Date/Time Date(s) - 23/01/20252:30 pm - 3:30 pm
Speaker: Dr. Rebecca Tyson (UBC – Okanagan)
Location: Hamilton Hall, Room 410 / Zoom
Title: Phase-sensitive tipping in ecosystems: A new mechanism for extinction
Abstract: Cyclic systems can exhibit highly unexpected behaviour when subject to external forcing. Many resource-consumer systems are inherently cyclic, and subject to climatic forcing that can also be dominated by certain frequencies. This coupling between two cyclic systems could mean that the observed resource-consumer dynamics may be more dependent on the characteristics of the climatic time series than is generally suspected. In particular, we ask if the predicted changes to the colour and frequency of environmental noise could put cyclic resource-consumer systems at risk. We investigate this question by studying a continuous predator-prey model and a discrete host-parasitoid model, both with an Allee effect, under climatic forcing modeled via changes in prey or host productivity.
Our analysis of these models uncovers a counterintuitive behaviour, which we call phase tipping or P-tipping, where tipping to extinction does occur under climate variability, but only from certain phases of the resource-consumer cycle, and only when there is a sudden drop in productivity. This tipping occurs even if the resource-consumer cycle exists and is stable for all values of the climate parameters. Intuitively, P-tipping arises because a fixed drop in prey resources has distinctively different effects when applied during the phases of the oscillations with the fastest growth and the fastest decline of resource.