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A bifurcation result for an ecological model via a quadrature method

Nalin Fonseka and Blake Ricketson

Vol. 19 (2026), No. 2, 347–359
Abstract

We study positive solutions to the ecological model of the form

{ u = λf(u), (0,1), u(0) = u(1) = 0,

where λ is a positive parameter proportional to the square of the habitat size, and f(u) = au3 + bu2 + u, where a and b are positive parameters. This type of reaction-diffusion equation specifically models the population density of a species living in a habitat surrounded by a hostile exterior region. In it, our reaction term, f(u) = au3 + bu2 + u, represents a weak Allee growth of the population. This means the per-capita growth rate, f(u)u, is increasing at smaller population densities and decreasing at larger ones. The variable u represents the population density that is a function of the spatial variable x. In our model, the exterior region is extremely hostile, to the point that the population on the boundary has a density of zero. In this study, we discuss the existence of a weak Allee effect for any choices of a and b as well as the structure of positive steady states using a quadrature method. Specifically, we discuss a bifurcation curve modeling this scenario. Further, we present certain numerical results that we obtain using a quadrature method and Mathematica computations.

Keywords
boundary-value problems, ODE, population dynamics, weak Allee growth models
Mathematical Subject Classification
Primary: 34A34, 34B08, 34B15, 34B18, 34C99
Milestones
Received: 5 June 2024
Revised: 22 September 2024
Accepted: 27 September 2024
Published: 8 March 2026

Communicated by Martin Bohner
Authors
Nalin Fonseka
Department of Mathematics, Actuarial Science, & Statistics
University of Central Missouri
Warrensburg, MO
United States
Blake Ricketson
Department of Mathematics, Actuarial Science, & Statistics
University of Central Missouri
Warrensburg, MO
United States