DISSERTATION RESEARCH: The Role of Early Environment in the Development of a Lifelong Mate Choice Signal: Melanin- Based Color in Barn Swallows

早期生活是一个关键阶段，在这个阶段，所经历的环境可以对一个人的一生产生重要的影响。了解个体发育早期的基因和环境之间的相互作用如何产生自然界中所见的变异是生物学中的一个重要问题。这项研究将利用一个完善的进化和行为研究研究系统来确定发育环境如何塑造对晚年生殖成功至关重要的特征的表达。具体地说，这项研究将在早期发育过程中操纵巢寄生虫，这是环境的一个重要组成部分，以确定寄生虫感染及其产生的免疫反应如何与鸟类羽毛颜色的基因相互作用。羽毛的颜色，这里是棕红色的黑色素，是两性交流中使用的重要信号，它受到早期生活条件的影响，因此个体的生殖成功。将对生长羽毛的组织中表达的基因进行测量，以识别其表达受环境条件影响的特定基因。这项工作的结果将是广泛的信息，因为黑色素是一种常见的色素，在各种动物的外观和颜色。然而，目前还不清楚环境如何与基因相互作用来影响黑色素着色的发展。更广泛的影响包括对本科生和中学教师进行科学研究方面的培训，以及创建教案，这些教案将在公立中学实施，并在科学教学车间广泛分享给教师。女性对男性肤色的偏好被认为是适应性的，因为这些男性特征所宣扬的潜在信息。传统上，基于黑色素的颜色特征被认为受到严格的基因控制。然而，某些黑色素性状的条件依赖性可能发生在早期发育过程中。如果是这样的话，特征变异可能会提供有关个体发展史的信息。先前的研究表明，谷仓燕子的黑色素颜色的变化几乎完全(70%)是由于早期环境的差异，而羽毛的颜色提供了有关雄性领土内体外寄生虫载量的信息。螨类影响雏鸟的存活、生长、免疫力和以黑色素为基础的羽毛颜色。该项目将通过杂交培养鸡蛋和操纵螨虫来梳理基因的作用和环境质量，从而识别与颜色变化相关的基因表达差异。将收集发育中的羽毛，并对RNA表达进行量化，以了解早期环境如何与黑色素途径中的基因相互作用，以影响基于黑色素的信号的终身表达。这项研究将对理解基于黑色素的观赏性状的早期发育阶段的基因与环境的交互作用，从而了解雌性通过利用这些性状获得的信息具有重要的意义。这项工作的结果将提供一个更清晰的图景，说明基于黑色素的性状在发育过程中如何在多个水平上与环境相互作用：从详细的基因表达，到终生性状表达，到种群内的变异，以及这与寄生虫群落的关系，最后到涉及生殖隔离的种群之间的不同形态特征。

Early life is a critical stage during which the environment experienced can have important life-long effects for an individual. Understanding how the interaction between an individual's genes and the environment during early development create the variation seen in nature is an important question in Biology. This research will leverage a well-established study system for evolutionary and behavioral research to determine how the developmental environment shapes the expression of a trait that is critical to reproductive success later in life. Specifically, this study will manipulate nest parasites, an important component of the environment, during early development to determine how parasite infections and the immune responses they generate interact with the genes that underlie plumage color in birds. Plumage color, here a brownish-red melanin coloration, is an important signal used in communication between the sexes and it is impacted by early life conditions, and therefore the reproductive success of an individual. Genes expressed in tissues where feathers are grown will be measured to allow for the identification of specific genes whose expression is influenced by environmental conditions. Results from this work will be broadly informative as melanin is a common pigment underlying appearance and coloration in various groups of animals. However, it is not well understood how the environment interacts with genes to influence the development of melanin coloration. Broader impacts include training undergraduates and middle-school teachers in scientific research, and the creation of lesson plans that will be implemented in public middle schools and shared broadly with teachers at science-teaching workshops.Female preferences for male coloration are thought to be adaptive because of the potential information advertised by these male traits. Melanin-based color traits are traditionally thought to be under strict genetic control. However, condition-dependence for some melanin traits may occur during early development. If so, trait variation may provide information about an individual's developmental history. Previous work has shown that variation in melanin-based color in barn swallows is due almost entirely (70%) to differences in early environment, and that plumage color provides information about ectoparasite loads in a male's territory. Mites affect nestling survival, growth, immunity, and melanin-based plumage color. This project will identify gene expression differences associated with color variation by cross-fostering eggs and manipulating mites to tease apart the roles of genes and environmental quality. Developing feathers will be collected and RNA expression will be quantified to understand how early environment interacts with genes in the melanin pathway to influence the life-long expression of a melanin-based signal. The research will have important implications for understanding the gene by environment interactions during the early developmental period for melanin-based ornamental traits, and thus, information that females gain by using these traits. Results from this work will provide a clearer picture of how melanin-based traits interact with the environment during development at many levels: from the detailed gene expression, to lifelong trait expression, to variation within a population and how this relates to the parasite community, and finally to divergent morphological traits across populations that are involved in reproductive isolation.