The biology of Aedes albopictus invasion capacity

Aedes albopictus is one of the most invasive mosquito species globally and it is responsible for the re-emergence of several arboviral diseases in both tropical and temperate regions of the world. Its rapid expansion has been linked to traits such as diapause, desiccation-resistant eggs and adaptability to urban environments. However, Ae. albopictus populations show variation in other phenotypic traits, including reproductive capacity and thermal tolerance, which could impact Ae. albopictus invasion success especially as the climate crises progress. On this basis, my PhD thesis aimed at studying Ae. albopictus thermal resilience to heatwaves (HWs) and its reproductive capacity, to unravel the impact of these traits on the invasion capacity of Ae. albopictus. I designed two separate projects to study each trait. Because the increase in the frequency and intensity of HWs under global warming is expected to have more dramatic biological impacts on insects than mean temperature increases, in the first project I examined the biological consequences of an ecologically relevant HW on the different life stages of Ae. albopictus. Through fitness assessments, physiological measurements, transcriptomics, and microbiota profiling, I found stage- and sex-specific responses to heat stress. Eggs and males were most vulnerable stages, with high embryo mortality and male mortality following exposure to HW. In contrast, larvae and females exhibited thermal resilience: larvae delayed development and upregulated heat shock proteins, while females showed extensive transcriptional shifts involving oxidative stress pathways and metabolic adjustments. Notably, only blood-fed females exhibited reduced reproductive output post-HW, suggesting that recovery periods within HWs may mitigate some reproductive costs. These findings highlight the multifaceted nature of mosquito thermal tolerance and underscore the ecological importance of studying multiple traits across developmental stages. Together, these results provide valuable data to refine predictive models and design adaptive control strategies under climate change. In the second project, I combined fitness analyses, physiological assays, proteomics, and genomics to compare the reproductive capacity of laboratory populations of Ae. albopictus. I found that mosquitoes from invasive areas optimize nutrient allocation during development and oogenesis, leading to higher fecundity despite delayed egg production. Mosquitoes from invasive populations displayed longer larval development, larger adult size, and more efficient blood digestion. Their fat bodies and ovaries were protein enriched despite reduced blood intake. Additionally, lipid and protein deposition into developing oocytes was more coordinated. Reciprocal crosses between long laboratory adapted and invasive mosquitoes revealed heterosis, with hybrid offspring exhibiting higher fertility than both parents, indicating a genetic component to this increased reproductive capacity. These findings suggest that physiological and genetic adaptations in reproductive investment contribute to the invasion success of Ae. albopictus. Together, these studies offer new insights into the adaptive strategies that support Ae. albopictus’ global expansion. By highlighting the importance of heat resilience and reproductive capacity, this work contributes to a better understanding of the ecological success of this invasive vector and offers valuable perspectives for future control strategies in the face of climate change.