Changes in the cyclicity of herbivore populations along latitudinal gradients and the underlying effects of trophic interactions have long been a matter of intense interest. In contrast, elevational gradients in population cyclicity are largely unexplored. We investigate the cyclicity of gypsy moth populations along an elevational gradient by applying wavelet analysis to a 31-yr record (1975-2005) of defoliation maps. In addition, a simulation model of multitrophic interactions between gypsy moths, a major generalist predator of the gypsy moth (the white-footed mouse), the primary winter food source of the mouse (red oak acorns), and a viral pathogen of the gypsy moth was used to explore how gypsy moth population dynamics may be affected by an elevational gradient in generalist-predator density.
Results/Conclusions
Results from the wavelet analysis show that the cyclicity of gypsy moth populations was more pronounced at high elevations. In addition, the length of the dominant period of population fluctuations decreased with increasing elevation. Results from the simulation model suggest that higher predation pressure from the generalist predator at low elevation can explain the relative lack of cyclical behavior and longer period lengths of gypsy moth population fluctuations at low elevation.
