Direct and Indirect Competition in a Two-Prey-One-Predator System : Global Dynamics, Chaos, and the Paine Conjecture
This paper studies the global dynamics of a three-dimensional Lotka-Volterra system of two prey, with direct competition between them, and one predator. Under a symmetry assumption, the rescaled parameter space is sorted into four generic categories, which yield a complete classification of the global dynamics into 56 meaningful subcases. We determine the existence and stability of the boundary and positive equilibria, including global asymptotic stability and bistability of boundary equilibria, and necessary and sufficient conditions for local asymptotic stability of the positive equilibrium. We identify regimes of periodic solutions and chaos, including a period-doubling route to chaos. We further show that the parameters of Gilpin's chaotic dynamics fall within some cases. Biologically, we introduce the notion of extensive negative competition, which, together with trade-off competition and apparent competition, interprets the interactions among the three species. Our classification shows that the full system largely tracks the dynamics of the prey-only subsystem, and these competition mechanisms explain the differences between them, clarifying how predator-mediated interactions alter competitive outcomes and facilitate prey persistence, thereby providing mathematical support for Paine conjecture.