Data from: Starvation effects on nitrogen and carbon stable isotopes of animals: an insight from meta-analysis of fasting experiments

Nitrogen and carbon stable isotopic compositions (δ15N and δ13C) of consumers have been used for physiological and food web studies. Previous studies have shown δ15N and δ13C values are affected by several biological and environmental factors during starvation, but the generality of the effect of starvation on δ15N and δ13C values has not yet been tested. Here, we performed a meta-analysis to evaluate the effects of starvation on δ15N and δ13C values of consumers, and the underlying factors that may explain the observed variation. The Δ15N and Δ13C values were calculated as the differences between the final δ15N and δ13C values of consumers (post-starvation) and the pre-starvation values on each experiment. Our meta-analysis showed a large variation in the Δ15N and Δ13C values of consumers [Δ15N range: –0.82 to 4.30‰; mean: 0.47‰) and Δ13C range: –1.92 to 2.62‰; mean: 0.01‰]. The Δ15N values of most consumers increased along the length of the starvation period and were influenced by nitrogen excretion and thermoregulation types, probably because differences in nitrogen metabolism and thermoregulation affect nitrogen processing and excretion rates. None of our predictor variables accounted for the variation in Δ13C values, which showed both increases and decreases due to fasting. Our findings suggest that starvation results in changes in consumer δ15N values which are mainly explained by the length of the fasting period and by nitrogen and energy metabolism, but the underlying mechanisms of the starvation effects on δ13C values seem to be more complex than previously thought.

消费者的氮、碳稳定同位素组成（δ¹⁵N和δ¹³C）已被广泛应用于生理学研究与食物网相关研究。过往研究表明，饥饿状态下，δ¹⁵N和δ¹³C值会受到多种生物与环境因素的影响，但饥饿对δ¹⁵N和δ¹³C值的影响是否具有普遍性，目前尚未得到实证检验。本研究开展了一项元分析（meta-analysis），以评估饥饿对消费者δ¹⁵N和δ¹³C值的影响，并探究可解释观测到的同位素变异的潜在驱动因素。Δ¹⁵N与Δ¹³C值通过计算各实验中消费者饥饿后的最终δ¹⁵N、δ¹³C值与饥饿前初始值的差值得到。本元分析结果显示，消费者的Δ¹⁵N与Δ¹³C值存在显著变异：Δ¹⁵N的取值范围为–0.82‰至4.30‰，均值为0.47‰；Δ¹³C的取值范围为–1.92‰至2.62‰，均值为0.01‰。多数消费者的Δ¹⁵N值随饥饿时长的延长而升高，且受氮排泄方式与体温调节类型的影响，这可能是因为氮代谢与体温调节的差异会改变氮的代谢加工与排泄速率。本研究的所有预测变量均无法解释Δ¹³C值的变异，该值会因禁食行为同时出现升高与降低的情况。本研究结果表明，饥饿会导致消费者的δ¹⁵N值发生改变，该效应主要可通过禁食时长、氮代谢与能量代谢进行解释；但饥饿对δ¹³C值的影响机制，似乎比此前学界的认知更为复杂。