  We prove the existence of traveling fronts in diffusive Rosenzweig-MacArthur
and Holling-Tanner population models and investigate their relation with fronts
in a scalar Fisher-KPP equation. More precisely, we prove the existence of
fronts in a Rosenzweig-MacArthur predator-prey model in two situations: when
the prey diffuses at the rate much smaller than that of the predator and when
both the predator and the prey diffuse very slowly. Both situations are
captured as singular perturbations of the associated limiting systems. In the
first situation we demonstrate clear relations of the fronts with the fronts in
a scalar Fisher-KPP equation. Indeed, we show that the underlying dynamical
system in a singular limit is reduced to a scalar Fisher-KPP equation and the
fronts supported by the full system are small perturbations of the Fisher-KPP
fronts. We obtain a similar result for a diffusive Holling-Tanner population
model. In the second situation for the Rosenzweig-MacArthur model we prove the
existence of the fronts but without observing a direct relation with Fisher-KPP
equation. The analysis suggests that, in a variety of reaction-diffusion
systems that rise in population modeling, parameter regimes may be found when
the dynamics of the system is inherited from the scalar Fisher-KPP equation.
