Dietary landscapes shape genotype- and sex-specific responses to insecticides

How resistance alleles interact with nutritional environments to shape fitness remains largely unknown. Here we combine nutritional geometry approaches to test how variation at a major resistance locus, <i>Cyp6g1</i>, modifies sex-specific reproductive performance across dietary landscapes in <i>Drosophila melanogaster</i>.

We show that a resistance allele does more than increase survival: it profoundly reshapes reproductive allocation in both sexes. Resistant females exhibited up to a two-fold increase in ovariole number, with benefits amplified in protein-rich, high-calorie diets. In contrast, resistant males displayed increased testis size but reduced seminal vesicle and accessory gland size, revealing sex-specific trade-offs.