Reflections on niches and numbers

Environmental factors control spatial distributions and local abundances in distinct – but overlapping – ways. Osorio-Olivera et al. examine when environments near the geometric center of a species' ecological niche – which they assume to be optimal for growth when rare – also harbor the greatest number of individuals on average at equilibrium, and when not. Transient dynamics, Allee effects and metapopulation dynamics can cloud this relationship. In this brief piece I sketch a number of further ways in which this relationship can break down, including asymmetry in the shape of the niche, spatial variation in density dependence, and nonlinear feedbacks with the environment.