Allee effect increases the dynamical stability of populations

The discrepancy between the frequent complex behaviour of simple population dynamical models and the relative dynamical simplicity of most experimental data encourages theoretical ecologists to revise the basic assumptions of the models. Among many other results, it has been shown recently that sexual reproduction increases dynamical stability, merely because population genetical process;is introduced in the models. Here, we investigate another general consequence of sexual reproduction, the cost of rarity or the Allee effect, from a dynamical point of view. We show that the cost of rarity increases the stability of (the stable) fixed point in a broad class of one-dimensional difference equation systems. The strong stabilization due to the Allee effect is demonstrated by the numerical simulation of a host-microparasite model as well. (C) 1999 Academic Press.