Complex dynamics in plant-pollinator-parasite interactions: facultative versus obligate behaviors and novel...

Understanding the dynamics of plant-pollinator interactions is crucial for maintaining ecosystem stability and biodiversity. In this paper, we formulate a novel tripartite plant-pollinator-parasite model that incorporates the influence of parasites on mutualistic relationships. Our model consists of the plant-pollinator subsystem, which exhibits equilibrium dynamics with up to four bistable states; the pollinator-parasite subsystem, where stability is significantly affected by pollinator density and growth rate; and the complete system combining all three species. We perform comprehensive mathematical and bifurcation analyses on both the subsystems and the full system. We have many interesting findings, including that (1) plant-pollinator-parasite interactions are dependent on the properties of plants and pollinators (i.e., facultative or obligate interactions). For example, systems with facultative pollinators are more likely to exhibit multistability and periodic oscillations, thereby enhancing resilience, whereas scenarios with obligate pollinators are more likely to lead to system collapse. (2) Critical parameters such as parasite mortality and conversion rates can drive complex behaviors, including supercritical and subcritical Hopf bifurcations, saddle-node bifurcations, chaos, and heteroclinic orbits. Notably, we introduce three new concepts-the left bow, right bow, and wave bow phenomena-to characterize variations in oscillation amplitude resulting from parameter bifurcations. These important results provide theoretical guidance for ecological management strategies aimed at enhancing ecosystem resilience and stability by considering the complex interactions among plants, pollinators, and parasites.