Modelling to Predict the Fate of Invading Plants

Despite the enormous worldwide effort expended in contending with plant invasions, control -much less eradication -is infrequent. We hypothesized that more effective control (and even eradication) of alien plants would be achieved by recognizing the importance of new foci in an invasion. We based our hypothesis on two observations: 1) The time course for invasions by terrestrial plants follows a logistic curve: a phase in which the new range is invaded slowly is followed by a phase of rapid range expansion. 2) Length of the initial phase of slow spread may be inversely dependent on the number of initial foci. Dividing a focus into many isolated foci will enormously increase the rate of new range occupation, assuming the same expansion rate for all foci (Mack 1985).