Survey of malathion resistance and avermectin susceptibility in field populations of Drosophila melanogaster (Diptera: Drosophilidae) and D. simulans

Populations of Drosophila melanogaster (Meigen) and Drosophila simulans (Sturtevant) from various geographic locations in North America and elsewhere were sampled to assess the distribution of malathion resistance and avermectin tolerance. Comparisons are made to previous reports of a differential response to malathion selection in these species. Results indicate that for malathion, resistance is widespread in D. simulans but varies considerably in D. melanogaster. For avermectins, although the pattern of tolerance is similar in both species, there exists a significant amount of variation in these levels between geographic regions. We consider how these different geographic patterns of resistance distribution may shed insight on the relative roles of population structure and exposure history in affecting the spread of resistance. In addition, we consider further the use of D. melanogaster and D. simulans as a model for examining the effects of insecticide exposure on sympatric populations.