Thermal adaptation in Aedes aegypti does not constrain temperature-sensitive growth of bacteria or dengue virus

Because temperature affects many aspects of the physiology of mosquitoes, including their immune response, anthropogenic climate warming is expected to change the epidemiology and thus the burden of mosquito-borne diseases. However, the impact of temperature on epidemiology may differ from current predictions, if the mosquitoes can adapt evolutionarily to their changing environment. Here, we investigated how thermal adaptation affects the growth of two infectious agents-the bacterium Escherichia coli and dengue virus-in the mosquito Aedes aegypti. We used a panel of mosquito lines that had undergone 19-20 generations of experimental evolution at temperatures from 24°C to 30°C. We assessed the infection of E. coli and dengue virus in each line as a function of adaptation temperature (during experimental evolution) and rearing temperature (during the infection experiment). While increasing rearing temperature enhanced both bacterial and viral growth, adaptation temperature had no detectable main effect on either. The effect of rearing temperature on bacterial growth was only slightly influenced by adaptation temperature. Our findings suggest that thermal adaptation is unlikely to directly affect mosquito immune competence, making one-generation experiments with different rearing generations reliable. We caution that thermal adaptation of mosquitoes may influence other traits underlying pathogen transmission, such as longevity and biting rate. Accounting for the potential for adaptation to modify mosquito thermal responses will improve the predictions of changes in transmission risk due to climate warming.