Collaborative Research: Interactive Effects of Stress and Nutrition on Reproduction in Birds

合作研究：压力和营养对鸟类繁殖的交互影响斯蒂芬·J·舍赫和里德·鲍曼孟菲斯大学和阿奇博尔德生物站正确的时机繁殖对于动物最大限度地适应是至关重要的。为了在有利于它们生存的条件下繁衍后代，大多数生物依赖于各种环境线索。PIs使用了观察和实验研究相结合的方法来证明食物的数量和质量影响繁殖的时机。佛罗里达灌木鸟(Aphelooma Ululescens)生活在郊区栖息地，可以随意获取人类提供的食物，因此在附近阿奇博尔德生物站(ABS)的野外栖息地繁殖的时间总是比栖息地早。在野外，补充脂肪和蛋白质含量不同的饲料证实了这些营养物质协同作用，促进了繁殖。饲喂高脂肪/高蛋白(HFHP)日粮的雏鸡比对照组和添加高脂肪/低蛋白日粮的雏鸡早睡，增加了母鸡对蛋的分配，并提高了后代的存活率。此外，PI发现，与对照组相比，补充HFHP的成虫越冬存活率有明显增加的趋势(尽管鸟类只是从1-3月才补充)。重要的是，郊区和HFHP野生松鸦的皮质酮(CORT)水平也低于荒地对照。由于皮质醇可以对生殖轴产生负面影响，皮质醇和营养之间的联系暗示了生殖启动的独特机制。PI开发了一个新的模型，展示了资源如何影响压力(CORT)，而压力反过来又影响繁殖的时机。与其他模型不同的是，该模型预测了提前的繁殖时间和减少的年间差异--这与经验观察一致。在繁殖季节非常早的时候，鸟类可能会因为食物供应的减少而受到压力。尽管它们可能会受到其他信号的“生殖启动”，比如光周期，但高水平的皮质醇会抑制生殖。但随着食物变得更可预测或质量更好，压力水平就会降低，抑制作用就会释放，繁殖就会发生。现场和圈养研究将被用来检验与资源质量和/或可预测性相关的压力是环境线索转化为生殖决策的生理机制这一假设。郊区和补充了HFHP的Jay将被植入CORT，以确定它是否会延迟获得随意食物的雌性Jay的生殖。为了了解去除CORT是否会导致生殖轴的提前激活和提前产蛋，在ABS的未添加CORT的雏鸡中，CORT将被阻断。PIs还将通过检查饮食、压力和繁殖时间对卵大小、后代发育以及短期和长期存活的交互影响来评估资源可获得性的最终影响。通过对蓝鸟的圈养研究，PI将进一步研究饮食、压力和生殖之间的相互作用。这些研究允许对食物处理的内分泌反应进行连续采样。PI将比较在提供食物的可预测性上不同的松鸦的生殖激素和应激激素。此外，郊区夜间的光照可能对生殖轴有刺激作用。这一点将通过比较在每日周期的黑暗阶段暴露于低水平光照的鸟儿和没有暴露在黑暗阶段的鸟类的一系列生理参数来进行测试。在自由生活的物种中，压力、环境资源和繁殖之间的相互作用还没有得到彻底的研究，这可能是鸟类繁殖时间的关键。郊区部分强调了与全球城市化模式相关的快速环境变化如何影响自然选择的系统，并说明了潜在的后果。佛罗里达灌木鸟是一个衰落的物种，可能成为许多分类群中越来越多的其他物种的重要模式，这些物种正在或将面临类似的挑战，因为面对越来越多的人类使用，栖息地的持续丧失。这个项目将在多个层面上带来好处。首先，佛罗里达灌木鸦是濒危物种，这项研究可能会提供减缓数量下降的方法。其次，收集到的技术和信息可能被用来缓解其他物种的衰退。第三，压力对生物体的许多方面都有深刻的负面影响(包括人类！)健康，这项研究(和相关项目)将考虑压力、营养、生殖、免疫功能和生存之间的联系：所有这些都具有重要的跨物种影响。

Collaborative Research: Interactive Effects of Stress and Nutrition on Reproduction in BirdsStephan J. Schoech & Reed BowmanUniversity of Memphis & Archbold Biological StationCorrectly timing breeding is essential for animals to maximize their fitness. To produce young when conditions favor their survival, most organisms rely on a variety of environmental cues. The PIs have used a combination of observational and experimental studies to demonstrate that food quantity and quality influence timing of breeding. Florida Scrub-Jays (Aphelocoma coerulescens) in suburban habitats with access to ad libitum human-provided food always breed earlier than jays in wildland habitat at nearby Archbold Biological Station (ABS). In wildlands, supplementation with diets that differ in fat and protein content confirm that these nutrients act in synergy to advance breeding. Birds given high fat/high protein (HFHP) diets lay earlier than controls and jays supplemented with high fat/low protein diet, increase maternal allocation to eggs, and increase survival of offspring. Additionally, the PIs found a strong trend for increased over-winter survival of HFHP-supplemented adults relative to controls (even though birds are only supplemented from Jan-Mar). Importantly, both suburban and HFHP wildland jays also had lower levels of corticosterone (CORT), the avian stress hormone, than wildland controls. Because CORT can negatively affect the reproductive axis, the link between CORT and nutrition suggests a unique mechanism underlying the initiation of reproduction. The PIs have developed a novel model demonstrating how resources influence stress (CORT), which in turn influences timing of breeding. Unlike other models, this predicts both advanced timing of breeding and reduced between-year variation - consistent with empirical observations. Very early in the breeding season, birds may be stressed by reduced food availability. Although they may be "reproductively primed" by other cues, such as photoperiod, high levels of CORT inhibit reproduction. But as food become more predictable or of better quality, stress levels are reduced, releasing the inhibition, allowing breeding to occur. Field and captive studies will be used to test the hypothesis that stress associated with resource quality and/or predictability is the physiological mechanism by which environmental cues are translated into reproductive decisions. Suburban and HFHP-supplemented jays will be implanted with CORT to determine if it delays reproduction in females with access to ad libitum food. To learn whether the removal of CORT results in earlier activation of the reproductive axis and advanced laying, CORT will be blocked in unsupplemented jays at ABS. The PIs also will evaluate the ultimate effects of resource availability by examining the interactive effects of diet, stress, and time of breeding on egg size, offspring development, and short- and long-term survival. Using captive studies on Blue Jays, the PIs will examine further the interactions between diet and stress and reproduction. These studies allow serial sampling of endocrine responses to food treatments. The PIs will compare reproductive and stress hormones in jays that differ in the predictability in which food is provided. In addition, nocturnal light exposure in the suburbs may be stimulatory to the reproductive axis. This will be tested by comparing a suite of physiological parameters in jays that are exposed to low levels of light during the dark phase of the daily cycle with birds that are not. The interactions between stress, environmental resources, and reproduction have not been thoroughly investigated in free-living species and may be critical in how birds time reproduction. The suburban component underscores how rapid environmental change associated with global patterns of urbanization can influence naturally-selected systems, and illustrates the potential consequences. Florida Scrub-Jays are a declining species and may serve as an important model for an increasing number of other species from many taxa that are or will face similar challenges due to continued loss of habitat in the face of increasing human usage.This project will have benefits at multiple levels. First, Florida Scrub-Jays are a threatened species and this research may provide ways in which the decline in numbers may be slowed. Second, techniques and information gleaned may be used to ameliorate declines in other species. Third, stress has profound negative impacts upon many aspects of an organism's (humans included!) health, and this research (and associated projects) will consider links between stress, nutrition, reproduction, immune function, and survivorship: all of which have important cross-species implications.