Population synchrony and environmental variation: an experimental demonstration

Understanding the causes of population synchrony is an important issue for population management. Its study in field populations involves disentanglin g the effects of dispersal and correlated environmental noise. Here we repo rt on an experimental investigation of the synchronizing effects of noise i n closed laboratory populations of a soil mite, Sancassania berlesei. Mite life-histories are highly plastic with respect to resource availability (wh ich is a function of food supply and population density). By varying the fo od supply we imposed environmental variation. We show that (a) population s ynchrony is a function of environmental synchrony, (b) perceived population synchrony depends on the life-history stage counted, and (c) average popul ation synchrony tends to be lower than environmental synchrony: even when p opulations were supplied with food with a correlation of 1.0, the correlati on between populations was 0.63 (bootstrapped 95%CI 0.54-0.71). This suppor ts recent theoretical work suggesting that the Moran theorem (indicating th at population synchrony equals environmental synchrony) generally overestim ates the population synchrony of nonlinear systems.