Models for the introgression of a transgene into a wild population within a stochastic environment, with applications to pest control

Several forms of control are currently under consideration for pest species in Australia. Perhaps the most novel makes use of either an inducible fata lity gene (IFG) or an inducible sterility gene (ISG). The transgene is inte grated into the genome of target populations by periodically releasing tran sgenic animals. When high proportions of the population carry the transgene then the gene may be induced to reduce abundance. A fundamental feasibilit y issue is how much time and effort is required before the proportion of th e population carrying the transgene reaches values close to 1. It is shown that the speed of introgression may be underestimated if models do not allo w for year-to-year variability in natural processes, such as the number of young arising from natural breeding or the number of adults surviving to br eed. Furthermore, the improvements in speed of introgression due to variabi lity are magnified for species with lower lifespans. We include, as specifi c examples, application of the model to common carp (Cyprinus carpio) and m osquitofish (Gambusia affinis), which are major freshwater pests in Austral ia. (C) 1999 Elsevier Science B.V. All rights reserved.