Population model of fluctuations in organophosphate resistance of <Emphasis Type="Italic">Drosophila melanogaster</Emphasis>: Roles of a mutated acetylcholinesterase and a cytochrome P450

The dynamics of genetic variation in susceptibility to insecticides within a natural population of Drosophila melanogaster (Meigen) was examined using model systems and experimental data published previously. In a recent study, two resistance factors for three organophosphate insecticides (OPs) were suggested to be involved within the Katsunuma population (Yamanashi Prefecture, Japan): a resistant-type acetylcholinesterase (AChE) and a cytochrome P450 monooxygenase (cytochrome P450). Within this natural population, the relative contributions of the resistanttype AChE to genetic variation in resistance to the three OPs were larger than those of the cytochrome P450. The simulation analysis by means of the model, based on genotypic density-independent population projection trajectories, suggested that seasonal fluctuations of genetic variation in resistance to the three OPs were mainly caused by the change in the frequency of the resistant-type acetylcholinesterase (Ace) gene within the population.