Testosterone in Female Songbirds: Natural, Sexual, and Correlated Responses to Selection

男性和女性在某些方面相似，在其他方面不同。差异的产生可能是因为一种性别受到更大的生殖竞争（性选择）或因为两性在生态上的差异（自然选择）。由于男性和女性拥有相同的基因组，他们也会受到选择的相关反应，当一种性别的选择偏爱的基因变异（“如父如子”）在另一种性别中被携带（“如父如女”）时，就会发生这种情况。如果对一种性别有利的属性对另一种性别不利，相关反应可能会成为一种进化约束。类固醇激素是导致性别差异的近似机制之一。它们可能在发育早期组织组织，或在生命后期激活特征表达。当荷尔蒙对男性和女性的影响相似时，就有可能对选择产生相关的反应。这一提议的重点是类固醇激素睾酮(T)及其对鸣禽物种黑眼junco成年雄性和雌性性别差异的综合影响。这项研究有四个目标。第一种是通过实验提高雌性体内的睾酮(T)，并测量其对雌性表型（如外表、行为）的影响。其次是确定升高的T在女性中是适应性的还是非适应性的。第三是通过测量暴露于固定剂量的激素兴奋剂（GnRH）后T的变化来评估两性内部和两性之间相关反应的潜力。第四是通过比较T在男性和女性攻击行为激活中的作用来评估性独立性。本提案中描述的研究将为已经令人印象深刻的20年数据库增加新的内容，为培养具有不同背景的未来科学家提供机会，进行控制论，以及实验室和现场实验，解决生物差异的近似和最终解释的整合。这个广泛的数据库将为持续的合成、编译和网络开发提供素材，并将为这位主要研究者的工作、她的合作者和其他将获得这个金矿的人做出重大贡献。这个网络研究项目也将丰富印第安纳大学和其他地方的课程。研究结果的潜在社会意义包括：(1)环境中激素活性物质的影响；(2)对性与性别之间的关系有了更深刻的理解。

Males and females are similar in some ways and different in others. Differences may arise because one sex is subject to greater reproductive competition (sexual selection) or because the sexes differ in their ecology (natural selection). Because males and females share a common genome, they are also subject to correlated responses to selection, which occur when genetic variants favored by selection in one sex ('like father, like son') are carried along in the other sex ('like father, like daughter'). Correlated responses may serve as an evolutionary constraint if the attributes that are beneficial to one sex are disadvantageous to the other sex. Steroid hormones are among the proximate mechanisms that lead to sex differences. They may act early in development to organize tissues or later in life to activate trait expression. When hormonal effects are similar in males and females, there is potential for correlated responses to selection. The focus of this proposal is the steroid hormone testosterone (T) and its integrating effect on sex differences in adult males and females of a songbird species, the dark-eyed junco. The research has four objectives. The first is to experimentally elevate testosterone (T) in females and measure its effect on the female's phenotype (e.g. appearance, behavior). The second is to determine whether elevated T is adaptive or maladaptive in females. The third is to assess the potential for correlated responses within and between the sexes by measuring change in T after exposure to a fixed dose of a hormonal stimulant (GnRH). The fourth is to assess sexual independence by comparing the role of T in the activation of aggressive behavior in males and females. Research described in this proposal will add to an already impressive 20-year database, provide opportunities for training future scientists of diverse backgrounds in the conduct of cybernetics, and laboratory and field experiments that address the integration of proximate and ultimate explanations for biological differences. This extensive database will provide fodder for continued synthesis, compilation, and cyber exploitation, and will make a significant contribution to this principle investigator's work, her collaborators, and others who will have access to this gold mine. This cyber research program will also enrich courses taught at Indiana University and elsewhere. Potential societal implications of the findings to be expected include: (1) the impact of hormonally active agents in the environment; and (2) a greater understanding of the relationship between sex and gender.