Sexual Dimorphism and UV Signaling in Birds

鸟类的两性二态性和紫外线信号传导鸟类鲜艳的颜色在性选择和自然选择的研究中起着重要作用。在许多种类的鸟类中，雄性具有鲜艳的颜色，而雌性则是隐秘的。传统上，羽毛的性别二态性被解释为性选择（即交配成功）变化的结果。然而，有几个原因可以解释为什么这种解释可能是不充分的。首先，迄今为止所有的比较分析都依赖于人类观察者对羽毛颜色和亮度的主观评估，现在很明显，鸟类的视觉与人类完全不同。鸟类不仅能看到人类看不见的紫外线（UV）光谱，它们在人类可见光谱中也能看到不同的东西。不幸的是，目前还没有对鸟类的紫外线反射进行大规模的比较分析，因此尚不清楚紫外线信号是否普遍存在，或者这种信号是否在两性之间普遍存在差异。其次，最近对羽毛颜色性别差异的研究发现，羽毛的进化变化在雌性中比雄性更常见，这表明我们一直把注意力集中在错误的性别上。事实上，有很多情况下，两性都有鲜艳的颜色（例如，鹦鹉、经理鸟、巨嘴鸟），这表明选择对雌性和雄性都有作用。雌性鲜艳的羽毛可能受到雄性配偶选择的青睐，或者雌性之间在获得配偶或食物方面的攻击。此外，当雌雄同体全年保卫一块领地时，自然选择可能更青睐颜色鲜艳的雌性，或者颜色图案也参与了伪装。因此，除了雄性的性选择外，其他形式的选择似乎在鸟类羽毛图案的进化中也很重要。这项为期三年的研究将利用博物馆标本的客观颜色测量（光谱仪测量）来研究鸟类羽毛图案的演变和羽毛颜色的性别差异。我们将测量1031种鸟类两性的光谱反射率，这些物种在我们之前的鸟类二态性研究中使用过。在我们之前工作的基础上，这项研究将大大加深对鸟类信号和羽毛图案进化的理解，这是一个100多年来一直困扰着生物学家和非专业人士的主题。此外，这项研究将提供机会，训练学生比较方法，加强威斯康星大学的研究设施，并建立一个鸟类光谱数据网站，供其他研究人员和教师使用。

Lay Abstract for proposal #0215560Sexual dimorphism and UV signaling in birdsThe brilliant colors of birds have played a prominent role in the study of sexual and natural selection. In many species of birds males possess bright colors, while females are cryptic. This sexual dimorphism in plumage is traditionally explained as a consequence of variation in sexual selection (i.e., mating success). However, there are several reasons why this explanation may be inadequate. First, all comparative analyses to date have relied on subjective evaluations of plumage color and brightness by human observers, and it is now clear that birds see quite differently than humans. Not only do birds see in the ultraviolet (UV) spectrum to which humans are blind, they also see differently in the human visible spectrum. Unfortunately, there has not yet been a large-scale comparative analysis of UV reflectance in birds, so it is not known if UV signaling is widespread or if such signals commonly differ between the sexes. Second, recent studies of sexual differences in plumage color have found that evolutionary changes in plumage have been more common among females than males, suggesting that we have been focussing on the wrong sex. Indeed, there are many cases of bright colors in both sexes (e.g., parrots, tanagers, toucans) suggesting that selection has acted on females as well as males. Bright plumage in females may be favored by male mate choice or aggression between females over access to mates or food. In addition, natural selection may favor brightly colored females when both sexes defend a territory year-round or color patterns are involved in camouflage. Thus, other forms of selection besides sexual selection on males appear to be important in the evolution of avian plumage patterns.The three year study proposed here will examine the evolution of avian plumage patterns and sexual differences in plumage color using objective measures of color (spectrometer measurements) taken from museum specimens. We will measure spectral reflectance of both sexes of the1031 species used in our previous study of avian dimorphism. By building on our previous work, this study will lead to significantly deeper understanding of signaling in birds and the evolution of plumage patterns, a subject that has enthralled and perplexed both biologists and lay persons for over 100 years. In addition, this study will provide opportunities for training students in comparative methods, enhance research facilities at UWM and produce a web site with spectral data of birds that can be used by other researchers and teachers.