mutations

Although the effects of deleterious alleles often are predicted to be greater in stressful environments, there is no theoretical basis for this prediction and the empirical evidence is mixed. Here we characterized the effects of three types of abiotic stress (thermal, oxidative and hyperosmotic) on two sets of nematode (Caenorhabditis elegans) mutation accumulation (MA) lines that differ by threefold in fitness. We compared the survival and egg-to-adult viability between environments (benign and stressful) and between fitness categories (high-fitness MA, low-fitness MA). If the environment and mutation load have synergistic effects on trait means, then the difference between the high and low-fitness MA lines should be larger in stressful environments. Although the stress treatments consistently decreased survival and/or viability, we did not detect significant interactions between fitness categories and environment types. In contrast, we did find consistent evidence for synergistic effects on (micro)environmental variation. The lack of signal in trait means likely reflects the very low starting fitness of some low-fitness MA lines, the potential for cross-stress responses and the context dependence of mutational effects. In addition, the large increases in the environmental variance in the stressful environments may have masked small changes in trait means. These results do not provide evidence for synergism between mutation and stress.

尽管通常预测有害等位基因在胁迫环境中的有害效应会更强，但这一预测并无理论依据，且相关实证证据莫衷一是。本研究针对三种非生物胁迫——热胁迫、氧化胁迫与高渗胁迫，分析其对两组秀丽隐杆线虫（Caenorhabditis elegans）突变积累（MA）品系适合度的影响，这两组品系的基础适合度相差三倍。我们比较了适宜环境与胁迫环境下，以及高适合度MA品系、低适合度MA品系之间的存活率与卵到成虫生活力差异。若环境与突变负荷对性状均值存在协同效应，则高、低适合度MA品系间的差异在胁迫环境中应更为显著。尽管胁迫处理均显著降低了线虫的存活率和/或生活力，但我们未检测到适合度类别与环境类型间存在显著交互作用。与之相反，我们确实发现了胁迫对微环境变异存在协同效应的一致证据。性状均值未体现显著信号的原因，可能在于部分低适合度MA品系初始适合度极低、存在交叉胁迫响应的可能性，以及突变效应的情境依赖性。此外，胁迫环境下环境方差的大幅提升，可能掩盖了性状均值的微小变化。本研究结果并未为突变与胁迫间的协同效应提供支撑证据。