RESULTS: We found a lower fitness in both irradiated treatments compared to the control ones, but fitness increased over time in the 50.0 mGy.h- 1, suggesting a local adaptation of the populations. Then, the survival rate of C. elegans to S. marcescens was lower for common garden populations that had previously evolved under both irradiation treatments, indicating that evolution in gamma-irradiated environment had a cost on host defense of C. elegans. Furthermore, we showed a trade-off between standardized fitness at the end of the multigenerational experiment and survival of C. elegans to S. marcescens in the control treatment, but a positive correlation between the two traits for the two irradiated treatments. These results indicate that among irradiated populations, those most sensitive to ionizing radiation are also the most susceptible to the pathogen. On the other hand, other irradiated populations appear to have evolved cross-resistance to both stress factors.
CONCLUSIONS: Our study shows that adaptation to an environmental stressor can be associated with an evolutionary cost when a new stressor appears, even several generations after the end of the first stressor. Among irradiated populations, we observed an evolution of resistance to ionizing radiation, which also appeared to provide an advantage against the pathogen. On the other hand, some of the irradiated populations seemed to accumulate sensitivities to stressors. This work provides a new argument to show the importance of considering evolutionary changes in ecotoxicology and for ecological risk assessment.
结果:我们发现与对照相比,两种辐照处理的适应度较低,但随着时间的推移,健身增加了50.0mGy。h-1,表明种群的局部适应。然后,对于以前在两种辐照处理下进化的普通花园种群,秀丽隐杆线虫对S.marcescens的存活率较低,表明在伽玛辐照环境中的演化对秀丽隐杆线虫的宿主防御有一定的代价。此外,我们显示了在多代实验结束时的标准化适应度与秀丽隐杆线虫在对照治疗中的存活率之间的权衡,但两种辐照处理的两种性状之间呈正相关。这些结果表明,在受辐照的人群中,那些对电离辐射最敏感的人也最容易感染病原体。另一方面,其他受辐照的人群似乎对两种应激因素都产生了交叉抗性。
结论:我们的研究表明,当出现新的压力源时,对环境压力源的适应可能与进化成本有关,甚至在第一个压力源结束后的几代人。在受辐照的人群中,我们观察到电离辐射抗性的演变,这似乎也提供了对抗病原体的优势。另一方面,一些受辐照的人群似乎积累了对应激源的敏感性。这项工作提供了一个新的论点,表明在生态毒理学和生态风险评估中考虑进化变化的重要性。