演讲人: Prof. James Watmough, University of New Brunswick

讲座时间: 5月13日（周二）下午4:00-5:00

讲座地点: 信息楼二层会议室

讲座内容:

Abstract:

Many important questions in ecology and immunology involve dynamical systems with multiple stable states. This presentation covers models for three such systems. The first example involves a feminizing microsporidian parasite thought to be responsible for collapses of mudshrimp populations in the Bay of Fundy. The parasite is transmitted vertically, from mother to child, and influences the size and sex-ratio of the brood. In many immune-system models, treatment works by lowering the reproduction number of the pathogen below a threshold. However, in these models, the pathogen reestablishes itself if the treatment is stopped. In the second part of this talk we present a simple example of a model where treatment can be stopped without reemergence of the pathogen: a situation referred to as sustained-immunity. This is possible because a stable infection-equilibrium coexists with a stable infection-free or low-infection state. Treatment, if applied for a sufficient time, can move the system into the basin of attraction for the infection-free equilibrium, and immunity is sustained after treatment is stopped. The final part of this talk examines a system with an intra-guild predator. These systems can be viewed as coupling two predator prey systems. The two predators and the resource can coexist in equilibrium, in periodic solutions, and in chaotic solutions.