Behavioral Dysfunction and the Evolution of Reproductive Isolation between Species

不同物种的繁殖被称为杂交，这是一种常见的现象，它提出了一个根本问题：如果物种可以杂交，是什么保持了它们的鲜明特征，并将物种分开？这个问题的答案通常集中在杂交后代身上：如果杂交后代不能存活或繁殖，那么物种之间的基因交换将受到限制，物种将保持分离和区分。到目前为止，大多数探索杂种表现不佳的可能性的工作都集中在杂交生理和形态上。很少有研究调查杂交种是否表现出阻止其繁殖的改变行为，从而限制进一步的基因交换。这项拟议的工作评估了行为对铲足蟾蜍物种杂交的影响。通过这样做，这项研究将为行为如何帮助维持物种边界提供重要的见解。这项研究对于理解生物多样性和保护可能与其他物种杂交的濒危物种具有重要意义。在开展这项工作时，国际和平研究所将对本科生和研究生进行研究技巧和公众宣传方面的培训。事实上，PI和她的实验室成员将通过在北卡罗来纳州自然科学博物馆的工作，在北卡罗来纳州和其他地方进行公共宣传。具体地说，他们将在博物馆的每日星球剧院进行演讲，该剧院为博物馆参观者提供现场节目，并向整个北卡罗来纳州的K-12学校、老年中心和图书馆提供现场演示。这些演讲的视频以播客的形式上传到iTunes大学和博物馆的网站上，博物馆每月有2万次下载，博物馆的网站每年有大约100万的点击量；通过博物馆网站分发的节目可以在任何地方向用户提供。在广泛使用的生物物种概念下，物种被定义为不交换基因的有机体的群体；它们拥有阻止基因在它们之间流动的进化特征。这类“隔离机制”的一大类包括在杂交后代中产生低适合度的特征，从而阻止他们与亲本群体回交。由于杂交适应不良对物种形成过程至关重要，澄清杂交适应不良的原因是理解物种形成的核心。大多数物种形成研究集中在杂交适应不良的三个原因上：存活率下降，生育力下降，以及在亲本生态位中成功的可能性降低。相比之下，行为在杂交种适应不良中的作用，特别是杂交种可能表现出功能失调的生殖行为，一直被研究得相对较少。然而，存活的、有生育能力的杂交后代可能不会对求爱信号做出适当的反应，或者，它们可能会表达出配偶偏好，从而降低它们与增强健康的配偶交配的可能性。这种功能失调的生殖行为可能会使可存活的、可育的杂交后代“行为不育”，从而成为物种之间潜在的关键隔离机制。这项拟议的工作将确定杂交叉脚蟾蜍是否表现出功能失调的生殖行为，以及这种行为是否解释了自然种群中的基因交换模式。使用两种自然杂交的蟾蜍，研究将：1)评估杂交对繁殖机会的反应；2)建立杂交配偶偏好；3)测量配偶偏好的适合度结果；4)确定杂交是否在繁殖上投资较少；以及5)确定田间杂交交配的模式。这些项目将共同确定行为在物种边界起源和维持中的作用。

The breeding of different species, called hybridization, is a common phenomenon that raises a fundamental problem: if species can interbreed, what maintains their distinct characteristics and keeps species separated? Answers to this question have usually focused on hybrid offspring: if hybrids cannot survive or reproduce, then gene exchange between species will be restricted and species are kept separate and distinct. To date, most work exploring the possibility that hybrids perform poorly focuses on hybrid physiology and morphology. Few studies have investigated whether hybrids show altered behaviors that prevent them from reproducing and thereby limiting further gene exchange. The proposed work evaluates the impact of behavior on hybridization in spadefoot toad species. By doing so, the research will provide important insights into how behavior acts to help maintain species boundaries. The research has critical implications for understanding biodiversity and conservation of endangered species that could hybridize with others. In carrying out this work, the PI will train undergraduates and graduate students in both research techniques and public outreach. Indeed, the PI and her lab members will engage in public outreach in North Carolina and beyond through work at the North Carolina Museum of Natural Sciences. Specifically, they will give talks in the museum's Daily Planet Theater, which provides live programming to museum visitors and live streaming of presentations to K-12 schools, senior centers, and libraries throughout North Carolina. Videos of these presentations are uploaded as podcasts onto iTunes University, on which the museum receives 20,000 downloads a month, and to the museum's website, which receives approximately one million hits per year; programs distributed via the museums website are available to users anywhere.Under the widely used biological species concept, species are defined as groups of organisms that do not exchange genes; they possess evolved features that prevent gene flow between them. A major class of such 'isolating mechanisms' includes traits that engender low fitness in hybrid offspring, thereby preventing them from backcrossing to the parent populations. Because hybrid maladaptation is crucial to the speciation process, clarifying the causes of hybrid maladaptation is central to understanding speciation. Most speciation research has focused on three causes of hybrid maladaptation: decreased survival, reduced fertility, and decreased likelihood of succeeding in either parental niche. In contrast, the role of behavior in hybrid maladaptation, specifically that hybrids might exhibit dysfunctional reproductive behavior, has been relatively understudied. Yet, viable, fertile hybrids might fail to respond appropriately to courtship signals, or, alternatively, they might express mate preferences that reduce their likelihood of mating with fitness-enhancing mates. Such dysfunctional reproductive behavior could render viable, fertile hybrids 'behaviorally sterile', thereby acting as a potentially key isolating mechanism between species. The proposed work will ascertain if hybrid spadefoot toads display dysfunctional reproductive behaviors, and whether such behavior explains patterns of gene exchange in natural populations. Using two species of naturally hybridizing toads, the research will: 1) evaluate hybrid responses to breeding opportunities; 2) establish hybrid mate preferences; 3) measure the fitness consequences of mate preferences; 4) ascertain whether hybrids invest less in reproduction; and 5) determine patterns of hybrid mating in the field. Together, the projects will identify behavior's role in the origins and maintenance of species boundaries.