Figure 4.

Density dependence in Phytobia populations. Phase plots of per capita rate of increase, r_t = ln (N_t/N_t−1), of Phytobia populations at Peikkola and Valtatie plotted against lagged population densities (N_t−1 and N_t−2) after detrending the time series with the general linear model described in Table 1 and Fig. 2. The best linear response surface models (Table 1) were a second-order time series model (r_t = 1.076–0.198 N_t−1 − 0.086 N_t−2, r² = 0.45) for Peikkola population, and a first-order time series model (r_t = 0.576–0.069 N_t−1, r² = 0.25) for Valtatie population.