1. There is increasing evidence that populations of non‐target wildlife species can evolve tolerance to pesticides. As ecosystems become increasingly exposed to chemical contaminants globally, it is important to consider not only the immediate consequences of contaminant exposure but also the potential costs associated with evolved responses. Theory predicts there may be trade‐offs, including increased susceptibility to parasites, associated with evolved pesticide tolerance. It remains unclear, however, how environmental context (i.e. presence/absence of pesticides in the contemporary environment) interacts with evolved pesticide tolerance levels to influence infection outcomes.
2. Several studies have demonstrated that wood frog (Rana sylvatica) populations close to agriculture, where frequent exposure to pesticides is more likely, show higher baseline tolerance to pesticides than do populations far from agriculture. Using eight wood frog populations from across an agricultural gradient, we explored patterns of variation in susceptibility to parasites associated with a population's proximity to agriculture (a proxy for pesticide tolerance), and how these patterns are influenced by experimental exposure of tadpoles to the insecticide carbaryl. We did this by first placing tadpoles in an environment containing the pesticide carbaryl (1 mg/L) or in a pesticide‐free control environment for 5 days, and subsequently exposing tadpoles to trematodes (Echinostoma trivolvis) or ranavirus (frog virus 3).
3. We found that variation in trematode susceptibility was related to the tadpole populations’ proximity to agriculture. Individuals from populations located close to agriculture were modestly more susceptible to trematode infections than individuals from populations farther from agriculture. Ranavirus susceptibility was not associated with proximity to agriculture.
4. Surprisingly, exposure to carbaryl increased the survival rates of tadpoles infected with ranavirus. There were no other significant effects of carbaryl exposure on the measured disease outcomes.
5. This study provides evidence for a potential trade‐off between trematode resistance and putative pesticide tolerance. We show that host populations can vary significantly in their susceptibility to pathogens, but that pesticide exposure does not always increase parasite susceptibility or uniformly exacerbate disease outcomes. Further research is needed to determine how genetic variation among populations impact susceptibility to parasites, and if these patterns of susceptibility are consistent across space and time.

中文翻译：

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幼虫蛙的感染水平在种群水平上的变化不受农药暴露的影响

1. 越来越多的证据表明非目标野生动植物种群可以发展对农药的耐受性。随着生态系统在全球范围内日益暴露于化学污染物，重要的是不仅要考虑污染物暴露的直接后果，而且还要考虑与应对措施有关的潜在成本。理论预测，可能存在权衡取舍，包括对杀虫剂的耐受性与对寄生虫的敏感性增加有关。但是，尚不清楚环境背景（即当代环境中是否存在农药）与不断发展的农药耐受性水平如何相互作用以影响感染结果。
2. 几项研究表明，靠近农业的林蛙（林蛙）种群比经常远离农业的种群对农药的基线耐受性更高，在该种群中，农药经常暴露于农药中的可能性更高。利用来自整个农业梯度的八只蛙蛙种群，我们探索了与人口接近农业（代表农药耐受性）相关的寄生虫敏感性变化的模式，以及and对杀虫剂西维因的实验性暴露如何影响这些模式。 。为此，我们先将t放在含有杀虫剂西维因（1毫克/升）的环境中或在无农药的控制环境中放置5天，然后将t暴露于吸虫（棘皮chin虫（Echinostoma trivolvis））或鼻病毒（青蛙病毒3）。
3. 我们发现，吸虫的易感性变化与the种群接近农业有关。来自农业附近人群的个体比来自农业以外人群的个体温和地更容易受到吸虫感染的影响。鼻病毒的易感性与邻近农业无关。
4. 出乎意料的是，暴露于西维因可提高na病毒感染的t的存活率。西维因暴露对测得的疾病结局没有其他显着影响。
5. 这项研究提供了在吸虫抗性和假定的杀虫剂耐受性之间可能折衷的证据。我们表明，寄主种群对病原体的敏感性差异很大，但是接触农药并不总是会增加寄生虫的敏感性或统一加剧疾病的后果。需要进行进一步的研究以确定种群之间的遗传变异如何影响对寄生虫的易感性，以及这些易感性模式在空间和时间上是否一致。