Abai, MR

6th International Congress of DipterologyAmplification of DNA from preserved specimens showsblowflies were preadapted for the rapid evolution ofinsecticide resistanceHartley, CJ. (1), RD. Newcomb (2), RJ. Russell (1), CG. Yong (2), JR. Stevens (3), DK.Yeates (1), J. La Salle (1) & JG. Oakeshott (1)(1) CSIRO Entomology, PO Box 1700 Canberra ACT 2601 Australia.(2) The Horticulture and Food Research Institute of New Zealand, Private Bag 92169Auckland, New Zealand.(3) Dept of Biological Sciences, University of Exeter, Hatherly Laboratories Prince ofWales Road Exeter EX4 4PS UKMutations of esterase E3 confer two forms of organophosphate resistanceon contemporaryAustralasian Lucilia cuprina. One form, called diazinon resistance, isslightly more effective against commonly used insecticides and is nowmore prevalent than the other form, called malathion resistance. We reporthere that the single amino acid replacement associated with diazinonresistance and two replacements associated with malathion resistance alsooccur in E3 in the sibling species Lucilia sericata, suggesting convergentevolution around a finite set of resistance options. We also find parallelsbetween the species in the geographic distributions of the polymorphisms:in both cases the diazinon resistance change is absent or rare outsideAustralasia where insecticide pressure is lower, whereas the changesassociated with malathion resistance are widespread. Furthermore PCRanalysis of pinned specimens of Australasian L. cuprina collected beforethe release of organophosphate insecticides reveals no cases of thediazinon resistance change but several cases of those associated withmalathion resistance. Thus the early outbreak of resistance in this speciescan be explained by the pre-existence of mutant alleles encoding malathionresistance. The pinned specimen analysis also shows much higher geneticdiversity at the locus prior to organophosphate use, suggesting that thesubsequent sweep of diazinon resistance in Australasia has compromisedthe scope for the locus to respond further to the ongoing challenge of theinsecticides.98