Evolution of interacting populations

15 Sep 2019, 12:30 → 17 Sep 2019, 12:45 Europe/Berlin

Lecture Hall (MPI for Evolutionary Biology, Plön)

Evolution is driven by individual birth and death. These microscopic processes drive the changes in the macroscopic population quantities. However, microscopic processes are not determined by traits of the single individual but rather are determined by interactions between individuals. Hence, studying interactions is crucial to understand the evolution of population properties. Theoretical models increasingly take into account the importance of ecological factors on evolution. In parallel, many experimental results have shown that ecological dynamics affects evolutionary dynamics. Collectively, these findings have shed new light on the ecology and evolution of various populations, including microbiomes, cancer cells, and multicellular organisms. In this workshop, we assemble scientists studying evolving ecological systems from mathematics and physics perspective to discuss the directions that evolution can take and how to model such systems.

The format of the workshop: our workshop is composed of two parts. During the first two days, all speakers give presentations. On the last day, the workshop is concluded with a discussion.

The workshop is organized by Hye-Jin Park and Yuriy Pichugin. 
Confirmed invited speakers are: 
Tobias Galla,
Jeff Gore, 
Silvia De Monte,
Andrew Morozov, 
Wenying Shou,
Kalin Vetsigian.
 

Sunday, 15 September

13:00 → 13:50 Check-In & Snack

13:50 → 14:00 Opening

Speakers: Hye-Jin Park, Yuriy Pichugin

14:00 → 15:40 Session 1

14:00 Stability and Diversity in random Lotka-Volterra systems with non-linear functional response

Speaker: Laura Sidhom

Sidhom.pdf

14:20 Cellular potlatch: The advantage of leakage of essential metabolites and resultant symbiosis of diverse species

Speaker: Jumpei Yamagishi

Yamagishi.pdf

14:40 Stability and diversity in random ecologies: the physicists’ frustration

Nearly 50 years ago Robert May sparked the “diversity-stability debate” in ecology. May’s work centres on the so-called community matrix covering the stability of large ecological communities. Assuming that this matrix has random entries May claims that an increased number of species promotes instability. As a consequence of this work a decade-long debate has ensued, leading to hundreds of papers asserting that increased complexity promotes stability, rather than to make ecosystems unstable. Recently, the debate has resumed in a number of high-profile papers extending May’s work to matrices with more structure than the simple uncorrelated case originally considered in the 1970s.

Much of the theoretical work in this area relies on random matrix theory’. The origins of this theory can be traced back to the work of Wigner in the context of nuclear physics in the 1950’s. Models with random interaction coefficients are also at the heart of the theory of disordered systems, developed to study spin glasses in the 1970s and early 1980s. The key element of these models isfrustration’ — competing forces act on the components of the system, and not all interactions can be satisfied simultaneously. Physicists have been dealing with this frustration for nearly 50 years, and have a number of tools ready to be deployed on the models of random ecologies at the heart of the complexity-stability debate. At the same it is difficult for physicists to acquire sufficient knowledge of the ecology background to make meaningful contributions.

In this talk I will try to summarise the techniques statistical physics can offer, random matrix theory, path integrals and the so-called ‘cavity method’. I will explain what these tools can deliver in the context of simple random replicator and random Lotka-Volterra models. I will also try to state my personal view on what physicists and ecologists can do to ensure that the tools from statistical physics are used to the full in the context of the diversity-stability debate, and in a manner which is valuable and meaningful to ecologists.

Speaker: Tobias Galla

15:40 → 16:10 Coffee

16:10 → 18:10 Session 2

16:10 The nature and prevalence of collective behaviour in ecological communities

Speaker: Jean-Francois Arnoldi

Arnoldi.pdf

16:30 Why is cyclic dominance so rare?

Natural populations contain multiple types of coexisting individuals.
Individuals interact with each other affecting the death and birth of them, and this interaction structure shapes population composition.
Some interaction structures support the coexistence of multiple diverse types, while others favour one the and drive all others to extinction.
A paramount example of structures supporting diversity is a cyclic dominance, illustrated by the rock-paper-scissor game.
This cyclic dominance structure has attracted a lot of attention because multiple types can coexist without direct mutualism.
However, traditional work assumes a predefined set of cyclically dominated types, while the formation of a cyclic dominance from evolution has not been studied well.
We develop the model of an evolving population and study the formation of the cyclic dominances.
Our results show that the cyclic dominances emerge rarer than non-cyclic dominances.
We also address in which circumstance cyclic dominances are enhanced and suppressed.

Speaker: Hye-Jin Park

16:50 Rapid Adaptation and Diversification under Competition for Limiting Resources

Speaker: Massimo Amicone

Amicone.pdf

17:10 Building microbial communities from the bottom up

Speaker: Jeff Gore

Gore.pdf

18:10 → 21:10 Dinner

Monday, 16 September

09:00 → 11:00 Session 3

09:00 Spatial eco-evolutionary feedbacks mediate coexistence in prey-predator systems

Speaker: Eduardo Henrique Colombo

Colombo.pdf

09:20 Emergence of a stable nonequilibrium bacteria-phage collective state from scale-dependent feedback

Speaker: Hong-Yan Shih

Shih.pdf

09:40 Stochastic colonization of microbe-free hosts

Speaker: Roman Zapien

Zapien.pdf

10:00 Towards constructing a mathematically rigorous framework for modelling evolutionary fitness

In modelling biological evolution, a major mathematical challenge consists in an adequate quantification of selective advantages of species. Current approaches to modelling natural section are often based on the idea of maximization of a certain prescribed criterion – evolutionary fitness. This paradigm was inspired by the seminal Darwin’s idea of the ‘survival of the fittest’. However, the concept of evolutionary fitness is still somewhat vague, intuitive and is often subjective. On the other hand, by using different definitions of fitness one can predict conflicting evolutionary outcomes, which is obviously unfortunate. In this talk, I present a novel axiomatic approach to model natural selection in dynamical systems with inheritance in an arbitrary function space. For a generic self-replication system, I introduce a ranking order of inherited units following the underlying measure density dynamics. Using such ranking, it becomes possible to derive a generalized fitness function which maximization will predict long-term evolutionary outcome. The approach justifies the variational principle of determining evolutionarily stable behavioural strategies. I demonstrate a new technique allowing to derive evolutionary fitness for population models with structuring (e.g. in models with time delay) which was so far a mathematical challenge. Finally, I show how the method can be applied to a von Foerster continuous stage population model.

Speaker: Andrew Morozov

11:00 → 11:30 Coffee

11:30 → 13:30 Session 4

11:30 Mutation-selection stationary distribution in structured populations

Speaker: Sedigheh Yagoobi

Yagoobi.pdf

11:50 Eco-Evolutionary Dynamics in a Randomly Switching Environment

Speaker: Mauro Mobilia

Mobilia.pdf

12:10 Coupled demography of two sympatric lizard species

Speaker: Hibraim Perez-Mendoza

Perez-Mendoza.pdf

12:30 Artificial selection of microbial communities

I will discuss our theoretical work on the artificial selection of microbial communities.

Speaker: Wenying Shou

13:30 → 15:00 Lunch

15:00 → 16:40 Session 5

15:00 Directionality and community-level selection

Speaker: Guy Bunin

Bunin.pdf

15:20 Evolution of simple multicellular life cycles

A fascinating wealth of life cycles is observed in biology, from unicellularity to the concerted fragmentation of multicellular units.
However, the understanding of factors driving their evolution is still limited.
Here, we develop a model in which groups arise from the division of single cells that do not separate but stay together until the moment of group fragmentation.
We allow for all possible fragmentation patterns and search for evolutionary stable strategy.
We show that if the population size is constrained by the density-dependent death rate of groups, the population dynamics is equivalent to the model with unconstrained population growth.
Further analysis reveals that fragmentation modes that maximise growth rate comprise a restrictive set of binary fragmentation patterns that include production of unicellular propagules and division into two similar size groups.
All in all, our model provides a framework for exploring the adaptive significance of fragmentation modes and their associated life cycles.

Speaker: Yuriy Pichugin

15:40 Multi-level evolutionary dynamics of nested Darwinian populations and the evolution of collective heredity

Speaker: Silvia De Monte

DeMonte.pdf

16:40 → 18:00 Walk around the Schöhsee

18:00 → 20:00 Dinner

Tuesday, 17 September

09:00 → 10:40 Session 6

09:00 Privatisation of public goods can cause population collapse

Speaker: Richard Lindsay

Lindsay.pdf

09:20 Artificial selection in small bacterial communities

Speaker: Björn Vessman

Vessman.pdf

09:40 Do single season frequency changes predict multi-season outcome for a mixed species Candida community?

Speaker: Alys Jepson

Jepson.pdf

10:00 How invader and community traits shape the long-term consequences of biotic invasions

Speaker: Matthieu Barbier

Barbier.pdf

10:20 Multiple evolutionary (games) interactions

Evolutionary game theory has been successful in describing phenomena from bacterial population dynamics to the evolution of social behaviour. However, it has focused on a single game describing the interactions between individuals. Organisms are simultaneously involved in many intraspecies and interspecies interactions. Therefore, there is a need to move from single games to multiple games. However, these interactions in nature involve many players. Shifting from 2-player games to multiple multiplayer games yield richer dynamics closer to natural settings. Such a complete picture of multiple game dynamics (MGD), where multiple players are involved, was lacking. We show that if the individual games involved have more than two strategies, then the combined dynamics cannot be understood by looking only at individual games. Expected dynamics from single games is no longer valid, and trajectories can possess different limiting behaviour. Our results highlight that studying a set of interactions defined by a single game can be misleading if we do not take the broader setting of the interactions into account. Through our results and analysis, we thus discuss and advocate the development of evolutionary game(s) theory, which will help us disentangle the complexity of multiple interactions.

Speaker: Vandana Revathi Venkateswaran

10:40 → 11:40 Farewell & Snack