Mosquito infection-mediated trait variation alters temperature-dependent transmission of West Nile virus

Rising global temperatures are reshaping species interactions and the ecological conditions governing vector-borne disease transmission. Although previous studies show that West Nile virus (WNV) infection alters mosquito longevity, fecundity, blood-feeding behavior, and the thermal performance of these traits, trait-based R₀ models largely rely on data from uninfected mosquitoes, implicitly assuming homogeneous vector populations. This overlooks infection-induced trait variation that may influence transmission dynamics. Here, we examined how temperature, infection status, and viral strain interact to shape transmission potential for WNV in Culex pipiens . Life-history traits of WNV-exposed and unexposed mosquitoes were measured across constant temperatures ranging from 10°C to 33°C, as well as under a fluctuating temperature regime of 25°C ± 5°C. These data were used to generate thermal performance curves and estimate temperature-dependent relative R₀ across treatments. Infection altered the thermal performance of mosquito life-history traits, vector competence, and overall transmission potential. We also found evidence for a bimodal effect of temperature on vector competence, potentially driven by tradeoffs between viral replication and mosquito immune responses. Incorporating infection-sensitive traits into relative R₀ calculations reduced estimated transmission intensity across much of the thermal range without shifting thermal optima or limits, suggesting that current models may overestimate transmission.