A lattice gas model is applied to a mating system composed of one female and two males. Both males have different fertilities. Basic differential equations exhibit a bifurcation between extinction and Allee-effect phase. From biological meanings, we conjecture not only a Lyapunov function but also the densities at equilibrium. We discuss the different roles between high- and low-reproductive males for species conservation.

lattice gas model, male-female system, population dynamics, Allee effect, Lyapunov function, two-male species, bifurcation, phase transition.