  We investigate the competing effects and relative importance of intrinsic
demographic and environmental variability on the evolutionary dynamics of a
stochastic two-species Lotka-Volterra model by means of Monte Carlo simulations
on a two-dimensional lattice. Individuals are assigned inheritable predation
efficiencies; quenched randomness in the spatially varying reaction rates
serves as environmental noise. We find that environmental variability enhances
the population densities of both predators and prey while demographic
variability leads to essentially neutral optimization.
