Dissertation Research: Evolution and Development of Alternative Amphibian Morphologies

论文研究：替代两栖动物形态的进化和发展

• 批准号: 8800986
• 负责人: Mark Kirkpatrick
• 金额: $ 0.55万
• 依托单位: University of Texas at Austin
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1988
• 资助国家: 美国
• 起止时间: 1988-06-15 至 1990-11-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=8800986&HistoricalAwards=false
• 关键词: Dissertation; Research; Evolution; Development; Alternative

Under the concept of natural selection, individuals should respond to their environment in such a way as to increase their genetic fitness. Individuals in a population may respond differently, however, to identical environmental conditions; there are often alternative, equally adaptive responses to selection pressure. The proposed research will study spadefoot tadpoles which occur as two discrete phenotypes: a large, rapidly developing carnivore morph and a smaller, slower developing omnivore morph. This system provides a unique opportunity to examine how an animal's ecology can profoundly affect its development. The system poses interesting problems on the population level as well. The first goal of this study will be to ascertain how the dimorphism is maintained evolutionarily. Carnivores appear to do better in highly ephemeral pools (because of their more rapid development), but omnivores may do better in more permanent ponds (because of their greater postmetamorphic survivorship and reduced susceptibility to carnivore predation). The hypothesis that these fitness trade-offs balance will be tested by examining whether survivorship (both pre- and postmetamorphic) of the two morphs is equal within a given pond. If this experiment shows that the two morphs do equally well, this would provide the opportunity to analyze the strategies of development. The second goal is to explain what factors favor the spread of this and other similar dimorphisms. Research will be done on the extent to which this variability represents genetic adaptation to different environmental conditions at opposite ends of the species' range as opposed to environmentally induced phenotypic variation. The third goal is to explain the physiological basis of morph determination. Whether the ingestion of naturally occurring thyroxine (the endocrine "trigger" of amphibian differentiation at metamorphosis) causes young tadpoles to develop into carnivores will be examined. If thyroxine is the trigger of morph differentiation, the underlying physiological mechanisms will be studied. This study will provide much needed information, at both the proximate and ultimate levels, concerning how alternative strategies of development can persist in a population. Scaphiopus with its dimorphic tadpole is an excellent model animal for studying the evolution of developmental plasticity. The results of this study may have potential applications. Tadpoles have long been used in the study of animal development and spadefoots may provide developmental biologists with a unique opportunity to study large scale facultative shifts in development in a vertebrate. Finally, the carnivore's ability to switch to omnivory has already interested a German scientist attempting to increase yields in commercial fish hatcheries, where fish are typically fed a more expensive carnivorous diet.

在自然选择的概念下，个人应以提高遗传健康的方式对环境做出反应。 但是，人口中的个人对相同的环境条件的反应可能有所不同。 通常有对选择压力的替代性，同样适应性的反应。 拟议的研究将研究以两种离散表型出现的Spadefoot t骨：一种大型，快速发展的食肉动物变形，并且较小，较较慢的杂食变体。 该系统提供了一个独特的机会，可以研究动物的生态学如何深刻影响其发展。 该系统在人群层面也提出了有趣的问题。 这项研究的第一个目标是确定如何在进化上保持二态性。 食肉动物似乎在高度短暂的池中表现更好（因为它们的发展迅速），但杂食动物在更永久的池塘中的表现可能更好（因为它们具有更大的形成后生存和降低食肉动物捕食的敏感性）。 通过研究两个形态的生存（既有前和后型）的生存权（既有成像和后型）在给定的池塘内是否相等，可以通过检查这些健身权衡平衡的假设。 如果该实验表明这两个形态的表现同样出色，那么这将提供分析发展策略的机会。 第二个目标是解释哪些因素有利于这种和其他类似二态性的传播。 研究将在该物种范围相对范围内的不同环境条件的遗传适应与环境诱导的表型变化相对的程度上进行研究。 第三个目标是解释变体确定的生理基础。 是否会检查摄入天然发生的甲状腺素（变态时两栖分化的内分泌“触发”）是否会导致年轻t骨出现成食肉动物。如果甲状腺素是变形分化的触发因素，将研究基本的生理机制。 这项研究将在近端和最终层面上提供急需的信息，以了解替代性发展策略如何在人群中持续存在。 Scaphiopus及其二态t是研究发育可塑性进化的出色模型动物。 这项研究的结果可能具有潜在的应用。 长期以来，t一直在研究动物发育中，Spadefoots可能会为发育生物学家提供一个独特的机会来研究脊椎动物中发育的大规模兼职转变。 最后，食肉动物转向杂食的能力已经使德国科学家试图提高商业鱼类孵化场的产量，那里的鱼类通常会喂食更昂贵的食肉饮食。