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

性选择是进化生物学的一个中心话题，自从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，并被用来评估竞争对手或潜在配偶的质量。为了理解这些装饰品是如何进化和维持的，我们不仅需要识别广告中的品质类型，还要识别防止作弊的机制。如果性信号是可靠的，信号的产生或维护应该是昂贵的。在许多物种中，睾丸激素增强了装饰物的表达，但代价高昂，因为它降低了个体科普寄生虫的能力。根据“免疫能力障碍假说”，睾丸激素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，我们更不知道个体的遗传质量如何影响寄生虫抗性和寄生虫抗性之间的权衡。与拟议的工作，我的目标是了解障碍机制如何运作，以确保诚实的信号通过睾丸激素依赖的装饰品，以及个人的遗传背景如何缓和关键激素对寄生虫抗性的影响，从而影响性取向的水平。我将重点介绍两种激素（睾酮和皮质酮）对免疫和免疫功能的双重影响。我也将集中在主要组织相容性复合体（MHC）基因，这是越来越多地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，寄生虫抗性和性取向之间的权衡。

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.