ABSTRACT
There is a correlation between the number of plants introduced and the probability of invasion, a phenomenon called “propagule pressure.” For instance, an analysis of catalogs from several nurseries in Britain found that the frequency of sale in the nineteenth century predicted naturalization today (Dehnen-Schmutz et al. 2007a). Another study found that the species whose seeds were sold then at lower prices were more likely to be invasive now, suggesting that they may have been purchased more often because they were less
18.1 Introduction ........................................................................................................................ 259 18.2 Theoretical framework for a horticultural industry model with risk of invasion ... 261
18.2.1 Privately optimal conditions ................................................................................ 262 18.2.2 Socially optimal conditions ..................................................................................264
