Dissertation Research: Endocrine Coupling of Sexually Dimorphic Display Morphology and Aggressive Display Behavior in Two Sister Species

在攻击性过程中，雄性经常在行为上宣扬信号特征。攻击性和用于发出攻击性信号的结构通常在进化上是相关的，但在蜥蜴物种中，它们可能是分离的。这项研究将确定性类固醇激素如何控制两种男性特有特征的发展：1)腹色斑块，2)用来向对手展示斑块的刻板攻击行为。这项工作将研究Scelopus的两个姐妹物种，一个有雄性斑块，另一个雄性在进化上失去了斑块。孵化后的荷尔蒙水平将被操纵，成年个体的斑块表达和攻击性都将被评分，以检验雄性斑块特征和攻击性的脱钩是由于物种对两者的激素控制的差异造成的。对幼体血液样本的分析将证实，改变后的幼体荷尔蒙水平在自然水平内。在许多脊椎动物中，性激素(睾酮、雌二醇)在发育和成年期发挥作用，产生性别差异。睾丸激素可以转化为雌激素，这会影响大脑中与攻击有关的区域的发育。睾酮还可以转化为5a-二氢睾酮，这通常会影响身体其他部位的男性特征的发育。如果物种在这些荷尔蒙水平上不同，就可能发生脱钩。例如，这些物种的雄性在这些睾酮转换所需的酶方面可能会有所不同。对于自然种群中控制攻击性差异的激素机制和信号结构的差异，人们知之甚少，因为大多数研究集中在近亲繁殖的实验室啮齿动物品系和驯养动物品种上。

During aggression males often behaviorally advertise signaling traits. Aggression and the structures used in signaling aggression usually are correlated evolutionarily, but among Sceloporus lizard species they can be decoupled. This study will determine how sex steroid hormones control the development of two such male-specific traits: 1) patches of abdominal color, and 2) stereotyped aggressive behavior used to display the patches to opponents. Work will study two Sceloporus sister-species, one with male patches and one in which males have evolutionarily lost the patches. Hatchling hormone levels will be manipulated, and both patch expression and aggression will be scored in adults to test the hypothesis that decoupling of the male patches trait and aggression arises from species differences in hormonal control of the two. Assays of hatchling blood samples will verify that the altered hatchling hormone levels are within natural levels.In many vertebrates, sex hormones (testosterone, estradiol) act during development and adulthood to produce differences between the sexes. Testosterone can be converted to estrogen, which influences development of brain regions involved in aggression. Testosterone also can be converted to 5a-dihydrotestosterone, which often affects development of male traits elsewhere in the body. Decoupling could occur if species vary in these hormonal levels. For example, males of these species may vary in the enzymes needed for these conversions of testosterone. Relatively little is known about the variation in the hormonal mechanisms controlling differences in aggression and in signaling structures in natural populations, as most research focuses on inbred laboratory strains of rodents and domesticated animal breeds.