Short Time Delays in Population Models: A Role in Enhancing Stability

摘要: Analyses of time lags in population models usually concentrate upon delays longer than the dominant scale, a scale defined by shorter return (Tr, which measures tendency perturbed system to its equilibrium) and period oscillation (Tp, cycle.) Many natural can be expected short; here effects such short have been examined both single—level model two—level predator—prey model. I show that due maturation produce variety stability changes, including dramatic decreases increases stability. In model, two important examples are: (1) If recruitment acts regulate around equilibrium, then very delay this term markedly reduce This cautions against routine use self—regulation terms stabilize systems. (2) prey is nonregulatory an otherwise unstable (such as one destabilized type 2 functional response). result generalizes observation made Hastings (1983), found resilient under range conditions, presence distributed delay. suggest there general rule underlying these examples. When isolated from other trophic levels (a rather stringent requirement), enhanced acting through regulatory recruitment. either or itself significantly affected levels, diminished Therefore it processes generally classified destabilizing, lag recruitment, interact increase models.