Fixation and Fluctuations in Two-Species Cooperation

Fuente: arXiv
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Autori principali: Piñero, Jordi, Redner, S., Solé, Ricard
Natura: Preprint
Pubblicazione: 2021
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author Piñero, Jordi
Redner, S.
Solé, Ricard
author_facet Piñero, Jordi
Redner, S.
Solé, Ricard
contents Cooperative interactions pervade in a broad range of many-body populations, such as ecological communities, social organizations, and economic webs. We investigate the dynamics of a population of two equivalent species A and B that are driven by cooperative and symmetric interactions between these species. For an isolated population, we determine the probability to reach fixation, where only one species remains, as a function of the initial concentrations of the two species, as well as the time to reach fixation. The latter scales exponentially with the population size. When members of each species migrate into the population at rate $λ$ and replace a randomly selected individual, surprisingly rich dynamics ensues. Ostensibly, the population reaches a steady state, but the steady-state population distribution undergoes a unimodal to trimodal transition as the migration rate decreases below a critical value $λ_c$. In the low-migration regime, $λ<λ_c$, the steady state is not truly steady, but instead strongly fluctuates between near-fixation states, where the population consists of mostly A's or of mostly B's. The characteristic time scale of these fluctuations diverges as $λ^{-1}$. Thus in spite of the cooperative interaction, a typical snapshot of the population will contain almost all A's or almost all B's.
format Preprint
id arxiv_https___arxiv_org_abs_2103_10976
institution arXiv
publishDate 2021
record_format arxiv
spellingShingle Fixation and Fluctuations in Two-Species Cooperation
Piñero, Jordi
Redner, S.
Solé, Ricard
Populations and Evolution
Statistical Mechanics
Biological Physics
Cooperative interactions pervade in a broad range of many-body populations, such as ecological communities, social organizations, and economic webs. We investigate the dynamics of a population of two equivalent species A and B that are driven by cooperative and symmetric interactions between these species. For an isolated population, we determine the probability to reach fixation, where only one species remains, as a function of the initial concentrations of the two species, as well as the time to reach fixation. The latter scales exponentially with the population size. When members of each species migrate into the population at rate $λ$ and replace a randomly selected individual, surprisingly rich dynamics ensues. Ostensibly, the population reaches a steady state, but the steady-state population distribution undergoes a unimodal to trimodal transition as the migration rate decreases below a critical value $λ_c$. In the low-migration regime, $λ<λ_c$, the steady state is not truly steady, but instead strongly fluctuates between near-fixation states, where the population consists of mostly A's or of mostly B's. The characteristic time scale of these fluctuations diverges as $λ^{-1}$. Thus in spite of the cooperative interaction, a typical snapshot of the population will contain almost all A's or almost all B's.
title Fixation and Fluctuations in Two-Species Cooperation
topic Populations and Evolution
Statistical Mechanics
Biological Physics
url https://arxiv.org/abs/2103.10976