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

这一研究项目的首要目标是促进对动物纹饰演变的理解。鸟类以动物王国中一些最精致的歌曲、舞蹈和颜色为特色，这种展示通常被认为是在雌性选择配偶的过程中根据雌性的喜好而进化的。然而，形成这些装饰性特征的具体过程仍然存在争议。特别是，目前的理论认为，许多鸟类的饰品从黄到红是质量的真实信号，但将饰品的表达与质量联系起来的机制，从而使饰品呈现出选择雌性的信息内容，仍然不清楚。这项研究项目将对家养金丝雀(Serinus Canaria)的五颜六色的色素与有色饰品的质量和生理条件之间的关系进行关键测试。然后，另一组实验将调查雄性金丝雀的两个明显信号--鲜艳的色彩和复杂的歌声--如何相互作用来塑造雌性伴侣的选择。使用一种能很好地适应圈养的物种，可以在不让鸟儿受到笼子压力的情况下，对实验变量进行特别精细的控制，并进一步允许全国范围内的金丝雀爱好者和阿拉巴马州的年轻学生通过活体金丝雀进行一系列外展活动。虽然许多行为研究已经研究了基于胡萝卜素的性别选择，但对于类胡萝卜素如何与诚实联系在一起，以及条件依赖信号如何塑造雌性的偏好，还没有达成共识。这项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。这项研究将通过使用高度顺从的家养金丝雀(Serinus Canaria)圈养系统进行严格的实验控制来解决这些问题。最初的实验将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，来检验基于类胡萝卜素的装饰品中条件依赖的机制基础。具体地说，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中类胡萝卜素的好处，以及它们以受控方式分配到羽毛的潜在成本，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最接近机制的信息，但弥合机制和功能之间的差距将极大地促进这一核心研究对理解动物行为的重要性。因此，第二组实验将使用一种新的配偶选择实验设计，严格控制男性的显示表型，以检验类胡萝卜素着色的条件依赖性表达是否是女性偏好的目标。这些测试将为第一次实验中研究的机制建立最终的行为背景，方法是评估作为整体多模式鸣鸟展示的一个组成部分，基于胡萝卜素的羽毛着色如何影响配偶选择。

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.