Schoenle Laura A, Dudek Alana M, Moore Ignacio T, Bonier Frances
Department of Biological Sciences, Virginia Tech, 1405 Perry St., Blacksburg, VA 24061, United States.
Department of Biological Sciences, Virginia Tech, 1405 Perry St., Blacksburg, VA 24061, United States; Biology Department, Queen's University, Biosciences Complex 3523, Kingston, ON, K7L 3N6, Canada.
Horm Behav. 2017 Apr;90:1-7. doi: 10.1016/j.yhbeh.2017.02.002. Epub 2017 Feb 20.
Glucocorticoid hormones facilitate responses to environmental challenges by mediating diverse physiological and behavioral changes, including resource mobilization and altered reproductive effort. Elevated glucocorticoids might indicate that an individual is facing high levels of environmental challenges and thus, elevated concentrations might be associated with reduced fitness (CORT-fitness hypothesis). Alternatively, the energetic demands of reproduction might be a challenge that requires elevated glucocorticoids to mobilize resources to support reproductive effort, ultimately increasing reproductive investment and fitness (CORT-adaptation hypothesis). Investigations of glucocorticoid-fitness relationships have yielded mixed results. Variation in the direction of this relationship could be caused in part by differences in the contexts in which the relationship was assessed. Incorporating context, such as life history stage, could be key to understanding the role of glucocorticoids in influencing fitness outcomes. We investigated the relationship between corticosterone and reproductive effort and success within a single life history stage: incubation of eggs. In an observational study, we measured baseline corticosterone in incubating female red-winged blackbirds (Agelaius phoeniceus), monitored incubation behavior, and determined hatching success for each nest. Incubating birds with higher baseline corticosterone concentrations had more frequent, shorter incubation bouts and spent less time overall incubating their clutches of eggs than birds with lower corticosterone concentrations. Elevated corticosterone was also associated with lower clutch mass, but neither corticosterone nor incubation effort were correlated with hatching success. Although experimental tests are needed to establish causation, these results suggest that during the incubation period, corticosterone might shift resource investment towards self-maintenance, and away from current reproductive effort.
糖皮质激素通过介导多种生理和行为变化，包括资源调动和生殖努力的改变，来促进对环境挑战的反应。糖皮质激素水平升高可能表明个体正面临高水平的环境挑战，因此，浓度升高可能与适应性降低有关（皮质酮-适应性假说）。或者，繁殖的能量需求可能是一个挑战，需要升高的糖皮质激素来调动资源以支持生殖努力，最终增加生殖投资和适应性（皮质酮-适应假说）。对糖皮质激素与适应性关系的研究结果不一。这种关系方向的变化可能部分是由于评估该关系的背景不同所致。纳入诸如生活史阶段等背景因素，可能是理解糖皮质激素在影响适应性结果中作用的关键。我们在单个生活史阶段：孵卵期，研究了皮质酮与生殖努力和成功之间的关系。在一项观察性研究中，我们测量了正在孵卵的雌性红翅黑鹂（Agelaius phoeniceus）的基础皮质酮水平，监测了孵卵行为，并确定了每个巢穴的孵化成功率。与皮质酮浓度较低的鸟类相比，基础皮质酮浓度较高的孵卵鸟类孵卵次数更频繁、每次孵卵时间更短，总体上花费在孵卵上的时间更少。皮质酮水平升高还与窝卵质量较低有关，但皮质酮水平和孵卵努力均与孵化成功率无关。尽管需要进行实验测试来确定因果关系，但这些结果表明，在孵卵期，皮质酮可能会将资源投资从当前的生殖努力转向自我维持。
