Figure 1: Compare the parameter regions of coexistence when the predator and prey are with Allee effect (shaded area) with those when they are without Allee effect, respectively. The area between lines a and b is the regions of coexistence when the predator-prey system is without Allee effect. (a) The situation of the predator with Allee effect. Parameter values are , , and ; (b) the situation of the prey with Allee effect. Parameter values are , , and .