Fixation probabilities in network structured meta-populations

Yagoobi, Sedigheh; Traulsen, Arne

doi:10.1101/2021.07.21.453198

Cited by 3 publications

(8 citation statements)

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“…Studying the effect of spatial structure on early adaptation in rugged fitness landscapes is an interesting topic for future work. Indeed, complex spatial structures with asymmetric updates or migrations impact the probabilities of fixation of mutations [61][62][63][64][65], which should affect early adaptation. Beyond the weak mutation regime, fitness valley crossing by tunneling can aid adaptation [56,57], which may especially impact subdivided populations, as first discussed in Wright's shifting balance theory [1,66] and shown in a minimal model [67].…”

Section: Discussionmentioning

confidence: 99%

Impact of population size on early adaptation in rugged fitness landscapes

Servajean

Bitbol

2022

Preprint

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Due to stochastic fluctuations arising from finite population size, known as genetic drift, the ability of a population to explore a rugged fitness landscape depends on its size. In the weak mutation regime, while the mean steady-state fitness increases with population size, we find that the height of the first fitness peak encountered when starting from a random genotype displays various behaviors versus population size, even among small and simple rugged landscapes. We show that the accessibility of the different fitness peaks is key to determining whether this height overall increases or decreases with population size. Furthermore, there is often a finite population size that maximizes the height of the first fitness peak encountered when starting from a random genotype. This holds across various classes of model rugged landscapes with sparse peaks, and in some experimental and experimentally-inspired ones. Thus, early adaptation in rugged fitness landscapes can be more efficient and predictable for relatively small population sizes than in the large-size limit.

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Section: Discussionmentioning

confidence: 99%

Impact of population size on early adaptation in rugged fitness landscapes

Servajean

Bitbol

2022

Preprint

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“…Equality holds for a well-mixed population which includes self-loops meaning that every individual can also replace itself. In a fully connected graph of subpopulations, where the migration rate is symmetric, and the population is homogeneously distributed among the subpopulations, the fixation probability of the update mechanisms such as MBBdd that reduce to update mechanisms in a graph of individuals is the same as the fixation probability of the equivalent well-mixed population under update mechanism Bd [10].…”

Section: Discussionmentioning

confidence: 99%

“…However, there is an occasional migration to and from other geographical areas. In [10], it has been shown that for a particular update mechanism, the results of evolutionary graph theory [1] do not carry over into graphs of subpopulations. For example, a star-structured metapopulation does not always amplify selection — in some migration regimes, it suppresses selection.…”

Section: Categorising Update Mechanisms For Graphs Of Subpopulationsmentioning

confidence: 99%

“…So far, only a few of these mechanisms have been studied in detail. For example, MBBdd is adopted in [9, 10, 43]. Not all of the observations made in graphs of individuals with the Bd update rule carry over to a graph of subpopulations when the update rule is MBBdd [10, 43].…”

Section: Categorising Update Mechanisms For Graphs Of Subpopulationsmentioning

confidence: 99%

“…For example, MBBdd is adopted in [9, 10, 43]. Not all of the observations made in graphs of individuals with the Bd update rule carry over to a graph of subpopulations when the update rule is MBBdd [10, 43]. In fact, in the graph of subpopulations, the dynamics and, in particular, the fate of advantageous mutants are highly dependent on the pattern of migration, local population size, and the graph structure itself.…”

Section: Categorising Update Mechanisms For Graphs Of Subpopulationsmentioning

confidence: 99%

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Categorising update mechanisms for graph-structured metapopulations

Yagoobi

Sharma

Traulsen

2022

Preprint

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The structure of a population strongly influences its evolutionary dynamics. In various settings ranging from biology to social systems, individuals tend to interact more often with those present in their proximity and rarely with those far away. A common approach to model the structure of a population is Evolutionary Graph Theory. In this framework, each graph node is occupied by a reproducing individual. The links connect these individuals to their neighbours. The offspring can be placed on neighbouring nodes, replacing the neighbours – or the progeny of its neighbours can replace a node during the course of ongoing evolutionary dynamics. Extending this theory by replacing single individuals with subpopulations at nodes yields a graph-structured metapopulation. The dynamics between the different local subpopulations is set by an update mechanism. There are many such update mechanisms. Here, we classify update mechanisms for structured metapopulations, which allows to find commonalities between past work and illustrate directions for further research and current gaps of investigation.

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Mutant fixation in the presence of a natural enemy

Wodarz

Komarova

2023

Preprint

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In the extensive literature about mutant invasion and fixation, populations are typically assumed to exist in isolation from their ecosystem. Yet, populations are part of ecological communities, and enemy-victim (e.g. predator-prey or pathogen-host) dynamics are particularly common. We use computational models to re-visit the established theory about mutant fixation in the presence of a natural enemy, which equally attacks both wild-type and mutant populations. We consider advantageous and disadvantageous mutants, whose fitness is unrelated to the infection. Using spatially structured agent-based as well as patch models of a population that is subject to infection, we investigate the fixation probability of a mutant that is introduced into the population at quasi-equilibrium. We find that infection significantly weakens selection. Thus, the presence of infection increases the fixation probability of disadvantageous mutants and decreases the fixation probability of advantageous mutants, with the magnitude of the effect rising with the infection rate. We show that this occurs because infection induces spatial structures, in which mutant and wild-type individuals are mostly spatially separated. Thus, instead of mutant and wild-type individuals competing with each other, it is mutant and wild-type 'patches' that compete, resulting in smaller fitness differences and hence weakened selection. Because natural enemies such as infections are ubiquitous, this has broad applicability to natural systems. Our results imply that the burden of deleterious mutants in natural populations might be significantly higher than expected from mutant invasion theory developed in the absence of natural enemies.

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Fixation probabilities in network structured meta-populations

Cited by 3 publications

References 50 publications

Impact of population size on early adaptation in rugged fitness landscapes

Impact of population size on early adaptation in rugged fitness landscapes

Categorising update mechanisms for graph-structured metapopulations

Mutant fixation in the presence of a natural enemy

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