Department of Biology, Hamilton College, Clinton, NY, United States.
Department of Natural Resources and Environmental Sciences, University of Nevada, Reno, NV, United States.
Front Immunol. 2018 Jan 31;9:105. doi: 10.3389/fimmu.2018.00105. eCollection 2018.
Life-history theory is fundamental to understanding how animals allocate resources among survival, development, and reproduction, and among traits within these categories. Immediate trade-offs occur within a short span of time and, therefore, are more easily detected. Trade-offs, however, can also manifest across stages of the life cycle, a phenomenon known as carryover effects. We investigated trade-offs on both time scales in two populations of Dall sheep () in Southcentral Alaska. Specifically, we (i) tested for glucocorticoid-mediated carryover effects from the breeding season on reproductive success and immune defenses during parturition and (ii) tested for trade-offs between immune defenses and reproduction within a season. We observed no relationship between cortisol during mating and pregnancy success; however, we found marginal support for a negative relationship between maternal cortisol and neonate birth weights. Low birth weights, resulting from high maternal cortisol, may result in low survival or low fecundity for the neonate later in life, which could result in overall population decline. We observed a negative relationship between pregnancy and bacterial killing ability, although we observed no relationship between pregnancy and haptoglobin. Study site affected bactericidal capacity and the inflammatory response, indicating the influence of external factors on immune responses, although we could not test hypotheses about the cause of those differences. This study helps advance our understanding of the plasticity and complexity of the immune system and provides insights into the how individual differences in physiology may mediate differences in fitness.
生活史理论是理解动物如何在生存、发育和繁殖之间，以及在这些类别中的特征之间分配资源的基础。短期的即时权衡会发生，因此更容易被检测到。然而，权衡也可以跨越生命周期的各个阶段，这种现象被称为延续效应。我们在阿拉斯加中南部的两个多尔绵羊种群中研究了这两个时间尺度上的权衡。具体来说，我们（i）测试了繁殖季节的糖皮质激素介导的延续效应是否会影响分娩期间的繁殖成功和免疫防御，以及（ii）测试了一个季节内免疫防御和繁殖之间的权衡。我们没有发现交配期间皮质醇与怀孕成功率之间存在关系；然而，我们发现母体皮质醇与新生儿出生体重之间存在负相关的微弱支持。由于母体皮质醇水平高而导致的低出生体重可能导致新生儿在以后的生活中生存能力或繁殖力降低，这可能导致整个种群的下降。我们观察到怀孕与杀菌能力之间存在负相关，尽管我们没有发现怀孕与触珠蛋白之间存在关系。研究地点影响了杀菌能力和炎症反应，表明外部因素对免疫反应的影响，尽管我们无法测试这些差异的原因假设。这项研究有助于我们更好地理解免疫系统的可塑性和复杂性，并深入了解个体生理差异如何介导适应度的差异。
