Adaptation and trade-offs with insecticide resistance in overwintering Drosophila

Winter is a formidable challenge for ectotherms that inhabit temperate climates. Prior work has demonstrated that multivoltine organisms can evolve rapidly in response to temporal changes within a growing season, a process termed adaptive tracking. However, the mechanisms by which winter conditions drive rapid adaptation, particularly when combined with strong anthropogenic stressors, remain poorly understood. Here we use replicate populations of Drosophila melanogaster in a field experiment to test i) whether winter conditions drive rapid adaptation and ii) for trade-offs between insecticide resistance and overwintering survival. Following a longitudinal field experiment spanning summer and fall investigating the evolution of insecticide resistance, we tracked subsequent evolution during an overwintering period. We detected repeated evolutionary shifts indicative of adaptation to winter conditions in multiple traits, including body size and fecundity. Additionally, populations that had evolved insecticide resistance during the growing season had reduced survival and showed patterns of lower resistance following the winter period, suggestive of a trade-off between overwintering success and insecticide resistance. These rapid evolutionary responses and potential trade-offs provide important context for understanding overwintering performance in temperate insects, with implications for pest management and ecosystem services.