Time scales and species coexistence in chaotic flows

TL;DR

This paper investigates how chaotic flows influence species coexistence by analyzing fixation times in marine ecosystems, revealing that intermediate flow conditions promote long-lasting coexistence due to spatial organization.

Contribution

It introduces a novel analysis of fixation times in chaotic flows, demonstrating the non-linear relationship between flow strength and species coexistence.

Findings

Fixation time is longest at intermediate Damköhler numbers.

Spatial organization on modular networks slows down fixation.

Diffusion can either accelerate or decelerate fixation depending on flow and evolution time scales.

Abstract

Empirical observations in marine ecosystems have suggested a balance of biological and advection time scales as a possible explanation of species coexistence. To characterise this scenario, we measure the time to fixation in neutrally evolving populations in chaotic flows. Contrary to intuition the variation of time scales does not interpolate straightforwardly between the no-flow and well-mixed limits; instead we find that fixation is the slowest at intermediate Damk\"ohler numbers, indicating long-lasting coexistence of species. Our analysis shows that this slowdown is due to spatial organisation on an increasingly modularised network. We also find that diffusion can either slow down or speed up fixation, depending on the relative time scales of flow and evolution.