DISSERTATION RESEARCH: Forging a Context for Female Mate Choice for Carotenoid Ornaments

本研究项目的首要目标是促进对动物纹饰进化的理解。在动物王国里，鸟类拥有一些最精致的歌曲、舞蹈和色彩，人们普遍认为，这些表演是在雌性选择配偶时对雌性偏好的反应中进化出来的。然而，形成观赏性状的具体过程仍然存在争议。特别是，目前的理论提出，许多鸟类的装饰物中黄到红的颜色是质量的真实信号，但将装饰物表达与质量联系起来的机制，以及装饰物为选择雌性提供的信息内容，仍不清楚。该研究项目将提供关键的测试，以了解彩色色素与一种鸣禽——国内金丝雀（Serinus canaria）的彩色装饰质量和生理状况之间的关系。另一组实验将研究雄性金丝雀的两种明显信号——鲜艳的颜色和复杂的歌声——如何相互作用，影响雌性的择偶选择。使用一个能够很好地适应圈养的物种，可以在不使鸟类受到笼子压力的情况下对实验变量进行特别精细的控制，并且进一步允许使用活金丝雀作为“科学大使”的一系列推广活动，这些活动既面向全国的金丝雀饲养爱好者，也面向阿拉巴马州的年轻学生。虽然许多行为学研究已经对以类胡萝卜素为基础的着色的性选择进行了研究，但对于类胡萝卜素如何与信号诚实联系在一起，以及条件依赖性信号如何影响女性的偏好，尚无共识。本研究项目包括两组互补的实验，评估信号诚实的机制基础和颜色信号的最终功能。本研究将利用国内金丝雀（Serinus canaria）的高适应性圈养系统，通过严格的实验控制来解决这些问题。最初的实验将检验类胡萝卜素饰品条件依赖的机制基础，通过测试关于分配权衡在维持信号诚实中的作用的基本假设。具体来说，研究人员将使用具有消除类胡萝卜素吸收或分配的敲除突变的金丝雀来检查循环类胡萝卜素的益处以及以一种受控的方式将其分配给羽毛的潜在成本，这在其他系统中是不可能的。虽然这些实验将产生关于维持信号诚实的近似机制的信息，但弥合机制和功能之间的差距将大大提高这一核心研究对理解动物行为的重要性。因此，第二组实验将采用一种新的配偶选择实验设计，严格控制雄性展示表型，以检验类胡萝卜素颜色的条件依赖性表达是否是雌性偏好的目标。这些测试将通过评估基于类胡萝卜素的羽毛颜色如何影响作为整体多模态鸣禽展示的组成部分的配偶选择，为第一次实验中研究的机制建立最终的行为背景。

The overarching goal of this research project is to advance understanding of the evolution of animal ornamentation. Birds feature some of the most elaborate songs, dances, and colors of the animal kingdom, and such displays are generally accepted to have evolved in response to female preferences during mate choice. However, the specific processes that have shaped the ornamental traits remain contentious. In particular, current theory proposes that the yellow-to-red coloration in the ornaments of many bird species is an honest signal of quality, but the mechanisms linking ornament expression to quality, and hence the information content that ornaments present to choosing females, remain unclear. This research project will provide critical tests of how colorful pigments relate to the quality of both colored ornaments and physiological condition in a songbird species, the domestic canary (Serinus canaria). An additional set of experiments will then investigate how the two conspicuous signals of the male canary--brilliant coloration and complex song--interact to shape female mate choice. Using a species that is well-adjusted to captivity enables particularly fine control over experimental variables without subjecting the birds to cage stress, and further allows for a suite of outreach activities using live canaries as "science ambassadors" both to hobbyist canary breeders nationwide and young students across the state of Alabama.While many behavioral studies have examined sexual selection for carotenoid-based coloration, there is no consensus for how carotenoid pigments link to signal honesty and how condition-dependent signals shape female preferences. This research project comprises two complementary sets of experiments assessing both the mechanistic basis of signal honesty and the ultimate function of color signals. The research will address these questions with tight experimental control using the highly amenable captive system of the domestic canary (Serinus canaria). Initial experiments will examine the mechanistic basis for condition-dependence in carotenoid-based ornaments by testing fundamental assumptions about the role of allocation tradeoffs in maintaining signal honesty. Specifically, the researchers will use canaries with knockout mutations that eliminate carotenoid absorption or allocation to examine the benefit of circulating carotenoids and the potential cost of their allocation to plumage in a controlled manner that is not possible in other systems. While these experiments will yield information about the proximate mechanisms that maintain signal honesty, bridging the gap between mechanism and function will greatly advance the importance of this core research to understanding animal behavior. Therefore, the second set of experiments will use a novel mate-choice experimental design with tight control over male display phenotype to examine whether the condition-dependent expression of carotenoid coloration is the target of female preference. These tests will establish the ultimate behavioral context for the mechanism studied in the first experiments by assessing how carotenoid-based plumage coloration impacts mate choice as a component of the overall multimodal songbird display.