EVIDENCE FOR GENETIC HITCHHIKING EFFECT ASSOCIATED WITH INSECTICIDE RESISTANCE IN AEDES-AEGYPTI

Information on genetic variation within and between populations is cri tical for understanding the evolutionary history of mosquito populatio ns and disease epidemiology. Previous studies with Drosophila suggest that genetic variation of selectively neutral loci in a large fraction of genome may be constrained by fixation of advantageous mutations as sociated with hitchhiking effect. This study examined restriction frag ment length polymorphisms of four natural Aedes aegypti mosquito popul ations from Trinidad and Tobago, at 16 loci. These populations have be en subjected to organophosphate (OP) insecticide treatments for more t han two decades, while dichlor-diphenyltrichlor (DDT) was the insectic ide of choice prior to this period. We predicted that genes closely li nked to the OP target loci would exhibit reduced genetic variation as a result of the hitchhiking effect associated with intensive OP insect icide selection. We also predicted that genetic variability of the gen es conferring resistance to DDT and loci near the target site would be similar to other unlinked loci. As predicted, reduced genetic variati on was found for loci in the general chromosomal region of a putative OP target site, and these loci generally exhibited larger F-ST values than other random loci. In contrast, the gene conferring resistance to DDT and its linked loci show polymorphisms and genetic differentiatio n similar to other random loci. The reduced genetic variability and ap parent gene deletion in some regions of chromosome 1 likely reflect th e hitchhiking effect associated with OP insecticide selection.