The Genetic and Physiological Basis of Life Cycle Convergence

9509802生态学和进化生理学的突出问题之一是理解主要新特征进化的机制。特别是，当我们在两个或多个不相关的物种中看到相同的适应时，我们可能会问一个基本问题：“这些物种是利用相同的生理和遗传机制来解决它们的适应问题，还是使用不同的机制解决方案来实现相同的适应解决方案？”如果我们要了解生物体如何适应不断变化的环境，就需要对这个问题给出答案。为了解决这个问题，这项研究将使用来自墨西哥和美国的蝾螈物种模型组，这些物种已经改变了它们的生理变态途径：一些物种经历了正常的变态，而另一些物种则放弃变态，以性成熟的水生幼虫动物的形式完成它们的生活。几种策略，从负责变态的基因的分子分析，到调节变态完成的激素管理，将被用来确定在六种不同种类的蝾螈中实现这一重要生态生活史转变的机制。如果这一机制在所有物种中都是相同的，这将表明本质上只有一种生理和遗传机制可以使这种生活史转变得以进化，所有物种都独立地进化出了相同的解决方案。或者，如果涉及到不同的机制，就会有令人信服的证据表明，在密切相关的物种进化过程中，同样的适应问题的真正独立的解决方案可以而且确实发生了。该研究将引入一种研究关键适应性的新方法，在比较的机制框架内同时处理系统发育和分子观点。它将建立一个案例研究，将生态、生理和遗传层面的因果关系联系起来。这些数据将增加我们对进化过程和生物多样性起源的理解。

9509802 One of the outstanding problems in ecological and evolutionary physiology is understanding the mechanisms by which major new features evolve. In particular, when we see the same adaptation in two or more unrelated species, we may ask the fundamental question "Do those species utilize the same physiological and genetic mechanisms to solve their adaptive problem, or do they use different mechanistic solutions to achieve the same adaptive solution?". An answer to this question is needed if we are to understand how organisms adapt to changing environments. To address this question, this research will use a model group of salamander species from Mexico and the US that have altered their physiological pathway to metamorphosis: some species go through a normal metamorphosis, while others forego metamorphosis and complete their lives as sexually mature, aquatic larval animals. Several strategies, ranging from molecular analyses of the genes responsible for metamorphosis, to administering hormones that regulate metamorphic completion, will be used to determine the mechanism used to achieve this ecologically important life-history shift in six different species of salamander. If the mechanism is the same in all species, this will indicate that there is essentially only one physiological and genetic mechanism by which this life-history shift can evolve, and all species have independently evolved the same solution. Alternatively, if different mechanisms are involved, there will be compelling evidence that truly independent solutions to the same adaptive problem can and do occur during evolution of closely related species. The research will introduce a novel approach for studying key adaptations, where both phylogenetic and molecular perspectives are simultaneously treated within a comparative, mechanistic framework. It will establish a case study linking ecological, physiological, and genetic levels of causation. The data will increase our understanding of the processes of evolution and the origin of biological diversity.