Dissertation Research: Testosterone-Mediated Life History Tradeoffs in a Lek-Mating Bird: An Integrated Approach using Path Analysis and Experimental Implants

类固醇激素可能是许多鸟类雄性交配成功率差异的近似解释。高水平的睾丸激素可能会提高交配成功率，但随后会降低个体雄性科普病原体的能力，这反过来可能会降低长期存活率。在一个不寻常的交配系统中，雄性会组成群体，在传统的展示场所（或“leks”）向来访的雌性求爱。在列克交配的鸟类中，雄性通常会保卫那些不含雌性资源的领土，只有有限的雄性成功交配，而雌性则会照顾所有的后代。将测量大草原鸡（Tympanuchus cupido）野生种群中天然和实验睾酮水平的影响，这是草原松鸡的lek交配物种。研究设计将使用三种方法来确定睾酮水平与雄性行为、交配成功率和生存率之间的联系。首先，路径分析，一种统计方法，将用于区分自然高水平的睾酮对交配成功的直接益处和通过睾酮增强的性状（梳子大小，行为和领土属性）的间接益处。其次，睾酮的实验操作将验证睾酮，男性属性和交配成功之间的因果关系。最后，通过检查年回报率来测试自然高和实验性增加的睾酮水平的成本。这笔资金将用于支持睾丸激素植入和行为观察的实地工作，以及粪便样本的实验室分析以测量睾丸激素水平。这项研究的智力价值来自于这样一个事实，即这是第一次在lek交配鸟类中进行睾丸激素的实验操作。本研究结合了强大的统计方法与睾酮的实验操作，以阐明激素，激素介导的性状和生殖性能之间的因果关系。自然高或实验性增加睾酮水平的成本将通过对男性生存的影响进行检查。睾丸激素的生理作用是非常有趣的，因为它可以解释众所周知的生活史权衡当前和未来的生殖。需要从单个雄性中采集多个睾酮样本，粪便样本是一种非侵入性方法，可以减少对鸟类的不必要压力，但仍然可以测量睾酮的个体和季节变化。密集的焦点观察将有助于更好地了解lek交配鸟类的行为生态学。这项工作的更广泛的影响包括一个经济上重要的保护鸟类的人口数据。更大的草原鸡种群正在下降的范围内，这项研究将有助于管理行动提供基线生存和繁殖力数据，从健康的人口在堪萨斯。将为一名女研究生和两名女本科生提供研究培训。该项目将促进堪萨斯州立大学和哥伦比亚的密苏里州大学之间的研究合作。结果将通过在Konza Prairie生物站的导游图尔斯和外展计划与公众分享。

Steroid hormones could be a proximate explanation for variation in male mating success in many species of birds. High levels of testosterone may enhance mating success but then reduce the ability of individual males to cope with pathogens which may, in turn, decrease long-term survival. In one unusual mating system, males form groups and court visiting females at traditional display sites (or 'leks'). In lek-mating birds, males typically defend territories that contain no resources for females, only a limited subset of males mate successfully, and females care for all offspring. The effects of natural and experimental testosterone levels in a wild population of greater prairie-chickens (Tympanuchus cupido), a lek-mating species of prairie grouse will be measured. The study design will use three approaches to determine the links among testosterone levels and the behavior, mating success and survival of males. First, path analysis, a statistical method, will be used to distinguish between direct benefits of naturally high levels of testosterone on mating success and indirect benefits through testosterone-enhanced traits (comb size, behavior, and territory attributes). Second, experimental manipulations of testosterone will verify causal relationships among testosterone, male attributes, and mating success. Last, the costs of naturally high and experimentally increased testosterone levels will be tested by examination of yearly return rates. This funding will support field work on testosterone implants and behavioral observations, and laboratory analyses of fecal samples to measure testosterone levels.The intellectual merit of this study accrues from the fact that this is one of the first experimental manipulations of testosterone in a lek-mating bird. This study combines robust statistical methods with experimental manipulations of testosterone to elucidate causal relationships among hormones, hormone-mediated traits, and reproductive performance. The costs of naturally high or experimentally increased testosterone levels will be examined by impacts on male survival. The physiological role of testosterone is of great interest because it could explain well known life history trade-offs between current and future reproduction. Multiple testosterone samples are needed from individual males, and fecal samples are a noninvasive approach that reduces unnecessary stress to the birds but still allows measurement of individual and seasonal variation in testosterone. Intensive focal observations will contribute to a better understanding of the behavioral ecology of lek-mating birds. The broader impacts of this work include demographic data on an economically important game bird of conservation concern. Greater prairie-chicken populations are declining range-wide, and this study will aid management actions by providing baseline survival and fecundity data from healthy populations in Kansas. Research training will be provided for one female graduate student and two undergraduates. This project will foster research collaboration between Kansas State University and the University of Missouri at Columbia. Results will be shared with the public through guided tours and outreach programs at Konza Prairie Biological Station.