Data from: A physiological signature of 'cost of reproduction' associated with parental care

Costs of reproduction are an integral and long-standing component of life-history theory, but we still know relatively little about the specific physiological mechanisms underlying these trade-offs. We experimentally manipulated work load during parental care in female European starlings (Sturnus vulgaris) using a combination of attachment of radios or wing-clipping and assessed measures of workload, current breeding productivity, future fecundity, and survival (local return rate) in relation to treatment. Females with radios and wing-clipping (Clip/RT) paid a clear cost of reproduction compared with all other treatment groups: they had lower future fecundity and lower return rates despite having lower current breeding productivity. We then measured 13 physiological traits (including measures of aerobic/metabolic capacity, oxidative stress and muscle damage, intermediary metabolism and energy supply, and immune function). Our results show that the cost of reproduction in Clip/RT females was associated with lower oxygen-carrying capacity (lower hematocrit and hemoglobin levels), lower energy reserves (plasma NEFA and triglyceride levels), decreased immune function (lower haptoglobin levels), and elevated levels of oxidative stress (higher dROMs and lower levels of the endogenous antioxidant uric acid). Our study provides evidence that costs of reproduction involve a widespread decline in physiological function across multiple physiological systems consistent with long-standing ideas of cumulative "wear and tear" and allostatic load.

繁殖代价是生活史理论（life-history theory）中不可或缺且长期存续的组成部分，但目前我们对这些权衡背后的具体生理机制仍知之甚少。本研究通过佩戴无线电追踪器与剪翅相结合的方式，对雌性欧椋鸟（Sturnus vulgaris）育雏期间的工作负荷进行实验操控，并基于处理组别评估了工作负荷、当前繁殖生产力、未来繁殖力以及存活率（本地回归率）相关指标。与所有其他处理组相比，佩戴无线电追踪器且剪翅的雌性欧椋鸟（Clip/RT组）表现出了明确的繁殖代价：尽管其当前繁殖生产力更低，但未来繁殖力与本地回归率均显著降低。随后本研究测定了13项生理指标（涵盖有氧/代谢能力、氧化应激与肌肉损伤、中间代谢与能量供给以及免疫功能相关检测内容）。研究结果显示，Clip/RT组雌性欧椋鸟的繁殖代价与以下生理变化相关：携氧能力下降（红细胞比容与血红蛋白水平降低）、能量储备减少（血浆非酯化脂肪酸（NEFA）与甘油三酯水平降低）、免疫功能受损（触珠蛋白水平降低）以及氧化应激水平升高（活性氧代谢物（dROMs）水平升高，内源性抗氧化剂尿酸水平降低）。本研究提供的证据表明，繁殖代价会导致多个生理系统的生理功能广泛衰退，这与长期以来提出的累积“磨损耗损”与稳态负荷（allostatic load）理论相符。