International Research Fellowship Program: Fitness Cost and Neuroendocrine Correlates of Premature Breeding

该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。国际研究奖学金项目使美国科学家和工程师能够在国外进行9至24个月的研究。该计划的奖励为联合研究提供了机会，并利用独特或互补的设施、专业知识和国外的实验条件。该奖项将支持Timothy J. greaves博士与德国马克斯普朗克鸟类研究所的Michaela Hau博士以及美国加州大学戴维斯分校的Tom Hahn博士进行为期24个月的研究。几乎所有动物，包括鸟类，都有繁殖活动的季节性周期。这些循环代表了在有利的环境条件下确保后代生产的适应性。在温带地区，光周期（即日长）提供了一个“无噪声”的环境。在某一天，每年都没有变化的季节性线索。因此，大多数物种依靠光周期来决定一年中的时间。甚至在生活在相对稳定的栖息地（如热带）的物种中，繁殖的季节性变化也得到了证明，这表明选择倾向于跨纬度的繁殖活动的季节性调节。然而，形成脊椎动物性腺周期的选择压力的本质仍然未知。这在一定程度上是由于方法上的限制，限制了在野外通过实验修改性腺激活时间的能力。这项研究验证了一个假设，即精确的繁殖时间是对与不合时宜的繁殖事件相关的适应性成本的反应。通过在自由生活的大山雀身上安装微型发光二极管（LED）来操纵感知到的光周期，性腺激活的时间被提前了。头部，在正常性腺发育开始前提供光周期刺激。此外，不合时宜的繁殖对新型神经肽（如kisspeptin，促性腺激素抑制激素）的影响正在研究中；这将使我们更好地了解它们在调节脊椎动物繁殖方面的具体作用。在实验1中，记录了繁殖对的行为、繁殖成功率和存活率。在实验2中，神经内分泌对早熟光周期刺激的反应将使用最先进的技术进行研究。提出的实验是第一个在自由生活的脊椎动物中使用光周期操纵来推进性腺发育，以量化结果对适应性的影响。了解对不合时宜的季节过程起作用的选择压力将有助于解决为什么大多数鸟类和世界范围内大量脊椎动物在性腺大小上表现出明显的周期。他们也将提供一个独特的机会来阐明各种环境线索在大脑中整合的机制。由此产生的知识将有助于理解形成种群和物种应对全球气候变化或向新栖息地扩散的能力的潜在过程（无论是最终的还是近似的）。

0852986GreivesThis award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).The International Research Fellowship Program enables U.S. scientists and engineers to conduct nine to twenty-four months of research abroad. The program's awards provide opportunities for joint research, and the use of unique or complementary facilities, expertise and experimental conditions abroad.This award will support a twenty-four-month research fellowship by Dr. Timothy J. Greives to work with Dr. Michaela Hau at Max Planck Institute for Ornithology in Germany and with Dr. Tom Hahn at the University of California, Davis in the US.Seasonal cycles in reproductive activity are observed in virtually all animals, including birds. These cycles represent adaptations that ensure offspring production during favorable environmental conditions. In the temperate-zone, photoperiod (i.e., day-length) provides a ?noise-free? seasonal cue that does not vary from year to year for a given day. Hence, most species rely on photoperiod to determine the time of year. Seasonal changes in reproduction have even been demonstrated in species living in relatively stable habitats (i.e., the tropics), suggesting that selection favors a seasonal regulation of reproductive activity across latitudes. However, the nature of the selection pressures that shape gonadal cycles in vertebrates remains unknown. This has been due, in part, to methodological constraints limiting the ability to modify experimentally the timing of gonad activation in the field. This fellowship tests the hypothesis that the precise timing of reproduction has evolved in response to fitness costs associated with mistimed breeding events. The timing of gonadal activation is being advanced in free-living great tits through manipulation of perceived photoperiod using a miniature light emitting diode (LED) attached to the birds? head, providing photoperiodic stimulation prior to the start of normal gonadal development. Further, the effect of mistimed reproduction on novel neuropeptides (e.g., kisspeptin, gonadotropin-inhibitory hormone) is being examined; this will enable a better understanding of their specific roles in regulating vertebrate reproduction. In Experiment 1, behavior, reproductive success and survival rates are being documented in breeding pairs. In Experiment 2, neuroendocrine responses to precocious photoperiodic stimulation will be investigated using state-of-the-art techniques. The proposed experiments are the first to advance gonadal development using photoperiod manipulation in a free-living vertebrate to quantify resulting effects on fitness. Understanding the selection pressures that act on mistimed seasonal processes will help to resolve the question of why most avian species, and a large number of vertebrates world-wide, exhibit pronounced cycles in gonad size. They will also provide a unique opportunity to elucidate mechanisms by which diverse environmental cues are integrated within the brain. The knowledge generated will be useful in understanding the underlying processes (both ultimate and proximate) shaping the ability of populations and species to respond to global climate change or spread to new habitats.