Lattice-based stochastic models motivate non-linear diffusion descriptions of memory-based dispersal

TL;DR

This paper introduces a lattice-based stochastic model for animal movement that incorporates memory effects, deriving a novel nonlinear diffusion PDE that accurately reflects individual-based movement mechanisms and their influence on population dispersal.

Contribution

It presents the first derivation of a nonlinear diffusion PDE from a lattice-based stochastic model with memory-dependent movement, linking individual behavior to population-level dispersal.

Findings

The PDE accurately models stochastic simulation outcomes.

Memory effects significantly influence dispersal patterns.

The model provides a biologically intuitive framework for memory-based movement.

Abstract

The role of memory and cognition in the movement of individuals (e.g. animals) within a population, is thought to play an important role in population dispersal. In response, there has been increasing interest in incorporating spatial memory effects into classical partial differential equation (PDE) models of animal dispersal. However, the specific detail of the transport terms, such as diffusion and advection terms, that ought to be incorporated into PDE models to accurately reflect the memory effect remains unclear. To bridge this gap, we propose a straightforward lattice-based model where the movement of individuals depends on both crowding effects and the historic distribution within the simulation. The advantage of working with the individual-based model is that it is straightforward to propose and implement memory effects within the simulation in a way that is more biologically intuitive than simply proposing heuristic extensions of classical PDE models. Through deriving the continuum limit description of our stochastic model, we obtain a novel nonlinear diffusion equation which encompasses memory-based diffusion terms. For the first time we reveal the relationship between memory-based diffusion and the individual-based movement mechanisms that depend upon memory effects. Through repeated stochastic simulation and numerical explorations of the mean-field PDE model, we show that the new PDE model accurately describes the expected behaviour of the stochastic model, and we also explore how memory effects impact population dispersal.