Recombinant traits and recombinant mating preferences in hybrid zones

查尔斯·达尔文在他的《物种起源》一书中最纠结的一件事是雄性动物身上明显的装饰物的悖论。这种奢华的建筑怎么会受到自然选择的青睐，因为它们的制造成本很高，展示起来也很危险？达尔文认为，雄性进化出明显的特征来满足雌性的“美的品味”，从而使有装饰品的雄性具有交配优势。然而，自达尔文时代以来，我们已经对这种性选择如何在雄性只有一个迷人的装饰品(比如长尾)和雌性有单一交配偏好(长尾)的不太可能的情况下进行了复杂的理解。然而，如果男性具有两面性--外表与女性不同--他们几乎总是很张扬，有一系列针对不同感官的明显特征。雌性如何将关于这样一个阵列的信息整合到与谁交配的决定中；这样的决定如何影响显眼阵列的进化？这个问题对于理解性选择以及新物种是如何形成和维持的是基本的。该项目将利用自然界的一个显著现象来解决这一问题：墨西哥高原的溪流，在那里两种剑尾鱼(剑鱼科：剑尾鱼X.Malinche)杂交繁殖，形成一个杂交区。为什么雌性会与“错误的”物种交配--她们对美的品味会导致她们犯错吗？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，有关野外DNA标记分布的数据将与测量雌性交配偏好的各种技术相结合。用电脑制作的男性求爱行为的动画电影可以显示任何一组视觉特征；因此，女性的偏好可以根据其中任何一种特征的任何组合来衡量。这些将揭示在野外对特定类型雄性的偏好选择的程度，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征进化的影响。该项目在三个主要领域提供了独特的外联机会。(1)通过联合培训学生，并通过与墨西哥一个已建立的实验室的持续合作，与墨西哥科学家开展合作；(2)通过针对双语拉丁裔学生的暑期研究项目，对少数族裔本科生进行培训；(3)通过与当地基层组织合作，促进淡水资源的可持续利用，对当地社区进行外联。

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.