Double Allee effects in a simple tri-trophic system exhibit positive correlation with coexistence and species biodiversity

The Allee effect is a well-known phenomenon that occurs in numerous populations when species densities are low. Many studies have focused on the Allee effect in prey populations, but there is limited research on the mechanism of Allee effects in predators. In multi-trophic systems, predators often experience low population densities due to insufficient food availability, which may lead to Allee effects more frequently in predators than in prey. In this study, a simple tri-trophic model consisting of bottom prey, middle predator and top predator is developed under three different scenarios: when the Allee effect is imposed only on the bottom prey, only on the top predator and simultaneously on both the bottom prey and top predator. The comparative studies are carried out for all the developed models, from which it is observed that the presence of a double Allee effect results in a larger stability domain within the three-species food chain model. This suggests that the double Allee effect has significant control over the coexistence and persistence of the tri-trophic model.