Population persistence under advection-diffusion in river networks

TL;DR

This paper models population dynamics in river networks using an integro-differential equation with advection-diffusion processes, deriving conditions for population extinction based on eigenvalue bounds.

Contribution

It introduces a novel mathematical framework for population persistence in river networks using integro-differential equations and eigenvalue analysis.

Findings

Derived bounds for eigenvalues of the dispersion operator

Established sufficient conditions for population extinction

Linked physical variables to extinction thresholds

Abstract

An integro-differential equation on a tree graph is used to model the evolution and spatial distribution of a population of organisms in a river network. Individual organisms become mobile at a constant rate, and disperse according to an advection-diffusion process with coefficients that are constant on the edges of the graph. Appropriate boundary conditions are imposed at the outlet and upstream nodes of the river network. The local rates of population growth/decay and that by which the organisms become mobile, are assumed constant in time and space. Imminent extinction of the population is understood as the situation whereby the zero solution to the integro-differential equation is stable. Lower and upper bounds for the eigenvalues of the dispersion operator, and related Sturm-Liouville problems are found, and therefore sufficient conditions for imminent extinction are given in terms of the physical variables of the problem.