  How diffusion impacts on ecological dynamics under the Allee effect and
spatial constraints? That is the question we address. Employing a microscopic
minimal model in a metapopulation (without imposing nonlinear birth and death
rates) we evince --- both numerically and analitically --- the emergence of an
optimal diffusion that maximises the survival probability. Even though, at
first such result seems counter-intuitive, it has empirical support from recent
experiments with engineered bacteria. Moreover, we show that this optimal
diffusion disappears for loose spatial constraints.
