Endocrine-immune function trade-offs, genetic quality and honest sexual signalling

性选择是进化生物学中的一个中心话题，自达尔文的开创性工作以来，它一直吸引着生态学家。许多物种拥有色彩鲜艳或夸张的装饰物，这些装饰物是通过性选择进化而来的，用于评估竞争对手或潜在伴侣的质量。为了理解这些装饰是如何演变和维持的，我们不仅需要确定所宣传的品质类型，还需要确定防止欺骗的机制。如果性信号是可靠的，信号的产生或维持应该是昂贵的。在许多物种中，睾酮可以增强装饰物的表达，但代价高昂，因为它降低了个体应对寄生虫的能力。根据“免疫能力障碍假说”，睾酮的这种双重作用可以防止作弊。然而，睾丸激素影响寄生虫抗性的确切机制仍然知之甚少，我们对个体的遗传质量如何影响装饰和寄生虫抗性之间的权衡了解得更少。通过提出的工作，我的目标是了解残疾机制是如何运作的，以确保通过睾酮依赖性装饰的诚实信号，以及个体的遗传背景如何调节关键激素对寄生虫抗性的影响，从而影响性装饰的水平。我将重点讨论两种激素（睾酮和皮质酮）对纹饰和免疫功能的双重影响。我还将重点关注主要组织相容性复合体（MHC）基因，它越来越被认为是性选择研究的范例。我将研究MHC基因型如何影响激素、寄生虫抗性和性装饰之间的权衡。

Sexual selection is a central topic in evolutionary biology, and has fascinated ecologist since the pioneering work of Darwin. Many species possess brightly coloured or exaggerated ornaments that evolved via sexual selection and are used to assess the quality of rivals or potential mates. To understand how these ornaments evolved and are maintained, we need to identify not only the type of qualities that are advertised, but also the mechanisms that prevent cheating. If sexual signalling is to be reliable, signal production or maintenance should be costly. In many species, testosterone enhances the expression of ornaments, but is costly, because it reduces an individual's ability to cope with parasites. According to the 'Immunocompetence Handicap Hypothesis', this dual action of testosterone would prevent cheating. However, the exact mechanisms by which testosterone influences parasite resistance are still little known, and we know even less about how an individual's genetic quality influences the trade-offs between ornamentation and parasite resistance. With the proposed work, my aim is to understand how handicap mechanisms operate to ensure honest signalling via testosterone dependent ornaments, and how the genetic background of individuals moderates the effects of key hormones on parasite resistance, thereby influencing levels of sexual ornamentation. I will focus on the dual effects of two hormones (testosterone and corticosterone) on ornamentation and immune function. I will also focus on Major Histocompatibility Complex (MHC) genes, which are increasingly recognized as a paradigm in studies of sexual selection. I will investigate how MHC genotype influences the trade-offs between hormones, parasite resistance and sexual ornamentation.