Modeling the invasion of recessive Bt-resistant insects: an impact on transgenic plants.

There is a growing public concern on ecological and evolutionary consequence of the use of genetically modified organisms. We study the impact of Bt-resistant pests on genetically modified Bt crops. We develop and analyse a conceptual reaction-diffusion model of the Bt crop-Bt-susceptible insects-Bt-resistant insects to simulate the invasion of Bt-resistant insects. We show by means of computer simulations that there is a key parameter, which we define as the growth number that characterizes the insects' fitness. We also show that the Bt-resistant insect invasion can lead to inhomogeneity in plant and insect spatial distributions. The plant biomass is found to be essentially dependent on the duration of the Bt-resistant insect reproduction period. There are two types of this dependence. One of them exhibits, respectively, higher plant biomass in comparison with another. The ambiguity in the response of the Bt crop-Bt-susceptible insects system to the invasion of Bt-resistant insects can lead to serious complications in attempts to regulate the dynamics of the system.