Non-parametric modelling of non-linear density dependence: a three-specieshost-parasitoid system

1. Time-series data from a twice-replicated population experiment (consisti ng of a seed beetle (host), Callosobruchus chinensis, and two parasitoids, Anisopteromalus calandrae and Heterospilus prosopidis) were studied in orde r to identify and to estimate the density-dependent structure. 2. A non-parametric host-parasitoid model based on the Nicholson-Bailey mod el, was studied through non-parametric autoregressive modelling. An additiv e non-linear structure was found in the population growth/parasitism rates for all three species. 3. The analysis suggests that the abundance of A. calandrae only weakly aff ects its own parasitism rate as well as H. prosopidis parasitism rate. 4. The analysis also suggests that the net population growth rate of C chin ensis is highly non-linear, which may be due to disproportionately higher e gg mortality at high adult densities. 5. Non-linearity was also demonstrated in the parasitism rate of H. prosopi dis, which is consistent with assuming that the density-dependent mutual in terference becomes disproportionately higher at high H. prosopidis adult de nsities.