Jimeno Blanca, Prichard Mackenzie R, Landry Devin, Wolf Cole, Larkin Beau, Cheviron Zachary, Breuner Creagh
Division of Biological Sciences, University of Montana, Missoula, MT 59812, USA.
Department of Psychology, Emory University, Atlanta, GA 30322, USA.
Integr Org Biol. 2020 Oct 14;2(1):obaa030. doi: 10.1093/iob/obaa030. eCollection 2020.
Organisms continuously face environmental fluctuations, and allocation of metabolic investment to meet changing energetic demands is fundamental to survival and reproductive success. Glucocorticoid (GC) hormones (e.g., corticosterone [CORT]) play an important role in energy acquisition and allocation in the face of environmental challenges, partly through mediation of energy metabolism. Although GCs and metabolic rate are expected to covary, surprisingly few empirical studies have demonstrated such relationships, especially in wild animals. Moreover, studies testing for associations between GCs and fitness generally do not account for among-individual differences in energy expenditure or energy allocation. We measured CORT (baseline and stress-induced) and metabolic traits (resting metabolic rate [RMR], cold-induced VO [M], and aerobic scope [the difference between M and RMR]) in female tree swallows () during chick-rearing, and tested for their associations with several variables of reproductive performance. We found a positive relationship between RMR and baseline CORT, but no consistent associations between stress-induced CORT (SI-CORT) and M. This suggests that while baseline CORT may be a good indicator of an individual's baseline metabolic investment, SI-CORT responses are not associated with aerobic scope or the upper limits of aerobic performance. Furthermore, we found that metabolic traits were associated with reproductive performance: females with higher reproductive output showed higher M, and also tended to show higher RMR. Overall, these results suggest that metabolic traits are better predictors of reproductive output in tree swallows than CORT concentrations. They further point to the maximal aerobic capacity being higher in females investing more heavily in a current reproductive event, but whether this association reflects trade-offs between current and future reproductive efforts remains to be tested.
生物体不断面临环境波动，分配代谢投入以满足不断变化的能量需求是生存和繁殖成功的基础。糖皮质激素（GC）激素（如皮质酮[CORT]）在面对环境挑战时，部分通过能量代谢的调节，在能量获取和分配中发挥重要作用。尽管预计糖皮质激素和代谢率会协同变化，但令人惊讶的是，很少有实证研究证明这种关系，尤其是在野生动物中。此外，测试糖皮质激素与适应性之间关联的研究通常没有考虑个体在能量消耗或能量分配方面的差异。我们在雌性树燕育雏期间测量了CORT（基线和应激诱导）和代谢特征（静息代谢率[RMR]、冷诱导VO[M]以及有氧代谢范围[M与RMR之间的差异]），并测试了它们与几个繁殖性能变量之间的关联。我们发现RMR与基线CORT之间存在正相关，但应激诱导的CORT（SI - CORT）与M之间没有一致的关联。这表明，虽然基线CORT可能是个体基线代谢投入的良好指标，但SI - CORT反应与有氧代谢范围或有氧性能上限无关。此外，我们发现代谢特征与繁殖性能相关：繁殖产出较高的雌性表现出较高的M，并且也倾向于表现出较高的RMR。总体而言，这些结果表明，代谢特征比CORT浓度更能预测树燕的繁殖产出。它们进一步指出，在当前繁殖事件中投入更多的雌性最大有氧能力更高，但这种关联是否反映了当前和未来繁殖努力之间的权衡仍有待测试。
