DISSERTATION RESEARCH: Reproductive Senescence in the Florida Scrub-Jay (Aphelocoma coerulescens)

老年鸟类的繁殖性能下降，尽管经验增加可能会带来好处，但通常被归因于衰老。衰老是结构和功能随着时间的推移而逐渐恶化，在脊椎动物中表现为与年龄相关的死亡率增加、生殖力下降或两者兼而有之。衰老的生理学是复杂的，涉及到与年龄相关的体细胞和生殖细胞和组织功能的变化，以及随后这些系统之间相互作用的变化。对我们研究种群的17年数据的分析表明，繁殖者的年龄与所产雏鸟的数量呈二次曲线关系，最年轻和最年长的鸟类繁殖成功率最低。佛罗里达灌木鸦是一种合作繁殖的雀形目鸟类，仅限于佛罗里达半岛残留的灌木橡树栖息地。在这个项目中，研究人员将评估该物种衰老的生殖方面；考虑到生殖内分泌学、应激生理学、卵子孵化率、精子形态、生活史权衡以及与年龄相关的父母行为差异。具体地说，研究人员将进行实验，通过记录随着个体年龄增长而发生的生理变化(主要是内分泌指标)，确定生殖轴(下丘脑-垂体-性腺轴：HPG)的哪个组成部分出现衰老。这个项目的结果将结合观察性和操纵性实验，最终将有助于深入了解鸟类生殖衰老的基础(或结果)的机制。该项目的更广泛影响将主要通过研究生的继续教育来实现。调查人员将在适当的国内和国际场合(例如，在会议和受人尊敬的期刊上)介绍和发表调查结果。同样，这两位研究人员都定期向非专业组织提交研究结果，如鸟类学和自然俱乐部。

A decrease in reproductive performance in older birds, despite the likely benefits of increased experience, is often attributed to senescence. Senescence is the progressive deterioration of structure and function over time, and in vertebrates is manifested as an age-related increase in mortality, decrease in fecundity, or both. The physiology of senescence is complex, and involves age-related changes in function of somatic and reproductive cells and tissues, and subsequent changes in interactions among these systems. Analyses of seventeen years of data from our study population of Florida Scrub-Jays (Aphelocoma coerulescens) reveals a quadratic relationship between breeder age and number of fledglings produced, with the youngest and oldest birds having the lowest reproductive success. The Florida Scrub-Jay is a cooperatively breeding passerine that is restricted to remnant scrub oak habitat of peninsular Florida. In this project, the investigators will assess reproductive aspects of senescence in this species; taking into consideration reproductive endocrinology, stress physiology, egg hatchability, sperm morphology, life history trade-offs, and age-related variance in parental behavior. Specifically, the investigators will conduct experiments to determine which component of the reproductive (hypothalamic-pituitary-gonadal: HPG) axis exhibits senescence by recording physiological changes (primarily endocrine measures) as individuals age. The results from this project which will combine observational and manipulative experiments will ultimately contribute valuable insight into the mechanisms that underlie (or are a result of) avian reproductive senescence. The broader impacts of the project will primarily be realized through the continuing education of a graduate student. The investigators will present and publish findings in appropriate national and international venues (e. g., at meetings and in respected journals). Similarly, both investigators regularly present research findings to lay organizations, such as ornithological and nature clubs.