Permanence of a Nonlinear Predator-prey-mutualist System

Previous literature has assumed that the infimum of the coefficients of the internal density constraints of all populations in the system is positive when discussing ecosystem permanence. However, this assumption may not hold in a more favorable ecological environment. This paper establishes sufficient conditions to ensure system permanence under the condition that the intraspecies density-dependent coefficient of predators is nonnegative, using comparative theorem combined with subtle analysis skills.