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

Abstract

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 LotkaVolterra 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.

Habitat Selection and Population Regulation in Temporally Fluctuating Environments

“…However, a full-blown ESS analysis is out of scope here; such an analysis may be the next step to study habitat selection in a stochastic environment in the face of uncertainty. Schmidt et al (2000) suggest ways for finding ESS behaviors for similar sorts of dilemmas, and their article provides a starting point.…”

“…That variation can be a property of the habitat itself or a consequence of the number of individuals using the habitat in concert with the consequences of density dependence. Attempts to include temporal variation in habitat quality assume either a constant rate of movement between habitats, which means that individuals cannot assess or respond to changes in habitat quality from year to year (e.g., Schmidt et al 2000;Holt and Barfield 2001), or only one of two habitats has fluctuating resources (Recer et al 1987). In natural systems, resources fluctuate in both time and space, and such environmental stochasticity generates spatiotemporal variation in population density.…”

Ecosystem-phase interactions: aquatic eutrophication decreases terrestrial plant diversity in California vernal pools

“…Seasonal Xuctuations, whether regular or irregular, are a ubiquitous occurrence that can greatly alter ecosystem characteristics and functioning (e.g., Sanders et al 1989;Fahrig 1992;Oksanen 1990;Schmidt et al 2000;Mehner et al 2005). While most studies focus on a single community (i.e.…”

Competition and habitat use in native Australian Rattus: is competition intense, or important?

“…The concept of intensity versus importance of competition is similar to the "ghost of competition past" (Rosenzweig 1981), which accounts for the co-existence of habitat-selecting competitors in separate habitats under the continuing threat of competition. The ghost is difficult to see in contemporary situations, but can be identified from patterns of habitat use that emerge among competitor species during fluctuations in their population densities (Morris et al 2000; see also Schmidt et al 2000).…”