The social environment (i.e., the suite of social interactions that occur among individuals that can result in variation in social ranks) is a commonly overlooked aspect of biology when scientists evaluate the effects of chemical contaminants. The social environment, however, represents the arena in which individual-level performance shapes group- or population-level outcomes and may therefore mediate many of the ultimate consequences of chemicals for wildlife. Here, we evaluated the role that the social environment plays in determining the consequences of pollutant exposure. We exposed groups of juvenile brown trout (Salmo trutta) to an emerging pharmaceutical pollutant that is commonly detected in freshwaters (the benzodiazepine, oxazepam) and allowed them to form dominance hierarchies. Exposure affected dominant and subordinate fish differently, causing fish to become less aggressive at high doses and subordinate fish to become more competitively successful at low doses. These perturbations had further consequences for growth, fin damage, and survival. Exposure also modulated physiological stress in the hierarchy, and social status itself affected how much oxazepam was absorbed in tissues, potentially creating a dynamic feedback loop that further influences the asymmetric effects of exposure on differing social statuses. Many effects followed a “U-shaped” dose-response curve, highlighting the importance of nonlinear, low-dose effects. Altogether, we show that social structure in animal groups can interact with and modulate the effects of an environmental contaminant. We underscore the need to account for an organism’s natural ecological context, including their social environment, in future experiments and environmental risk assessments to predict the effects of chemical contaminants on wildlife.

中文翻译：

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社会地位调节动物群体中化学污染物的行为和生理后果

当科学家评估化学污染物的影响时，社会环境（即个体之间发生的可能导致社会等级变化的一系列社会互动）是生物学中经常被忽视的一个方面。然而，社会环境代表了个人层面的表现影响群体或群体层面结果的舞台，因此可能调解化学品对野生动物的许多最终后果。在这里，我们评估了社会环境在确定污染物暴露后果方面所起的作用。我们暴露了成群的幼年褐鳟 ( Salmo trutta) 到一种在淡水中常见的新兴药物污染物（苯二氮卓类药物、奥沙西泮），并允许它们形成优势等级。暴露对优势鱼和从属鱼的影响不同，导致鱼在高剂量下变得不那么具有攻击性，而从属鱼在低剂量下变得更有竞争力。这些扰动对生长、鳍损伤和生存产生了进一步的影响。暴露还调节了层次结构中的生理压力，社会地位本身会影响组织中奥沙西泮的吸收量，可能会产生一个动态反馈回路，进一步影响暴露对不同社会地位的不对称影响。许多效应遵循“U 形”剂量反应曲线，突出了非线性、低剂量效应的重要性。共，我们表明，动物群体的社会结构可以与环境污染物相互作用并调节其影响。我们强调需要在未来的实验和环境风险评估中考虑生物体的自然生态环境，包括其社会环境，以预测化学污染物对野生动物的影响。