International Initiative for Theoretical Ecology

Ehud Meron (Ben-Gurion): TBA
2021-12-07 09:00 - 10:00 (America/Los_Angeles)
Zoom link: https://liu-se.zoom.us/j/63158449287
Past lectures are on the YouTube channel: https://www.youtube.com/c/TheoreticalEcologySeminarSeries

Jeremy W. Fox (University of Calgary): TBA
2021-11-23 09:00 - 10:00 (America/Los_Angeles)

Robert D. Holt (University of Florida): COVID-19 meets the Hutchinsonian niche
2021-11-09 09:00 - 10:00 (America/Los_Angeles)

Rachel Germain (UBC): Theory in service of empirical research: examples from experiments on the ecology and evolution of species coexistence
2021-10-26 09:00 - 10:00 (America/Los_Angeles)
Science operates through a healthy feedback between theory and experiments. As an empiricist who uses theory for different purposes, I will begin by describing some barriers to more fully integrating theory into empirical research in ecology and evolution (and how to overcome those barriers). I will then describe two applications of theory in my own work: 1. how empirical findings have inspired new questions to be addressed theoretically, and, 2. how ecological theories guide the questions I ask and the experiments I design (and some challenges to doing so). Within this overarching framework, I will focus on several projects, including: how spatial scale has counter intuitive effects on the evolution of life history strategies, how species coexistence evolves on microevolutionary and macroevolutionary timescales, and how coexistence theory can provide insights for speciation.

Laura Dee (Colorado Boulder): Putting ecological theory to work for conservation
2021-10-12 09:00 - 10:00 (America/Los_Angeles)
Abstract. Two grand challenges of our time are climate change and biodiversity loss. This talk focuses on the fundamental question of: to what extent can ecological theory help us understand the consequences of these global changes to inform conservation? I will present two examples investigating this larger question: 1) the consequences of extreme events in boreal forests for ecological stability versus ecosystem services outcomes’ and the 2) vulnerability of food webs versus ecosystem services to species losses in coastal food webs. In the first case, commonly used ecological measures also fall short of predicting disturbance impacts on forest ecosystem services– exhibiting low correlations or systematic biases. In the other case, food web robustness is strongly related to ecosystem service robustness in aggregate, but different types of ecosystem services vary dramatically in their robustness to species’ losses. Together, this work highlights that the complex nature of socioeconomic and ecological systems create challenges for extrapolating ecological theory to understand threats from global change for conservation goals . Thus, I will highlight exciting research avenues for discussion on how ecological theory to contribute to conservation and interdisciplinary research in our inherently socio-environmental systems.

Mathew Leibold (University of Florida): Linking process to pattern in community assembly in diverse metacommunities
2021-09-28 09:00 - 10:00 (America/Los_Angeles)
Abstract:
I’m interested in exploring the degree to which theory on ‘disordered systems’ to community assembly can be linked to statistical methods of pattern analysis. Here, I hope to describe the problem and outline some possible approaches and answers. By doing so, I hope to generate interest and discussion on possible solutions.
Zoom link: https://liu-se.zoom.us/j/63158449287
Past lectures are on the YouTube channel: https://www.youtube.com/c/TheoreticalEcologySeminarSeries

Jacob D. O’Sullivan (Queen Mary): The emergent macroecology of Lotka-Volterra metacommunities
2021-09-14 09:00 - 10:00 (America/Los_Angeles)
Abstract:
For decades Lotka-Volterra community models have been used to try to understand how ecological interactions may drive community-scale properties such as species richness, network structure, and species abundance distributions; in short the various dimensions of biodiversity. Here I show how extending the basic community models into spatially and environmentally heterogeneous landscapes can help us understand how local scale ecological processes – abiotic and biotic filtering, and dispersal – can propagate up the organisational hierarchy to determine regional scale patterns in biodiversity.
Zoom link: https://liu-se.zoom.us/j/63158449287
Past lectures are on the YouTube channel: https://www.youtube.com/c/TheoreticalEcologySeminarSeries

Rafael D'Andrea (Stony Brook University): Counting niches: Can spatial patterns reveal niche partitioning in tropical forests?
2021-06-29 09:00 - 10:00 (America/Los_Angeles)
Abstract:
We investigate the idea that tropical biodiversity is maintained by a combination of niche segregation and niche sharing among species by asking whether tree species in Barro Colorado Island, Panama, fall into groups differing by the local conditions where they typically occur. We first group together species often found near each other, then show that the resulting three groups are statistically associated with distinct local nutrient levels. Finally, we find clear distinctions among those groups in traits associated with life history strategies.
Zoom link: https://liu-se.zoom.us/j/63158449287
Past lectures are on the YouTube channel: https://www.youtube.com/c/TheoreticalEcologySeminarSeries
eventbrite link (for reminders): https://www.eventbrite.co.uk/e/theoretical-ecology-seminar-series-tickets-119884512805

Neo Martinez (Indiana University): Predicting Ecosystem Phenotype from Community Genotype: Can Allometric Trophic Network Theory Help Meet the Challenge?
2021-06-15 09:00 - 10:00 (America/Los_Angeles)
Abstract:
Theoretical ecology has investigated a series of concepts from stability and complexity through biodiversity and ecosystem function to coexistence and tipping points for which empirical data typically plays a less-than-satisfying role. To coax theoretical ecology towards increased empirical relevance and broader scientific synthesis, I propose that environmental biologists focus on predicting key characteristics of an ecosystem from the genotypes within its constituent communities. Such metagenomes effectively identify the organisms and their interactions within ecosystems. Following the first of several “virtual cells” built by systems biologists that predicts a human pathogen’s phenotype from its genotype, powerful social (e.g., structured collaborations), scientific (e.g., networks of networks) and technical (e.g., computer and data science) concepts for accomplishing the proposed task will be described along with a plausible workflow based on allometric trophic network theory. Anticipated benefits include more integrated, mechanistic, and predictive theory of how ecosystem structure and function emerge from organisms interacting within a habitat.
Zoom link: https://liu-se.zoom.us/j/63158449287
Past lectures are on the YouTube channel: https://www.youtube.com/c/TheoreticalEcologySeminarSeries
eventbrite link (for reminders): https://www.eventbrite.co.uk/e/theoretical-ecology-seminar-series-tickets-119884512805

Chuliang Song (McGill University): An environment-dependent framework to study ecological networks
2021-06-01 09:00 - 10:00 (America/Los_Angeles)
Abstract: Ecological networks—how species interactions are organized within ecological communities—are highly structured, which has motivated generations of ecologists to elucidate how these structures affect species coexistence. Unfortunately, we still do not have a clear and consistent answer about the link between network structure and species coexistence. A possible explanation is that most of the studies do not take into account that the environment affects both network structure and species coexistence due to the multidimensional and changing nature of environmental factors. In this context, the structural stability approach provides a theoretical framework grounded on biological realism to quantitatively link network structure, species coexistence, and environmental factors. In this talk, I will introduce the theoretical framework and computational tools of the structural stability approach, and present the empirical validation using field and experimental observations.
The Zoom link is the usual: https://liu-se.zoom.us/j/63158449287

Cinzia Soresina (University of Graz): The influence of cross-diffusion in pattern formation: multistability and Hopf bifurcations
2021-05-18 09:00 - 10:00 (America/Los_Angeles)
Abstract
The Shigesada-Kawasaki-Teramoto model (SKT) was proposed to account for stable inhomogeneous steady states exhibiting spatial segregation, which describes a situation of coexistence of two competing species. Even though the reaction part does not present the activator-inhibitor structure, the cross-diffusion terms are the key ingredient for the appearance of spatial patterns. We provide a deeper understanding of the conditions required on both the cross-diffusion and the reaction coefficients for non-homogeneous steady states to exist, by combining a detailed linearised and weakly non-linear analysis with advanced numerical bifurcation methods via the continuation software pde2path. In particular, we study the role of the additional cross-diffusion term in pattern formation, showing that the bifurcation diagram undergoes major deformations leading to multistability regions. The presence of time-periodic spatial pattern appearing via Hopf bifurcation points is also investigated.
Zoom link: https://liu-se.zoom.us/j/63158449287
Past lectures are on the YouTube channel: https://www.youtube.com/c/TheoreticalEcologySeminarSeries
eventbrite link (for reminders): https://www.eventbrite.co.uk/e/theoretical-ecology-seminar-series-tickets-119884512805

Masato Yamamichi (The University of Queensland): How does rapid evolution promote species coexistence?
2021-05-04 06:00 - 07:00 (America/Los_Angeles)
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 ecological dynamics. Here, I show how rapid evolution can promote species coexistence via density-dependent sexual and social selection (intraspecific adaptation load: Yamamichi et al. 2020 Trends Ecol. Evol.) and resource-dependent adaptive foraging in limit cycles (relative nonlinearity: Yamamichi & Letten 2021 Ecol. Lett.). Then I will discuss the potential synthesis of theories on species coexistence and eco-evolutionary dynamics.
Zoom link: https://liu-se.zoom.us/j/63158449287
Past lectures are on the YouTube channel: https://www.youtube.com/c/TheoreticalEcologySeminarSeries
eventbrite link (for reminders): https://www.eventbrite.co.uk/e/theoretical-ecology-seminar-series-tickets-119884512805

Priyanga Amarasekare (UCLA): Predicting the effects of climate warming: from chemistry to evolution
2021-04-20 09:00 - 10:00 (America/Los_Angeles)
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 to life on earth. Predicting the effects of warming requires knowing whether organisms have sufficient plasticity to respond to current levels of warming, and whether plasticity can evolve fast enough to keep pace with warming. But, existing plasticity is the result of past evolution, while future plasticity is the result future evolution. My thesis is that chemistry is integral to both understanding past evolution and predicting future evolution. I will present theory and data to support this idea and discuss future research directions.
Zoom link: https://liu-se.zoom.us/j/63158449287
Past lectures are on the YouTube channel: https://www.youtube.com/c/TheoreticalEcologySeminarSeries
eventbrite link (for reminders): https://www.eventbrite.co.uk/e/theoretical-ecology-seminar-series-tickets-119884512805

György Barabás (Linköping): Coexistence and parameter sensitivity in stationary aperiodic environments
2021-04-06 09:00 - 10:00 (America/Los_Angeles)
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 for understanding coexistence in variable environments.
Zoom link: https://liu-se.zoom.us/j/63158449287
Past lectures are on the YouTube channel: https://www.youtube.com/c/TheoreticalEcologySeminarSeries
eventbrite link (for reminders): https://www.eventbrite.co.uk/e/theoretical-ecology-seminar-series-tickets-119884512805

Theresa Ong (Dartmouth College): Complex hysteretic patterns: hidden loops and ecological traps
2021-03-23 09:00 - 10:00 (America/Los_Angeles)
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 ecology. Here, I focus on the irreversibility of these transitions, formally known as hysteresis. I will discuss a variety of complicated hysteretic patterns derived from theory and experiments, which include “unattainable” stable states that once lost may never be recovered.
Zoom link: https://liu-se.zoom.us/j/63158449287
Past lectures are on the YouTube channel: https://www.youtube.com/c/TheoreticalEcologySeminarSeries
eventbrite link (for reminders): https://www.eventbrite.co.uk/e/theoretical-ecology-seminar-series-tickets-119884512805

Géza Meszéna (Eötvös University): Coexistence, niche, adaptation and all that...
2021-03-09 09:00 - 10:00 (America/Los_Angeles)
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 reach to the phenomenal complexity of the ecosystems.
Zoom link: https://liu-se.zoom.us/j/63158449287
Past lectures are on the YouTube channel: https://www.youtube.com/c/TheoreticalEcologySeminarSeries
eventbrite link (for reminders): https://www.eventbrite.co.uk/e/theoretical-ecology-seminar-series-tickets-119884512805

James O'Dwyer (University of Illinois): Cooperation, Resource Exchange, and Stability
2021-02-23 09:00 - 10:00 (America/Vancouver)
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 model the consumption and exchange of resources explicitly, and show that these processes imply new results and principles for the stability of ecological communities.
Zoom link: https://liu-se.zoom.us/j/63158449287
Past lectures are on the YouTube channel: https://www.youtube.com/c/TheoreticalEcologySeminarSeries
eventbrite link (for reminders): https://www.eventbrite.co.uk/e/theoretical-ecology-seminar-series-tickets-119884512805

Thomas Koffel (Michigan State): A niche theory of positive interactions
2021-02-09 09:00 - 10:00 (America/Los_Angeles)
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 of theoretical examples.
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
2021-01-26 09:00 - 10:00 (America/Los_Angeles)
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 stochasticity, in finite populations of discrete individuals. Today we add one more complication: spatial structure and local movement, so that invader populations are clumped, and locally common even when globally rare.
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

Camille Carpentier (University of Namur): A new link-species relationship connects ecosystem structure and stability
2021-01-12 09:00 - 10:00 (America/Los_Angeles)
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

Nadav Shnerb (Bar-Ilan University): Quantifying coexistence
2020-12-08 09:00 - 10:00 (America/Los_Angeles)
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 an alternative framework and introduce a new metric for invasibility under both demographic and environmental stochasticity.
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

Stefano Allesina (University of Chicago): A metapopulation model in which patches have memory
2020-11-24 09:00 - 10:00 (America/Los_Angeles)
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 (for reminders): https://www.eventbrite.co.uk/e/theoretical-ecology-seminar-series-tickets-119884512805

Sebastian Schreiber (UC Davis): Towards a general theory of coexistence: Lyapunov exponents, auxiliary variables, and Hofbauer's criterion
2020-11-09 09:00 - 10:00 (America/Los_Angeles)
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). Originally developed for deterministic models without population structure, Hofbauer’s criterion has been extended in the past decade to models allowing for auxiliary variables and environmental stochasticity. In this talk, I review the key ingredients of this theory and illustrate its use in multi-species models with intransitivities, eco-evolutionary feedbacks, sexual dimorphisms, autocorrelated environmental fluctuations, or spatial structure.
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

André M. de Roos (University of Amsterdam): Dynamics of within-population structure stabilise complex ecological communities
2020-10-27 09:00 - 10:00 (America/Los_Angeles)
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 depends on substantial self-limitation of species. Using a stage-structured food web model I show that differences between juveniles and adults result in diverse ecological communities that are stable or exhibit limited-amplitude fluctuations, despite that only a single basal species is self-regulated. Eigenvalue analysis reveals that community stability results from dynamic changes in within-population stage-structure that override destabilising effects induced by the species interaction network.
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

Vadim Karatayev (University of Guelph): Species heterogeneity can reduce the potential for alternative stable states in food webs
2020-10-13 17:00 - 18:00 (Europe/London)
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 by either consumer or resource guilds can arise when consumer species improve conditions in the same way, for instance when different herbivore species promote habitat-forming corals by limiting the total cover of macroalgae. Conversely, specialized feedbacks where size refugia or group defense make individual resource species inedible are less likely to drive many-species alternative stable states because losing the most vulnerable consumers cascades into a guild-wide collapse.
Vadim Karatayev, Marissa Baskett, Egbert van Nes, Marten Scheffer
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
Video: https://www.youtube.com/watch?v=2bZfsRBXJX4

Éva Kisdi (University of Helsinki): The evolution of habitat choice facilitates niche expansion
2020-09-29 17:00 - 18:00 (Europe/London)
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 local adaptation, we find the evolutionarily stable habitat choice as a function linking the probability of settlement to the local environment. When the local adaptation trait co-evolves, the metapopulation can become polymorphic. Our main result shows that coexisting strains with only slightly different local adaptation traits evolve substantially different habitat choice. In turn, different habitat use selects for divergent local adaptations. We thus propose that under wide conditions, the joint evolution of habitat choice and local adaptation can facilitate niche expansion via diversification.
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
Video: https://www.youtube.com/watch?v=qMpR1mNLkq4&t=293s

Guy Bunin: Phase-transitions as signatures of complex communities
2020-09-15 17:00 - 18:00 (Europe/London)
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 how they differ from related low-dimensional behavior.
Video: https://www.youtube.com/watch?v=Dw3Gsa8FI18
