Di Castri, S. | bioRxiv Science

bioRxiv2026

Microbiota-driven, strain-specific Asaia colonisation modulates mosquito vector competence

Microbiota-based mosquito control strategies are founded on the ability of bacterial symbionts to modify host biology and/or pathogen transmission. However, symbionts do not operate in isolation. Their colonisation, persistence and biological effects arise within a complex ecological network comprising the host and its resident microbiota. We hypothesized that colonisation success is not only an intrinsic property of a bacterial symbiont but emerges from interactions between bacterial strain, host background, and the native microbial community. To test this, we compared recolonisation by endogenous and exogenous Asaia strains in the invasive mosquito Aedes koreicus using wild-type and axenic mosquitoes to experimentally manipulate the microbial composition. We found that endogenous and exogenous strains followed distinct colonisation trajectories. Depletion of the resident microbiota selectively rescued colonisation by the endogenous strain, whereas both strains successfully disseminated to transmission-relevant tissues despite contrasting early gut dynamics. Furthermore, these strain-specific colonisation dynamics were associated with increased Semliki Forest virus (SFV) transmission and enhanced adult longevity, particularly following colonisation by the exogenous strain. Our findings indicate that resident microbial communities act as selective ecological filters that shape symbiont colonisation in a strain-dependent manner. More broadly, this study demonstrates that the biological effects of mosquito symbionts emerge from interactions between bacterial strains and the microbial community context, providing an ecological framework for the rational and effective development of microbiota-based vector control strategies.

microbiology↗

bioRxiv2026

Evidence of thermal selection from experimental evolution in the arboviral vector Aedes albopictus

The extent to which phenotypic plasticity and adaptation are coupled during ectotherm thermal evolution is poorly understood. We carried out thermal experimental evolution for 20 generations in the arboviral vector Aedes albopictus, an efficient invasive species that has newly conquered climatically diverse regions in the past few decades. During acclimation (one generation of evolution) we saw accelerated development and increased reproduction that traded off against survival. After only another 10 generations, we saw adaptation in the form of major changes in mosquito fitness, metabolism and gene expression, revealing the consolidation of a temperature-dependent trade-off between reproduction and longevity. These shifts demonstrate that Ae. albopictuscan adapt at the pace of warming. When selection was relaxed, most of the thermally shifted phenotypes reverted to control levels, revealing the importance of plasticity after prolonged evolution. Furthermore, 250 warm evolution-altered genes did not return to control levels. These genes exhibited significant negative correlation between mean and variance in warm-evolved mosquitoes, but a two-fold variance reduction without mean change in relaxed-selection mosquitoes. Both signals are consistent with the action of selection operating on a polygenic trait architecture. Ecological modelling identified egg-to-adult viability as the primary driver of thermal reproductive success, highlighting juvenile stages as a crucial control target under continued warming.

evolutionary biology↗