Recombinant traits and recombinant mating preferences in hybrid zones

查尔斯·达尔文在他的《物种起源》中最纠结的一件事就是雄性动物身上显眼的装饰物的明显悖论。当这些奢侈的建筑既昂贵又危险时，它们怎么能在自然选择中得到青睐呢？达尔文认为，雄性进化出明显的特征，以满足雌性的“审美趣味”，从而使有装饰的雄性获得交配优势。然而，自达尔文时代以来，我们已经对这种性选择是如何在不太可能的情况下进行的，即雄性只有一个吸引人的装饰（如长尾巴），雌性只有一个交配偏好（长尾巴）。然而，如果雄性是两性二态的——外表与雌性不同——它们几乎总是华丽的，具有一系列针对不同感官的显著特征。雌性如何将这些信息整合到与谁交配的决定中？这些决定又如何影响显著阵列的进化呢？这个问题是理解性选择以及新物种如何形成和维持的基础。该项目将利用自然界的一个显著现象来解决这个问题：墨西哥高地的溪流中有两种剑尾鱼（剑尾鱼科：剑尾鱼科：birchmanni和X. malinche）杂交，形成一个杂交区。为什么雌性会与“错误”的物种交配——是她们对美丽的品味导致了她们犯错吗？一个物种的雌性比另一个物种更容易犯这样的错误吗？为了解决这些问题，有关野生动物DNA标记分布的数据将与各种测量雌性交配偏好的技术相结合。电脑制作的雄性求爱行为的动画电影可以展示任何一组视觉特征；因此，女性的偏好可以通过任何一种特征的组合来衡量。这些研究将揭示野生动物对特定种类雄性的偏好选择程度，以及基因之间的相互作用如何抵消雌性配偶选择对雄性性特征进化的影响。该项目在三个主要领域提供了独特的推广机会。(1)与墨西哥科学家合作，通过联合培训学生，并与墨西哥已建立的实验室继续合作；(2)通过针对双语拉美裔学生的暑期研究项目培训少数民族本科生；(3)通过与当地基层组织合作，促进淡水资源的可持续利用，向当地社区推广。

One of the things Charles Darwin struggled with most in his Origin of Species was the apparent paradox of conspicuous ornaments in male animals. How could such extravagant structures be favored by natural selection when they are both costly to produce and dangerous to exhibit? Darwin suggested that males evolve conspicuous traits to satisfy females' "taste for the beautiful", giving ornamented males a mating advantage. Since Darwin's time, though, we have developed a sophisticated understanding of how such sexual selection operates in the unlikely case of males with a single attractive ornament (like a long tail) and females with a single mating preference (for long tails). Yet if males are sexually dimorphic - externally different from females - they are almost always flamboyant, with an array of conspicuous traits targeting different senses. How does a female integrate information about such an array into a decision about whom to mate with; and how do such decisions affect the evolution of conspicuous arrays? This question is fundamental to understanding sexual selection, as well as how new species are formed and maintained. This project will address this question by taking advantage of a remarkable phenomenon in nature: streams in highland Mexico where two species of swordtail fish (family Poeciliidae: Xiphophorus birchmanni and X. malinche) interbreed, forming a hybrid zone. Why do females mate with the "wrong" species - does their taste for the beautiful cause them to make mistakes? Are females of one species more likely than the other to make such mistakes? To address these questions, data on the distribution of DNA markers in the wild will be combined with a variety of techniques for measuring female mating preferences. Computer-animated movies of males performing courtship behavior can be created to display any set of visual characteristics; female preferences can thus be measured for any combination of traits of either. These will reveal the extent to which preferences select for particular kinds of males in the wild, as well as how interactions among genes can counteract the effects of female mate choice on the evolution of male sexual traits. This project provides unique opportunities for outreach in three main areas. (1) Collaboration with Mexican scientists through joint training of students and through continued work with an established lab in Mexico, (2) Training of minority undergraduates via a summer research program targeted at bilingual, Latino students, and (3) Local community outreach, through working with a local grassroots organization to promote sustainable use of freshwater resources.