Abstract
Aedes aegypti mosquito eggs can remain quiescent for many months before hatching, allowing populations to persist through unfavourable conditions. A. aegypti infected with the Wolbachia strain w Mel have been released in tropical and subtropical regions for dengue control. w Mel reduces the viability of quiescent eggs, but this physiological cost might be expected to evolve in natural mosquito populations that frequently experience stressful conditions. We found that the cost of w Mel infection differed consistently between mosquitoes collected from different locations and became weaker across laboratory generations, suggesting environment‐specific adaptation of mosquitoes to the w Mel infection. Reciprocal crossing experiments show that differences in the cost of w Mel to quiescent egg viability were mainly due to mosquito genetic background and not Wolbachia origin. w Mel‐infected mosquitoes hatching from long‐term quiescent eggs showed partial loss of cytoplasmic incompatibility and female infertility, highlighting additional costs of long‐term quiescence. Our study provides the first evidence for a shift in Wolbachia phenotypic effects following deliberate field release and establishment and it highlights interactions between Wolbachia infections and mosquito genetic backgrounds. The unexpected changes in fitness costs observed here suggest potential tradeoffs with undescribed fitness benefits of the w Mel infection.