Life History Models of Symbiosis

大多数生物体体内都有一个细菌、病毒和其他微生物群落。这些微生物被称为共生体。这些共生体中的一些是寄生的，对它们的宿主造成伤害。在其他情况下，寄主依靠它们的共生体提供营养、消化酶和防御其他寄生虫。本研究分析了共生体生活史性状的演化。这些特征包括在宿主内的繁殖率、感染的时间过程（生命周期）、宿主之间的传播方式以及对宿主的危害或益处。宿主控制共生体的潜力也将被分析。例如，一些寄主似乎操纵其共生体繁殖和传播的时间和模式。这种寄主控制可能对共生体从有害伙伴向有益伙伴进化的趋势有很强的影响。本研究发展数学和计算机模型来阐明影响宿主-共生体进化的基本过程。然后将一般模型应用于广泛的特定系统。一个例子是细菌对宿主造成不同程度的伤害（毒力）。第二个例子是传播方式与共生体的生活史之间的关系，共生体有助于它们的昆虫宿主的消化过程。

Frank 9627259 Most organisms have a community of bacteria, viruses and other microorganisms living within their bodies. These microorganisms are called symbionts. Some of these symbionts are parasitic, causing harm to their hosts. In other cases the hosts depend on their symbionts for nutrients, digestive enzymes and defense against other parasites. This study analyzes the evolution of symbiont life history traits. These traits include reproductive rate within the host, the time-course (life-span) of infection, mode of transmission between hosts, and harm or benefit to the host. The host's potential to control their symbionts will also be analyzed. For example, some hosts appear to manipulate the timing and mode of their symbionts' reproduction and transmission. Such host control may have a strong influence on the tendency of symbionts to evolve from harmful to beneficial partners. This research develops mathematical and computer models to clarify the basic processes that influence host-symbiont evolution. The general models are then applied to a wide range of particular systems. One example focuses on the varying degree of harm (virulence) that bacteria cause their hosts. A second example is the relationship between mode of transmission and the life history of symbionts that aid the digestive processes of their insect hosts.