Geographic origin and Wolbachia infection influence Aedes aegypti stress tolerance

Aedes aegypti mosquitoes carrying self-spreading, virus-blocking Wolbachia bacteria are being deployed to suppress dengue transmission. Aedes aegypti are widespread across tropical and subtropical regions but their adaptation to local climate conditions is poorly understood. Wolbachia-infected Ae. aegypti are sensitive to environmental conditions, likely contributing to the variable Wolbachia establishment success across release zones in different climates. With releases of Wolbachia-infected Ae. aegypti taking place in the hot and arid city of Jeddah, Saudi Arabia, it is important to understand the interaction between Wolbachia infections and genetic background within this local context. We introduced two Wolbachia transinfections (wAlbB and wMelM) into Ae. aegypti laboratory populations originating from Cairns, Australia and Jeddah, Saudi Arabia. Both wAlbB and wMelM showed complete maternal transmission and reduced infection and dissemination of dengue virus (DENV2) in Saudi Arabian Ae. aegypti, demonstrating their suitability for field release. We then assessed the contributions of genetic background and Wolbachia infection to desiccation, storage and heat stress tolerance. Saudi Arabian Ae. aegypti had lower egg viability but higher adult desiccation tolerance than Australian mosquitoes, with a slower rate of water loss in males, likely reflecting adaptation to local conditions. Wolbachia infection reduced adult heat tolerance in one background and egg viability in both backgrounds, particularly when eggs were exposed to high temperatures or stored before hatching. We also observed differential thermal stability between Wolbachia strains and severe fitness costs of wAlbB infection in females hatching from stored eggs. Wolbachia effects were similar across mosquito backgrounds, but the background effects themselves are expected to influence Wolbachia invasion dynamics, reinforcing the need to use local genotypes for mosquito release programs.