Recombinant traits and recombinant mating preferences in hybrid zones

查尔斯·达尔文在《物种起源》一书中最纠结的一件事就是雄性动物身上明显的装饰物这一明显的悖论。这种奢侈的结构怎么可能受到自然选择的青睐，因为它们的生产成本很高，展示起来也很危险？达尔文认为，雄性进化出明显的特征，以满足雌性的“审美”，从而使顺从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如何在不太可能的情况下运作有了一个复杂的理解，即雄性只有一个有吸引力的装饰（如长尾），而雌性只有一个交配偏好（长尾）。然而，如果雄性具有性二态性--从外表上看与雌性不同--它们几乎总是艳丽的，有一系列针对不同感官的显著特征。雌性是如何将关于这种阵列的信息整合到与谁交配的决定中的？这些决定又是如何影响显着阵列的进化的？这个问题对于理解性选择以及新物种如何形成和维持至关重要。本项目将通过利用自然界中的一个显著现象来解决这个问题：墨西哥高原的溪流中有两种剑尾鱼（Poeciliidae科：Xiphophorus birchmanni和X. malinche）杂交，形成杂交区。为什么雌性会与“错误”的物种交配--是它们对美的品味导致了它们犯错误吗？一个物种的雌性比另一个更容易犯这样的错误吗？为了解决这些问题，有关野生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。计算机制作的雄性动物求爱行为的动画可以显示任何一组视觉特征;因此，雌性动物的偏好可以通过任何一种特征的组合来测量。这些研究将揭示在何种程度上偏好选择特定种类的野生雄性，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外联机会。(1)与墨西哥科学家合作，通过联合培训学生和继续与墨西哥的一个实验室合作，（2）通过针对双语、拉丁裔学生的暑期研究计划培训少数民族大学生，以及（3）通过与当地基层组织合作，促进淡水资源的可持续利用。

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.