AN OVERVIEW OF THE EVOLUTION OF OVERPRODUCED ESTERASES IN THE MOSQUITO CULEX-PIPIENS

Insecticide resistance genes have developed in a wide variety of insec ts in response to heavy chemical application. Few of these examples of adaptation in response to rapid environmental change have been studie d both at the population level and at the gene level. One of these is the evolution of the overproduced esterases that are involved in resis tance to organophosphate insecticides in the mosquito Culex pipiens. A t the gene level, two genetic mechanisms are involved in esterase over production, namely gene amplification and gene regulation. At the popu lation level, the co-occurrence of the same amplified allele in distin ct geographic areas is best explained by the importance of passive tra nsportation at the worldwide scale. The long-term monitoring of a popu lation of mosquitoes in southern France has enabled a detailed study t o be made of the evolution of resistance genes on a local scale, and h as shown that a resistance gene with a lower cost has replaced a forme r resistance allele with a higher cost.