Evolutionary and Population Dynamics: A Coupled Approach

TL;DR

This paper explores how population growth and evolutionary processes interact in microbial populations, revealing that their interplay can lead to different behaviors such as increased cooperation, validated through simulations and analytical models.

Contribution

It introduces a coupled stochastic model for population and evolutionary dynamics, highlighting the impact of population size fluctuations on cooperation evolution.

Findings

Cooperation can increase transiently due to demographic fluctuations.

Different growth scenarios lead to qualitatively different behaviors.

A condition for the increase in cooperation level is derived.

Abstract

We study the interplay of population growth and evolutionary dynamics using a stochastic model based on birth and death events. In contrast to the common assumption of an independent population size, evolution can be strongly affected by population dynamics in general. Especially for fast reproducing microbes which are subject to selection, both types of dynamics are often closely intertwined. We illustrate this by considering different growth scenarios. Depending on whether microbes die or stop to reproduce (dormancy), qualitatively different behaviors emerge. For cooperating bacteria, a permanent increase of costly cooperation can occur. Even if not permanent, cooperation can still increase transiently due to demographic fluctuations. We validate our analysis via stochastic simulations and analytic calculations. In particular, we derive a condition for an increase in the level of cooperation.