Stressors such as antibiotics, herbicides, and pollutants are becoming increasingly common in the environment. The effects of stressors on populations are typically studied in homogeneous, nonspatial settings. However, most populations in nature are spatially distributed over environmentally heterogeneous landscapes with spatially restricted dispersal. Little is known about the effects of stressors in these more realistic settings. Here, we combine laboratory experiments with novel mathematical theory to rigorously investigate how a stressor’s physiological effect and spatial distribution interact with dispersal to influence population dynamics. We prove mathematically that if a stressor increases the death rate and/or simultaneously decreases the population growth rate and yield, a homogeneous distribution of the stressor leads to a lower total population size than if the same amount of the stressor was heterogeneously distributed. We experimentally test this prediction on spatially distributed populations of budding yeast (Saccharomyces cerevisiae). We find that the antibiotic cycloheximide increases the yeast death rate but reduces the growth rate and yield. Consistent with our mathematical predictions, we observe that a homogeneous spatial distribution of cycloheximide minimizes the total equilibrium size of experimental metapopulations, with the magnitude of the effect depending predictably on the dispersal rate and the geographic pattern of antibiotic heterogeneity. Our study has implications for assessing the population risk posed by pollutants, antibiotics, and global change and for the rational design of strategies for employing toxins to control pathogens and pests.

中文翻译：

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应激源对空间分布的种群的承载能力的影响。

压力源，例如抗生素，除草剂和污染物在环境中变得越来越普遍。应激源对种群的影响通常是在同质的非空间环境中进行的。但是，自然界中的大多数种群在空间上分布于环境异质景观上，且空间分布受到限制。在这些更加现实的环境中，对于压力源的影响知之甚少。在这里，我们将实验室实验与新颖的数学理论相结合，以严格研究应激源的生理效应和空间分布如何与分散相互作用，从而影响种群动态。我们用数学方法证明，如果压力增加死亡率和/或同时降低种群增长率和产量，与同等数量的应激源进行异构分布相比，应激源的均匀分布导致总体种群规模较小。我们通过实验对出芽酵母在空间上分布的种群进行了这一预测（酿酒酵母（Saccharomyces cerevisiae）。我们发现抗生素环己酰亚胺增加了酵母的死亡率，但降低了生长速率和产量。与我们的数学预测一致，我们观察到环己酰亚胺的均匀空间分布可最大程度地减少实验性种群的总平衡大小，其影响程度可预测地取决于抗生素异质性的扩散速度和地理模式。我们的研究对评估污染物，抗生素和全球变化带来的人口风险以及合理设计使用毒素控制病原体和害虫的策略具有重要意义。