Quantitative Genetics of Foraging and Predator Avoidance in Anuran Tadpoles

自然界中的大多数生物都面临着一种相互矛盾的需求，既要努力为自己获取足够的食物，又要努力不成为其他生物（如捕食者）的食物。因为获取资源和躲避捕食者都分别有助于生长和生存，这两种表现指标之间的冲突通常会导致两个重要适应度组成部分之间的权衡。这种权衡经常用现象学术语来描述，但是，就像生物体的许多重要生态特征一样，其潜在的功能和遗传决定因素是未知的。因此，我们对哪些性状影响生长和躲避捕食者所知甚少，因此我们对这些性状网络的进化几乎一无所知。在这篇论文中，我们描述了研究牛蛙和绿蛙蝌蚪（无尾目：蛙科）的表型和遗传结构特征，这些特征被认为决定了它们的生长和捕食者的躲避。牛蛙（Rana catesbiana）和绿蛙（Rana clamitans）的亲缘关系最为密切，它们倾向于在不同捕食者的栖息地分开生活。牛蛙主要出现在支持食肉鱼类的湖泊中，而绿蛙主要出现在不支持鱼类但支持食肉蜻蜓和蝾螈的池塘中。这种分离似乎受到两个物种在活动水平、觅食水平以及对掠食性鱼类和蜻蜓的防御能力方面的差异的强烈影响。因此，这对物种提供了一个极好的机会：1)确定决定一对近亲物种生长和捕食者躲避成功的特性；2)研究这些特性的变异模式如何随着这些物种适应各自的环境而变化；3)探索这些特性的进化动力学并预测它们对自然选择的反应。为了做到这一点，我们将进行两个主要的实验，这两个实验都是在物种，种群和个体水平上检查生长和抗捕食者性能的变化。在第一个实验中，我们将测量一系列行为和形态特征，我们假设这些特征与生长和抵抗捕食者的成功有关。我们将对每个物种的6个种群的大量个体进行这些测量，并检查性状之间的变化模式。在第二个实验中，我们将在每个物种的单个种群中估计大多数这些性状的遗传变异和遗传能力的大小和模式。分析将测试关于表型进化的功能和遗传限制的假设，以及在适应不同环境的过程中性状之间的偶联是如何变化的。

McPeek9806293Most organisms in nature are faced with the conflicting demands of trying to acquire enough food for themselves while simultaneously trying not to become food for some other organism (e.g., a predator). Because both resource acquisition and predator avoidance contribute to growth and survival, respectively, the conflict between these two performance measures usually causes a trade-off between two important fitness components. This trade-off has been frequently described in phenomenological terms but, like many ecologically-important features of organisms, its underlying functional and genetic determinants are unknown. Consequently, we know very little about what characters actually influence growth and predator avoidance, and thus we know almost nothing about the evolution of such networks of characters. In this proposal, we describe research to examine the phenotypic and genetic architecture of characters that are hypothesized to determine growth and predator avoidance in bullfrog and green frog tadpoles (Anura: Ranidae). Bullfrogs (Rana catesbiana) and green frogs (Rana clamitans) are most closely related to one another, and they tend to segregate between habitats with different suites of predators. Bullfrogs occur primarily in lakes that support predatory fish, while green frogs occur primarily in ponds that do not support fish but do support predatory dragonflies and salamanders. This segregation appears to be strongly influenced by differences between the two species in their levels of activity, foraging, and their defenses against predatory fish and dragonflies.This pair of species, therefore, offers an excellent opportunity to 1) identify the properties that determine growth and predator avoidance success in a pair of closely related species, 2) examine how the patterns of variation in these properties have changed as these species have adapted to their respective environments, and 3) explore the evolutionary dynamics of these traits and predict their responses to natural selection. To do this, we will conduct two major experiments, both of which examine variation in growth and antipredator performance at the species, population, and individual levels. In the first experiment, we will measure a suite of behavioral and morphological characters that we hypothesize are related to growth and antipredator success. We will make these measurements on a large number of individuals from six populations of each species, and examine patterns of variation among traits. In the second experiment, we will estimate magnitudes and patterns of genetic variation and heritability for most of these traits in a single population of each species. Analyses will test hypotheses about functional and genetic constraints on phenotypic evolution and how couplings among characters have changed during adaptation to different environments.