Thermal tolerance of Aedes aegypti mosquito eggs is associated with urban adaptation and human interactions

Climate change will profoundly affect mosquito distributions and their ability to serve as vectors for disease, specifically with the anticipated increase in heat waves. The rising temperature and frequent heat waves can accelerate mosquito life cycles, facilitating higher disease transmission. Conversely, higher temperatures could increase mosquito mortality as a negative consequence. Warmer temperatures are associated with urbanized areas, suggesting a need for anthropophilic mosquitoes to adapt to be more hardy to heat stress. Mosquito eggs provide an opportunity to study the biological impact of climate warming as this stage is stationary and must tolerate temperatures at the site of female oviposition. As such, egg thermotolerance is critical for survival in a specific habitat. In nature, Aedes mosquitoes exhibit different behavioral phenotypes, where specific populations prefer depositing eggs in tree holes and prefer feeding non-human vertebrates. In contrast, others, particularly human-biting specialists, favor laying eggs in artificial containers near human dwellings. This study examined the thermotolerance of eggs, along with larval and adult stages, for Aedes aegypti lineages associated with known ancestry and shifts in their host preferences. Mosquitoes collected from areas with high human density showed increased egg viability following high-temperature stress, and a similar, yet more muted effect was noted in larvae. Unlike eggs and larvae, thermal tolerance among adults showed no significant correlation based on the area of collection or human-association. This study underscores that urbanization is a major driver of egg thermotolerance, highlighting the egg stage is likely critical to mosquito survival when associated with humans and needs to be accounted for when predicting future mosquito distribution.