Abstract.  In populations subject to positive density dependence, individuals can increase their fitness by synchronizing the timing of key life history events. However, synchrony represents a perturbation from a population’s stable stage structure, and the accompanying transient dynamics can create troughs of low abundance and promote extinction. Using an ecophysiological model of a mass-attacking pest insect, we show that the effect of synchrony on local population persistence depends on population size and adult lifespan. Results are consistent with a strong empirical pattern of increased extinction risk with decreasing initial population size. Mortality factors such as predation on adults can also affect transient dynamics. Throughout the species range, the seasonal niche for persistence increases with asynchrony. The potential effect of synchrony on persistence may be strongest at the northern range limit, where cold winters tend to synchronize spring colonization, suggesting a role for transient dynamics in the determination of species distributions.

Keywords: ecophysiological model, species range, insect pest, Dendroctonus frontalis, seasonality, positive density dependence, persistence, conspecific attraction