The effects of immigration and environmental variability on the persistence of an inferior competitor

Abstract

We tested the hypothesis that temporally autocorrelated variation should increase the abundance of an inferior competitor sustained by immigration. Temporally autocorrelated variability can increase abundance of the inferior species through effects on demography, the strength of competition, and the mean and variance in the abundance of competing species. We allowed the competitive inferior to immigrate into habitats with constant, variable, or temporally autocorrelated temperature regimes. In the absence of immigration, competitive exclusion occurred, in both constant and variable environments. Immigration permitted persistence of the inferior species, and increased immigration rates led to increased abundance. Temporally autocorrelated variability enhanced this effect of immigration. This 'inflationary' effect suggests that the interplay of immigration and environmental variability can jointly influence the outcome of competitive interactions. Our results suggest that an increase in temporal autocorrelation of environmental variability will cause regional processes to increasingly influence local interactions.