Consequences of parameterization and structure of applied demographic models: a comment on Pardini et al. (2009).

Correcting the problems in the model of A. petiolata presented in Pardini et al. (2009) changes its dynamics and thus the management recommendations. As with any model, our revised model's-management predictions are conditional on model parameterization. Thus, managers should carefully consider at what spatial scales it is appropriate to infer management recommendations given the data used to build the model (e.g., is a management plan developed from a population in Missouri equally relevant to populations in Georgia, Maine, and Oregon?). In agreement with PDCK's conclusions, we found their A. petiolata study population to exhibit complex dynamics (two-point cycling) at lower efficacies of either rosette or adult management, and stable equilibria at higher management efficacies. This could have important implications for A. petiolata management techniques such as biological control if the biocontrol agents' population dynamics are dependent on A. petiolata density. While the predictions generated in our reanalysis represent an improvement over the original model, they should be tempered by the limited scope of the data used to parameterize the model. Running the model through previously published parameter ranges results in qualitatively different dynamics than those predicted in PDCK. Because of the tremendous spatiotemporal variability in A. petiolata demographic rates and the species' large geographical range, more general management recommendations will only arise from a larger set of demographic data that has greater coverage in space and time. Our revision of the model of Pardini et al. (2009) should therefore be considered as a subset of many possible models of A. petiolata population dynamics.