Dissertation Research: Expression and Inheritance of a Life History Polymorphism

Semlitsch 9801458生命周期或生命史途径是生物体从起源到死亡所经历的不同阶段的连续。生命周期可能很简单，就像那些最引人注目的动物一样;鸟类和哺乳动物在孵化或出生时，除了大小和比例外，在大多数方面都与父母相似。然而，大多数动物（昆虫和其他无脊椎动物）都有复杂的生命周期，其中至少有两个完全不同的生命阶段（例如，飞蛾和蝴蝶开始的生命是无翼的软体毛虫）。绝大多数生物都有一个单一的生命周期，无论是简单的还是复杂的。鼹鼠蝾螈（Ambystoma talpoideum）是这个一般规则的例外。许多个体表现出复杂的生命周期，这在两栖动物中很常见。它们开始生活为水生幼虫，然后经历转变（变态）成为陆地成虫。然而，有些个体能够跳过从水生幼虫阶段到陆生成虫阶段的过渡，而是成为水生成虫。虽然人们知道，一个人采用这些生活史途径中的一个或另一个的倾向是由遗传和环境因素的组合决定的，但这些因素的相对贡献还没有得到很好的理解。拟议的研究调查的根本原因，这种生命周期多态性使用实验技术。结果将根据替代生活史途径的短期（个体）和长期（群体）影响进行解释。

Semlitsch9801458A life cycle, or a life history pathway, is the succession of distinct stages an organism passes through from its origin to its expiration or death. Life cycles may be simple, like those exhibited by most conspicuous animals; birds and mammals that at hatching or birth, resemble their parents in most regards save for size and proportion. However, most animals (insects and other invertebrates) have complex life cycles, where there are at least two radically different phases of life (for example, moths and butterflies that begin life as wingless, soft-bodied caterpillars). The overwhelming majority of organisms have a single life cycle, be it simple or complex. The mole salamander (Ambystoma talpoideum) is an exception to this general rule. Many individuals exhibit complex life cycles, which is common among amphibians. They begin life as aquatic larvae then undergo a transformation (metamorphosis) to become terrestrial adults. Some individuals, however, are able to skip the transition from the aquatic larval stage to the terrestrial adult stage and instead become aquatic adults. Although it is known that the propensity for an individual to adopt one or the other of these life history pathways is determined by a combination of genetic and environmental factors, the relative contribution of these is not well understood. The proposed research investigates the underlying causes of this life cycle polymorphism using experimental techniques. The results will be interpreted in light of both the short-term (individual) and long-term (population) effects of alternative life history pathways.