https://secure-purdue-edu.zoom.us/j/93293105845?pwd=wuaLwBr77JFJNFNiVZrKMKeXbIqvdJ.1
Meeting ID: 932 9310 5845
Passcode: 866973
Title: Noise and determinism across systems: insights from Trinidadian guppies and Soay sheep
Natural populations are nonlinear and exhibit substantial variability. Such variability can shift equilibria, amplify fluctuations, or in some cases push populations toward collapse. A central question is to examine how stochasticity interacts with and alters population dynamics. A related question is whether fluctuations arise primarily from intrinsic density regulation or extrinsic environmental variation. We address these using long-term time series of Trinidadian guppies and Soay sheep. In this talk, I will first discuss the results for guppy dynamics and show their populations follow a stochastic logistic equation, with multiplicative environmental noise. We examine the dynamics of fluctuations using local stability analysis and develop stochastic bifurcation theory to show how fluctuations can alter equilibrium structure. These diagnostics let us rank streams by proximity to a noise-driven regime shift, offering new insights that are likely to be missed by conventional Early Warning Signal metrics. Finally, using spectral analysis we separate intrinsic fluctuations from external periodicities, revealing how populations filter environmental variability into their characteristic dynamics. In the second part of the talk, I will discuss results from Soay sheep population and show how variability in the form of density-dependence alters demographic distributions, life-history trade-offs and lifetime reproductive success. I will end with formalizing the effect of perturbations on vital rates in matrix population models. Together, these results show that stochasticity is not merely added noise but alters resilience and vulnerability by reshaping stability landscapes and life-history structure.
The Midwest Mathematical Biology Seminar will be a series of virtual talks on mathematical biology featuring speakers from the Midwest region and beyond. All areas of mathematical biology will be represented in the seminar series, and a goal for this seminar is to build connections and foster research collaborations.
More information - https://sites.google.com/view/midwest-mathbio-seminar/home
Tiffany Leighton
Email