Loss of Stability and Resilience Before a Tipping Point Leading to Population CollapseWhen: Tuesday, April 23, 2013 at 3:00 pm
Where: DA 5th fl
Speaker: Lei Dai
Organization: PhD Student, GORElaboratory, Department of Physics, Massachusetts Institute of Technology
Tipping points marking population collapse and other critical transitions in natural systems can be described by a fold bifurcation in the dynamics of the system. Theory predicts that the approach of bifurcations will result in an increasingly slow recovery from small perturbations, a phenomenon called critical slowing down [1,2]. We demonstrate the direct observation of critical slowing down before population collapse using replicate laboratorypopulations of the budding yeast Saccharomyces cerevisiae. We mapped the bifurcation diagram experimentally and found a significant increase in both the size and timescale of the fluctuations of population density near a fold bifurcation, in agreement with the theory . Furthermore, we connected yeast populations spatially to evaluate warning signals based on spatio-temporal fluctuations and to identify a novel warning indicator in space: recovery length . As the spatial counterpart of recovery time, recovery length is the distance necessary for connected populations to recover from perturbations in space. Currently we are exploring the correlation between stability and resilience and its implications for the performance of early warning signals in deteriorating environments.