We operate an international seminar series on Theoretical Ecology via Zoom since September, 2020. With some exceptions, the hour-long events are held on every other Tuesday at 9 a.m. Pacific Time, which corresponds to 5 p.m. in London and 6 p.m. in Paris most of the time. Our invited lecturer speaks for cc. 20-30 minutes. The rest of the hour is for questions and discussions, which are often lively. The seminars are recorded and posted on our YouTube channel. We send out notifications before each lecture via email and Twitter. The webinar is organised by György Barabás (dysordys@gmail.com), Géza Meszéna (meszena.geza@ttk.elte.hu) and Chris Terry (christopher.terry@biology.ox.ac.uk). Any comment, or suggestion are welcome.
Zoom link (unless stated otherwise): https://liu-se.zoom.us/j/63158449287
YouTube channel with the lecture videos and teaching material, etc.
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Scheduled lectures
Harman Jaggi (Princeton): Noise and determinism across systems: insights from Trinidadian guppies and Soay sheep
12 May, 2026
Natural populations are nonlinear and exhibit substantial variability. A central question is to examine how variability interacts with and alters population dynamics. We address these using long-term time series of Trinidadian guppies and Soay sheep. In this talk, I will first discuss results for guppies and implications for equilibrium structure, recovery dynamics and vulnerability to perturbations. Using stochastic bifurcation theory, we show how fluctuations can alter equilibrium structure, allowing us to rank streams by proximity to a noise-driven regime shift. Analyses of recovery and spectral structure further reveal how intrinsic dynamics interact with seasonal variation, thereby filtering environmental variability into their characteristic dynamics. Next, using Soay sheep time series, I will discuss demographic mechanisms by which variation in population density can alter 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, our results emphasize stochasticity is not just added noise but alters population resilience and vulnerability by changing stability landscape and life-history structure.