Figure 2.

Temporal spacing of immigration influences establishment in a sink with an Allee effect. Cumulative immigrants per run of 100 generations was 300; initial density was 1. Immigration pulses were larger in runs with fewer pulses. (a) Effect of immigration spacing on mean abundance, averaged over the last immigration cycle. (b) and (c) show typical trajectories. (b) Constant immigration (three per generation)—the population stays trapped at low numbers (were immigration eliminated, extinction ensues). (c) Pulses each 10 generations; the population ratchets towards establishment; i.e., persistence without immigration. Intrinsic growth rate r = 1.1, α (Allee threshold) = 40, carrying capacity K = 100. See the electronic supplementary material for details and explorations of parameter space.