Impact of niche shift on the spread of Aedes aegypti (Diptera: Culicidae) to and within Japan

Abstract Arbovirus transmission is a global public health concern. The mosquito Aedes aegypti L. (Diptera: Culicidae) is a primary vector of some of these viruses, and its distribution has been a long-term concern because of its vector competence and invasiveness. The invasion and establishment of Ae. aegypti in temperate regions has been extensively discussed, with recent studies reporting phenotypic and evolutionary changes in populations attempting to breed in temperate regions. We used occurrence data from regions with environmental conditions similar to those in Japan to model the potential distribution of Ae. aegypti in Japan, as site-related environmental conditions represent selection pressure for phenotypic and/or evolutionary changes. A random forest model was used for prediction utilizing 3,062 selected occurrence data with a similarity mask. To screen out the drivers affecting adaptability and niche shifts in temperate regions, the above model and a global model using both native and invasive occurrence data were compared. The model predicts that urban areas are the main breeding sites for Ae. aegypti in Japan. Due to competition with the dominant local species, Aedes albopictus Skuse, Ae. aegypti cannot occupy the entire range of urban settings. A niche shift was observed compared to the global model. Niche-shifted populations underwent more rigorous selection for temperature and precipitation, shifting toward human-dwelling environments. These divergences, which warrant further exploration, may be attributed to phenotypic changes or adaptive evolution as mosquito populations persist in temperate regions. The generated prediction maps provide useful insights to understand the expansion of this species.