On the risk of extinction of a wild plant species through spillover of a biological control agent: analysis of an ecosystem compartment model

Invasive plant species can be controlled by introducing one or more of their natural enemies (herbivores) from their native range; however such introduction entails the risk that the introduced natural enemy will attack indigenous plant species in the area of introduction. The effect of spillover of a natural enemy from a managed ecosystem compartment (agriculture) in the area of introduction to a natural compartment (non-managed) in which an indigenous plant species is attacked by the introduced natural enemy, whereas another indigenous plant species, which competes with the first, is not attacked, has been studied. The combination of competition and herbivory may result in extinction of the attacked wild plant species. Using a modelling approach, the authors have determined model parameters that characterize the risk of extinction. The findings point to the importance of spillover and the relative attack rates (specificity) of introduced natural enemies with respect to target and non-target plant specie