Watch recorded past seminars on our YouTube channel:
https://www.youtube.com/channel/UCLMcVHn2ZuvzhLOGqPczFMg

Guy Bunin: Phase-transitions as signatures of complex communities

Abstract: What characterizes species-rich communities with complex species interactions--for example, competing over many niches? Models predict sharp transitions, as conditions are changed, between qualitatively different dynamical behaviors. These include the abrupt appearance of a vast number of alternative steady-states; and the onset of persistent abundance fluctuations, nearly uncorrelated between species. We discuss these phenomena, and …

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Éva Kisdi (University of Helsinki): The evolution of habitat choice facilitates niche expansion

Abstract: Matching habitat choice and local adaptation are two key factors that control the distribution and diversification of species. We study their joint evolution in a structured metapopulation model with a continuous distribution of habitats. Habitat choice follows from dispersal with non-random immigration, a process always acknowledged yet rarely incorporated into theoretical models. For fixed …

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Vadim Karatayev (University of Guelph): Species heterogeneity can reduce the potential for alternative stable states in food webs

Abstract. Can alternative stable states arise when food webs dissipate feedbacks across many species in diverse systems like coral reefs? Although consumer loss often characterizes degraded ecological states, food web resilience theory predominantly focuses on specific systems and few-species models. After developing a generalized model of consumer collapse, we show that alternative stable states dominated …

Vadim Karatayev (University of Guelph): Species heterogeneity can reduce the potential for alternative stable states in food webs Read More »

André M. de Roos (University of Amsterdam): Dynamics of within-population structure stabilise complex ecological communities

Warning! During this week the time difference between America and Europe is one hour less, than usual. The seminar will begin at 9 am Pacific, as always, but now it will correspond to 4 pm in London and 5 pm in Paris. Abstract: Dynamic models of ecological communities that neglect within-population structure predict that stability …

André M. de Roos (University of Amsterdam): Dynamics of within-population structure stabilise complex ecological communities Read More »

Sebastian Schreiber (UC Davis): Towards a general theory of coexistence: Lyapunov exponents, auxiliary variables, and Hofbauer’s criterion

Warning: this is a Monday! Abstract: In the 1980s, Josef Hofbauer introduced a criterion for mathematically verifying coexistence using per-capita growth rates of species when rare i.e. Lyapunov exponents. This criterion ensures coexistence is robust to large perturbations of the community state (i.e. permanence) and small structural perturbations of the governing equations (i.e. robust permanence). …

Sebastian Schreiber (UC Davis): Towards a general theory of coexistence: Lyapunov exponents, auxiliary variables, and Hofbauer’s criterion Read More »

Stefano Allesina (University of Chicago): A metapopulation model in which patches have memory

Levins' metapopulation model has been extended in numerous ways. Here we analyze a model in which species have distinct colonization rates that depend on which species previously occupied the patch. We connect this model to the Janzen-Connell hypothesis and show some surprising behavior for a simplified version of the model. Zoom link: https://liu-se.zoom.us/j/63158449287 eventbrite link …

Stefano Allesina (University of Chicago): A metapopulation model in which patches have memory Read More »

Nadav Shnerb (Bar-Ilan University): Quantifying coexistence

Abstract. Modern coexistence theory employs mutual invasibility as a coexistence criterion and mean growth rate when rare as an invasibility criterion. When implemented as quantitative metrics, both criteria have shortcomings: persistence time may decline when the chance of invasion grows, and invasibility may decrease as the mean growth rate increases in magnitude. I will discuss …

Nadav Shnerb (Bar-Ilan University): Quantifying coexistence Read More »

Camille Carpentier (University of Namur): A new link-species relationship connects ecosystem structure and stability

Abstract: How does an ecosystem's structure determine its capacity to cope with species removal and perturbations of species densities? To answer this question, we develop a network-specific approach to the link-species relationship, and demonstrate that it formally predicts a robustness-resilience trade-off, both theoretically and in empirical networks. Zoom link: https://liu-se.zoom.us/j/63158449287 eventbrite link (for reminders): https://www.eventbrite.co.uk/e/theoretical-ecology-seminar-series-tickets-119884512805

Stephen Ellner (Cornell): An invitation to spatial coexistence theory

Stephen Ellner (Cornell), Peter Adler (Utah State), Giles Hooker (Cornell), Robin Snyder (Case Western): An invitation to spatial coexistence theory. Abstract: Previously in this series Sebastian Schreiber reviewed stochastic coexistence theory for infinite population models, based on long-term population growth rates of (infinitesimally) rare invaders. Nadav Shnerb presented progress on the challenges posed by demographic …

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Thomas Koffel (Michigan State): A niche theory of positive interactions

Abstract: Niche Theory has traditionally focused on competitive interactions. In this talk, we propose a general framework that expands the theory to positive interactions, such as facilitation and mutualism, using angular metrics of niche difference. We develop novel niche concepts such as the Allee niche and niche expansion, and illustrate them using a diverse set …

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James O’Dwyer (University of Illinois): Cooperation, Resource Exchange, and Stability

Abstract: Models of microbial interactions have been developed in recent years, drawing from taxonomic abundances via amplicon sequencing. Many of these models assume that dynamics through time are primarily driven by pairwise interactions between taxa, but with the drawback that how these interaction strengths may change with environmental context is less than clear. Here we …

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Géza Meszéna (Eötvös University): Coexistence, niche, adaptation and all that…

Abstract: Why are there so many animals? According an old idea, it is because there are so many different possibilities for life to adapt to. I’ll argue that it is still true, and truer than the suggested alternatives. The challenge is to establish the precise mathematical treatment at this level of generality without losing the …

Géza Meszéna (Eötvös University): Coexistence, niche, adaptation and all that… Read More »

Theresa Ong (Dartmouth College): Complex hysteretic patterns: hidden loops and ecological traps

NOTE: Because of the asynchronous transition to Summer Time, the usual time of the seminar (9 a.m. Pacific) is one hour earlier in Europe: 4 p.m. London and 5 p.m. Paris. Abstract: Critical transitions whereby small changes in conditions can cause large and irreversible changes in ecosystem states are a cause of increasing concern in …

Theresa Ong (Dartmouth College): Complex hysteretic patterns: hidden loops and ecological traps Read More »

György Barabás (Linköping): Coexistence and parameter sensitivity in stationary aperiodic environments

Abstract: First, I present a method for calculating how average population densities respond to parameter perturbations when the dynamics are periodic, and show that this practical problem holds a strong connection with basic questions of coexistence. I then generalize this result to stationary nonperiodic density fluctuations. I finish by discussing the connection with existing formalisms …

György Barabás (Linköping): Coexistence and parameter sensitivity in stationary aperiodic environments Read More »

Priyanga Amarasekare (UCLA): Predicting the effects of climate warming: from chemistry to evolution

Abstract I want to make the argument that understanding life on earth requires developing theory that integrates across levels of information, from chemistry to evolution. I am going to focus on temperature variation and phenotypic plasticity, not least because temperature is integral to all life processes, and climate warming poses one of the greatest threats …

Priyanga Amarasekare (UCLA): Predicting the effects of climate warming: from chemistry to evolution Read More »

Masato Yamamichi (The University of Queensland): How does rapid evolution promote species coexistence?

Note: The event takes place 3 hours earlier than usual, because of the location of our lecturer. He will speak at midnight, local time, even in this way. Abstract: Previous studies have revealed that microevolution (i.e., temporal changes in allele frequencies) is pervasive in the wild and may be an important factor for understanding various …

Masato Yamamichi (The University of Queensland): How does rapid evolution promote species coexistence? Read More »

Watch recorded past seminars on our YouTube channel:
https://www.youtube.com/channel/UCLMcVHn2ZuvzhLOGqPczFMg