Evolution of adaptation requires predictability and recurrence of functional contexts. Yet organisms live in multifaceted environments that are dynamic and ever changing, making it difficult to understand how complex adaptations evolve. This problem is particularly apparent in the evolution of adaptive maternal effects, which are often assumed to require reliable and discrete cues that predict conditions in the offspring environment. One resolution to this problem is if adaptive maternal effects evolve through preexisting, generalized maternal pathways that respond to many cues and also influence offspring development. Here, we assess whether an adaptive maternal effect in western bluebirds is influenced by maternal stress pathways across multiple challenging environments. Combining 18 years of hormone sampling across diverse environmental contexts with an experimental manipulation of the competitive environment, we show that multiple environmental factors influenced maternal corticosterone levels, which, in turn, influenced a maternal effect on aggression of sons in adulthood. Together, these results support the idea that multiple stressors can induce a known maternal effect in this system. More generally, they suggest that activation of general pathways, such as the hypothalamic-pituitary-adrenal axis, may simplify and facilitate the evolution of adaptive maternal effects by integrating variable environmental conditions into preexisting maternal physiological systems.

中文翻译：

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多个环境压力源可导致适应性母体效应。

适应的发展需要功能上下文的可预测性和重复性。然而，生物体生活在动态且不断变化的多面环境中，这使得很难理解复杂的适应机制如何进化。在适应性产妇效应的演变中，这个问题尤其明显，通常认为这需要预测子代环境状况的可靠且离散的线索。这个问题的一个解决方案是，适应性母体效应是否通过对多种线索做出反应并影响子代发育的既有的，广义的母体途径进化而来。在这里，我们评估在多个具有挑战性的环境中，母体应激途径是否会影响西方蓝鸟的适应性母体效应。结合18年不同环境情况下的激素采样与竞争性环境的实验性操作，我们发现多种环境因素影响孕产皮质激素水平，进而影响孕产妇对成年儿子侵略性的影响。总之，这些结果支持以下观点：多个压力源可以在该系统中诱发已知的母体效应。他们更普遍地认为，通过将可变的环境条件整合到已有的母体生理系统中，激活诸如下丘脑-垂体-肾上腺轴等一般通路可以简化和促进适应性母体效应的演变。我们表明，多种环境因素影响母亲的皮质酮水平，进而影响母亲对成年儿子侵略性的影响。总之，这些结果支持以下观点：多个压力源可以在该系统中诱发已知的母体效应。他们更普遍地认为，通过将可变的环境条件整合到已有的母体生理系统中，激活诸如下丘脑-垂体-肾上腺轴等一般通路可以简化和促进适应性母体效应的演变。我们表明，多种环境因素影响母亲的皮质酮水平，进而影响母亲对成年儿子侵略性的影响。总之，这些结果支持以下观点：多个压力源可以在该系统中诱发已知的母体效应。他们更普遍地认为，通过将可变的环境条件整合到已有的母体生理系统中，激活诸如下丘脑-垂体-肾上腺轴等一般通路可以简化和促进适应性母体效应的演变。