Genetics of range expansion and admixture of Aedes aegypti populations in California.

BACKGROUND: The mosquito Aedes aegypti, a key vector for arboviruses including dengue, Zika, and chikungunya, was first detected in California in 2013 and has since expanded northward. This study examines the genetic structure of California populations and, based on that structure, proposes potential mechanisms driving their invasion across the state. RESULTS: A whole-genome analysis of 181 individuals, including 49 newly sequenced from recently established populations in Northern California, corroborates previously described genetic structure and reveals the origins of these populations. Many northern populations shared ancestry with Southern California populations, suggesting passive dispersal. Additionally, we observed significant genetic admixture between divergent clusters in the Central Valley, associated with increased nucleotide diversity, which may enhance adaptive potential. We describe the effects of range expansion and genetic admixture on divergent ancestral lineages and discuss the importance of human-mediated dispersal in the spread of this invasive species. CONCLUSIONS: Our results illustrate the utility of genomic tools in surveillance programs for tracking dispersal patterns. Such strategies can contribute to mitigating the growing public health threat posed by Ae. aegypti's continued expansion in California, particularly as locally acquired arbovirus cases increase.