Evidence of thermal selection from experimental evolution in the arboviral vector Aedes albopictus

Whether global warming drives thermal adaptation in arboviral vectors is an open question with direct consequences for forecasting transmission risk and informing effective vector control strategies. We subjected Aedes albopictus to experimental evolution (EE) under a tropical thermal regime (32{degrees}C/26{degrees}C) for three years and tracked fitness and behavioral traits, energy reserves and the fat body transcriptional profile across replicate lines at defined generational intervals. We show that mosquitoes strongly acclimate, trading longevity for accelerated development and increased reproduction. Over 15-20 generations of EE, mosquitoes gradually adjusted adult longevity to values of controls, reproductive traits reduced while maintaining values higher than those of controls, and the transcriptome converged to a distinct metabolic state. Upon relaxing thermal selection, half of the transcriptional changes of warm-evolved mosquitoes, along with traits of juvenile development and adult lifespan, reversed to values of controls, indicating a plastic basis. In contrast, progeny per female and egg freeing point maintained warm-evolved values upon relaxing thermal selection. Moreover, the mean and variance of 250 differentially expressed genes showed a significant correlation in warm-evolved mosquitoes, with a considerable reduction of expression variance upon relaxing thermal selection, signatures consistent with selection acting on a polygenic trait architecture. Modelling of the net reproductive rate across generations showed that egg-to-adult viability, not fecundity or longevity, is the primary driver of reproductive success under warm evolution. Our findings have immediate methodological and ecological implications: clinal studies or single-generation exposures risk attributing to adaptation changes driven by phenotypic plasticity, acclimation, genetic drift or population structure.