Electron. J. Diff. Equ., Vol. 2015 (2015), No. 02, pp. 1-20.

Stability of mutualisms in a lattice gas system of two species

Yuanshi Wang, Hong Wu

Abstract:
This article considers mutualisms in a lattice gas system of two species. The species are mutualistic since each one can provide resources to the other. They are also competitive since they compete for empty sites on the same lattice. The mutualisms are assumed to have a saturated response, and the intraspecific competition is considered because of self-limitation. The mutualism system is characterized by differential equations, which are derived from reactions on lattice and are extension of a previous model. Global stability analysis demonstrates that (i) When neither species can survive alone, they can coexist if mutualisms between them are strong and population densities are large, which exhibits the Allee effect in obligate mutualism; (ii) When one species can survive alone but the other cannot, the latter one will survive if the mutualistic effect from the former is strong. Even if the effect is intermediate, the latter species can survive by strengthening its mutualistic effect on the former and enhancing its population density; (iii) When either species can survive alone, a weak mutualism will lead to extinction of one species. When in coexistence, intermediate strength of mutualism is shown to be beneficial under certain parameter range, while over- or under- mutualism is not good. Furthermore, extremely strong/weak mutualism is exhibited to result in extinction of one/both species. While seven typical dynamics are displayed by numerical simulation in a previous work, they are proved in this work and the eighth one is exhibited. Numerical simulations validate and extend our conclusions.

Submitted November 19, 2014. Published January 5, 2015.
Math Subject Classifications: 34C37, 92D25, 37N25.
Key Words: Stability; persistence; cooperation; saddle-node bifurcation; Holling Type II functional response.

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Yuanshi Wang
School of Mathematics and Computational Science
Sun Yat-sen University, Guangzhou 510275, China
email: mcswys@mail.sysu.edu.cn
Hong Wu
School of Mathematics and Computational Science
Sun Yat-sen University, Guangzhou 510275, China
email: wuhong@mail.sysu.edu.cn

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