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

生命早期是一个关键阶段，在此期间所经历的环境可能对一个人的一生产生重要的影响。了解个体基因和早期发育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成熟的进化和行为研究系统来确定发育环境是如何塑造一种特征的表达的，这种特征对以后的生活中繁殖成功至关重要。具体而言，本研究将在早期发育过程中操纵巢寄生虫（环境的重要组成部分），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，在这里是一种棕红色的黑色素颜色，是一种用于两性交流的重要信号，它受到早期生活条件的影响，因此也受到个体繁殖成功率的影响。在生长羽毛的组织中表达的基因将被测量，以确定其表达受环境条件影响的特定基因。这项工作的结果将提供广泛的信息，因为黑色素是各种动物的外观和颜色的共同色素。然而，环境如何与基因相互作用来影响黑色素的形成还不是很清楚。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，以及制定将在公立中学实施并在科学教学研讨会上与教师广泛分享的教案。女性对男性颜色的偏好被认为是适应性的，因为这些男性特征传达了潜在的信息。传统上认为，基于黑色素的颜色特征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发育早期。如果是这样，性状变异可能提供有关个体发育历史的信息。先前的研究表明，家燕黑色素颜色的变化几乎完全（70%）是由于早期环境的差异，羽毛的颜色提供了雄性领地外寄生虫负荷的信息。螨虫影响雏鸟的生存、生长、免疫力和基于黑色素的羽毛颜色。本项目将通过交叉培养卵和操纵螨虫来梳理基因和环境质量的作用，从而确定与颜色变化相关的基因表达差异。将收集发育中的羽毛，并量化RNA表达，以了解早期环境如何与黑色素途径中的基因相互作用，从而影响基于黑色素的信号的终身表达。该研究将对了解基于黑色素的观赏性状在发育早期的环境相互作用中的基因，从而了解雌性通过这些性状获得的信息具有重要意义。这项工作的结果将提供一个更清晰的图像，以黑色素为基础的性状是如何在许多层面上与环境相互作用的：从详细的基因表达，到终生的性状表达，到种群内的变异，以及这与寄生虫群落的关系，最后是涉及生殖隔离的种群间不同的形态性状。

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.