Dissertation Research: Expression and Inheritance of a Life History Polymorphism

生命周期，或生命历史路径，是生物体从起源到生命终止或死亡所经历的不同阶段的演替。生命周期可能很简单，就像大多数显眼的动物所表现的那样；鸟类和哺乳动物在孵化或出生时，除了大小和比例外，在大多数方面都与它们的父母相似。然而，大多数动物(昆虫和其他无脊椎动物)有复杂的生命周期，至少有两个截然不同的生命阶段(例如，飞蛾和蝴蝶开始时是无翼的软体毛虫)。绝大多数生物体只有一个生命周期，无论它是简单的还是复杂的。鼹螈(Ambystoma Talpoideum)是这一一般规则的例外。许多个体表现出复杂的生命周期，这在两栖动物中很常见。它们以水生幼虫的形式开始生活，然后经历蜕变(变态)成为陆生成虫。然而，一些个体能够跳过从水生幼虫阶段到陆地成虫阶段的过渡，转而成为水生成虫。虽然众所周知，个体采用其中一种生活史途径的倾向是由遗传和环境因素共同决定的，但这些因素的相对贡献还没有被很好地理解。这项拟议的研究利用实验技术调查了这种生命周期多态的潜在原因。研究结果将根据可供选择的生活史途径的短期(个人)和长期(群体)影响来解释。

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.