Insecticide Resistance Alters Oviposition Preference in Drosophila melanogaster

Environmental pressures, particularly those driven by anthropogenic activity, can induce rapid behavioural and physiological adaptation. Insects, due to their ecological importance, are especially affected by the widespread use of insecticides. While physiological resistance to insecticides is well documented, less is known about how such resistance influences behaviour, particularly oviposition site choice, a decision with direct consequences for offspring survival. Using Drosophila melanogaster, we investigated whether genetic resistance conferred by the detoxification gene Cyp6g1 affects oviposition preferences and survival across life stages when exposed to insecticides. We presented resistant and susceptible female flies with a choice between food laced with acetone, insecticides to which they are resistant, or insecticides to which Cyp6g1 does not confer resistance, and examined larval and adult survival under matching exposure conditions. We found that resistant females differ from susceptible flies by avoiding laying eggs on food containing DDT, an insecticide they are resistant to, suggesting that resistance is associated with a parallel shift in behaviour. Larval survival was closely tied to maternal oviposition choice, with Cyp6g1-mediated resistance conferring survival benefits only against insecticides it can detoxify. In contrast, adult survival was less affected by genotype, highlighting the importance of oviposition site selection in shaping transgenerational fitness. Our results suggest that resistance alleles can impact not only physiological resistance but also incur behavioural adaptations such as toxin avoidance that act synergistically to mitigate insecticide exposure. Furthermore, our results show that these resistance alleles influence behaviour in ways that affect their frequency in natural populations.