Increases and decreases in network synchrony associated with local population extinction and recolonization

Abstract

Synchronous population dynamics, a positive correlation in growth rates among populations, is of interest from basic and applied perspectives. Synchronous dynamics are ubiquitous in nature thus understanding the mechanisms producing synchrony is fundamental. Population networks with synchronous dynamics have shorter persistence times than asynchronous networks, thus understanding its sources may aid conservation. Previous research has shown that the extinction and recolonization of local populations within a spatial population network produces a decrease in synchrony; however, models investigating extinction alone have shown increases in synchrony and the potential for increased network wide extinction risk. Here, I investigated these contrasting results. At low population growth rates, r=1.1, the extinction and recolonization of a local population increased the synchrony of surrounding populations. Also in contrast to previous results, at higher growth rates, r>2.1, extinction–recolonization dynamics resulted in a range of results – increasing, decreasing, and no change in synchrony. In all cases, the impact of extinction and recolonization dynamics on synchrony depended on whether dispersal was local or global, the population growth rate, the emigration rate, and the amount of local stochasticity. Results indicate that there is a high potential for positive feedback of local extinction and recolonization on network-wide extinction risk for patchy populations of species with low intrinsic growth rates.