Fig. 1.

Outbreak dynamics in oak–hickory forests, in data (12), and in a spatial version of an outbreak model that includes induced defenses. A and C are defoliation time series in the data and in the model, respectively, and B and D are the corresponding power spectra. For the model we show a time series based on a single realization, but to ensure that the pattern holds up over multiple realizations, the spectrum for the model is an average over 100 realizations (SI Appendix, Figs. S6–S10 shows more realizations). Because the gypsy moth is an invader and because invasion dynamics could lead to confounding effects, the data are based only on areas that were completely infested by 1975, which in practice meant mostly the New England and Mid-Atlantic sections of the United States (12).