Date/Time
Date(s) - 24/01/2024
10:30 am - 11:30 am

Location: HH 312

Speaker: Chris Greyson-Gaito

Title: Resilience Across Complex Systems in a Variable World

Abstract: With human-caused changes to the world, disturbances are likely to increase. Understanding how our systems, both biological and social, will react and persist in the face of disturbances is, consequently, critical. The concept of resilience addresses how systems maintain structure and function in response to disturbances. Notably, most resilience research addresses how systems maintain structure and function in the face of single disturbances. Recent research is beginning to examine resilience in response to multiple discrete deterministic or stochastic disturbances. Yet, we know that alongside an increasing frequency of disturbances, variability will similarly increase. Considering this future increase in variability, incorporating variability into resilience research is a useful direction. One important aspect within resilience research is how shocks or variability are either amplified or muted, where amplification can be detrimental or useful depending on the system. Amplification or muting of variability can occur via non-linear mechanisms which I define as mechanisms that produce non-linear dynamics. In this dissertation, I examine the non-linear mechanisms of ratchet effects, positive feedbacks, time delays, and network restructuring. I use mathematical modeling to explore how each non-linear mechanism amplifies variability added to different systems. For the ratchet effect mechanism, I examine consumer-resource interactions with stochastic perturbations added to the consumer. Resilience in the consumer-resource interaction is the persistence of the consumer-resource interaction. For the positive feedbacks and time delays mechanisms, I examine crop farm systems with environmental noise added to the production of crop yield. Resilience, here, is the persistence of crop farms. For the network restructuring mechanism, I examine bacteria-bacteriophage interactions in the gut system with environmental variability changing the selection of a gene that can be horizontally transferred through conjugation or transduction via bacteriophage. Resilience is the gut function stability, where variability is, in fact, useful. Overall through examining multiple systems, I illuminate how flexibility and trade-offs are key to resilience in the face of variability.