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
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Scheduled lectures
Eric Pedersen (Concordia University, Montreal):
How do we define a patch? Deriving subpopulation structure from movement models using random-walk-based distance metrics
3 October, 2023
The metapopulation framework is a cornerstone tool for modelling spatially structured populations. A Metapopulation is defined as a set of subpopulations living in well-mixed patches, connected by inter-patch movement. However, there is currently no clear single definition of what constitutes a “patch” of habitat in fragmented and heterogeneous landscape. In this talk, I argue that we should define patches based on synchronization of population dynamics driven by local interactions between individuals. Further, when interaction is driven by individual patterns of movement and individual movement follows a Markov random walk, I show that it is possible to derive a measure of lifetime encounter probabilities between individuals inhabiting the landscape. This can be used to define a consistent metric for clustering locations on a landscape based on patterns of encounter probability. I demonstrate an eigenvector-decomposition-based approach to approximating this metric for large landscapes, and show how this approach works for clustering simulated landscapes and spatially structured marine habitat of Northern Shrimp in northern Atlantic waters in Canada.
Tanya Rogers (NOAA): Chaos and intermittent instability in ecological systems
17 October, 2023
Chaotic dynamics are thought to be rare in natural populations, but this may be due to methodological and data limitations, rather than the inherent stability of ecosystems. Following extensive simulation testing, we applied multiple chaos detection methods to a global database of 172 population time series and found evidence for chaos in >30%. Chaos prevalence and Lyapunov exponents displayed patterns related to taxonomic group, generation time, and body mass. We then explored how chaotic dynamics and temporal patterns in local instability varied geographically and at different taxonomic resolutions using a compilation of plankton time series from 17 lakes and 4 marine sites. Overall, the results demonstrate that chaos is not rare in natural populations, indicating that there may be intrinsic limits to ecological forecasting and cautioning against the use of steady-state approaches to conservation and management. Our results also suggest that prediction accuracy, sensitivity to change, and management efficacy may be greater at certain times of year and that prediction may be more feasible for taxonomic aggregates.
Elisa Thebault (IEES Paris): Emerging niche clustering results from both competition and predation
7 November, 2023
Understanding species coexistence has been a central question in ecology for decades, and the notion that competing species need to differ in their ecological niche for stable coexistence has dominated. Recent theoretical and empirical work suggests differently. Species can also escape competitive exclusion by being similar, leading to clusters of species with similar traits. This theory has so far only been explored under competition. By combining mathematical and numerical analyses, we reveal that competition and predation are equally capable to promote clusters of similar species in prey–predator communities, their relative importance being modulated by resource availability. We further show that predation has a stabilizing effect on clustering patterns, making the clusters more diverse. Our results merge different ecological theories and bring new light to the emergent neutrality theory by adding the perspective of trophic interactions. These results open new perspectives to the study of trait distributions in ecological interaction networks.
Hanna Kokko (Zürich)
14 November, 2023
Vadim Karatayev (University of Guleph)
28 November, 2023
Shripad Tuljapurkar (Stanford)
23 January, 2024