Habitat Selection under Temporal Heterogeneity: Exorcizing the Ghost of Competition Past

Abstract

We investigate how coexistence between competitors may be influenced by habitat selection when habitats represent either sources or sinks, and given that dispersal is free to evolve. Evolutionary stable dispersal between source and sink habitats can occur if local fitnesses vary temporally, either due to intrinsic factors (e.g., chaotic dynamics) or extrinsic factors (e.g., environmental stochasticity). The model assumes locally linear Lotka- Volterra competition between two species. Given sufficiently low density-independent mortality in the sink, dispersal between habitats is an evolutionary stable strategy (ESS). Given a trade-off between competitive ability in the source and mortality in the sink, a sink habitat can promote species coexistence in the source habitat if the inferior competitor species experiences lower mortality in the sink. This highlights how sink habitats may provide mechanisms of coexistence in heterogeneous landscapes. In a second scenario, the competitors have distinct habitat preferences, resulting in the ‘‘Ghost of Competition Past’’ (i.e., complete habitat partitioning) with stable population dynamics. With unstable population dynamics, dispersal between habitats becomes the ESS, and the Ghost vanishes leading either to coexistence of the competitors in both habitats or global exclusion of one species. Our results highlight the importance of jointly considering the effects of spatial heterogeneity and temporal variability when analyzing the coexistence of competing, mobile organisms.