Doctoral Dissertation Research: Androgyny & Androgens in Females: Relating Hormones to the Evolution of Sexual Dimorphism

当最佳表型因性别而异时，性别差异或性二型性的进化是可以预期的。然而，在许多物种中，二型性的程度是温和的，许多个体表现出介于雄性和雌性规范之间的特征，例如身体大小或行为。这个群体中的女性，被称为雌雄同体的女性，是有趣的，因为他们提供了一个自然的实验，了解性二型性的来源和后果。激素暴露的变化，特别是雄激素，如睾酮，是脊椎动物性别差异发展的主要机制。这种变异也可能介导雌雄同体性状在性别内的表达，导致雄性样性状之间的协变，例如大雌性也可能是攻击性雌性。 如果类雄雌虫在生存或繁殖方面与典型雌虫不同，则性二型性的程度可能会降低或增强。 本项目旨在确定在一个性状（形态或行为）中表达的双性化程度是否与其他性状中的双性化水平相关，这将表明控制性状表达的共同机制。 此外，该项目将努力确定在发育期间或成年期的雄激素暴露是否驱动这种协变，以及雌雄同体女性在生存或生殖成功方面是否与典型女性不同。这些问题的答案将使我们了解女性的社会行为，形态和激素暴露水平之间的潜在联系，以及由激素介导的复杂特征的演变。这项工作将与自由生活的鸣禽完成，并有助于培训本科生进行研究，作为培训计划的一部分，如NSF的本科生研究经验（REU）和印第安纳州大学的学生成就研究和奖学金（STARS）计划。

When the optimal phenotype differs by sex, the evolution of sex differences, or sexual dimorphism, is expected. In many species, however, the degree of dimorphism is mild, and numerous individuals express traits, e.g. body size or behavior, that fall between male and female norms. Females in this group, known as androgynous females, are of interest because they offer a natural experiment for understanding the sources and consequences of sexual dimorphism. Variation in hormone exposure, especially androgens like testosterone, is a primary mechanism for the development of sex differences in vertebrates. This variation may also mediate the expression of androgynous traits within a sex, leading to covariation among male-like traits, e.g. big females may also be aggressive females. If male-like females differ from typical females in survival or reproduction, the degree of sexual dimorphism may reduced or enhanced. This project seeks to determine whether the degree androgyny expressed in one trait (morphology or behavior) is related to the level of androgyny in other traits, which would indicate a common mechanism controlling trait expression. Additionally this project will strive to determine whether androgen exposure during development or in adulthood is driving this covariation, and also whether androgynous females vary from typical females in survival or reproductive success. Answers to these questions will inform our understanding of the potential links between social behavior, morphology and hormone exposure levels in females as well as the evolution of complex traits that are mediated by hormones. This work will be done with free-living songbirds and serve to train undergraduates to conduct research as part of training programs such as NSF's Research Experience for Undergraduates (REU) and Indiana University's Student Achievement in Research and Scholarship (STARS) programs.