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，但随后会降低雄性个体应对病原体的能力，从而降低长期存活率。在一种不同寻常的交配系统中，雄性形成群体，在传统的展示场所（或“leks”）向来访的雌性求爱。在同父异母交配的鸟类中，雄性通常会保卫没有雌性资源的领地，只有一小部分雄性成功交配，而雌性会照顾所有的后代。大草原鸡（Tympanuchus cupido）是草原松鸡的一种杂交品种，将对野生大草原鸡（Tympanuchus cupido）的自然和实验睾酮水平的影响进行测量。研究设计将使用三种方法来确定睾丸激素水平与男性行为、交配成功和生存之间的联系。首先，路径分析，一种统计方法，将用于区分自然高水平的睾丸激素对交配成功的直接好处和通过睾丸激素增强的特征（梳子大小，行为和领土属性）的间接好处。其次，对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，将通过检查年回报率来检验自然较高和实验性增加的睾丸激素水平的成本。这笔资金将支持睾酮植入和行为观察的实地工作，以及对粪便样本进行实验室分析以测量睾酮水平。这项研究的智力价值来自于这样一个事实，即这是第一次对雄性雄性激素进行实验操作。本研究结合稳健的统计方法和实验操作的睾酮来阐明激素、激素介导的性状和生殖性能之间的因果关系。睾丸激素水平自然升高或通过实验增加的代价将通过对男性生存的影响来检验。睾酮的生理作用引起了极大的兴趣，因为它可以解释众所周知的生活史上当前和未来繁殖之间的权衡。需要从雄性个体中提取多个睾丸激素样本，而粪便样本是一种非侵入性的方法，可以减少对鸟类不必要的压力，但仍然可以测量睾丸激素的个体和季节性变化。密集的焦点观察将有助于更好地理解雄性交配鸟类的行为生态学。这项工作的广泛影响包括对一种具有重要经济价值的野生鸟类的人口统计数据。大草原鸡的数量正在下降，这项研究将通过提供堪萨斯州健康种群的基线生存和繁殖力数据来帮助管理行动。将为一名女研究生和两名本科生提供研究培训。该项目将促进堪萨斯州立大学和密苏里大学哥伦比亚分校之间的研究合作。结果将通过导游和康扎草原生物站的外展项目与公众分享。

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.