Population genetics of Aedes aegypti (Diptera: Culicidae) in India reveals high connectivity and weak geographic and climatic structuring.

Understanding the genetic structure and diversity of Aedes aegypti (Linnaeus, 1762) populations is critical for predicting transmission dynamics and implementing effective vector control strategies. This study assessed the genetic diversity, population structure, and influence of geography and climate on Ae. aegypti populations across India. Of 308 genotyped individuals, 257 high-quality genotypes from 13 collection sites across 6 climatic regions were retained for analysis using 10 microsatellite loci. High genetic diversity was observed across all populations, consistent with substantial effective population sizes and ongoing gene flow. Moderate but biologically significant genetic differentiation was detected (global FST = 0.077), with the majority of genetic variation occurring within populations (AMOVA: 91.62%). Clustering analyses revealed weak to moderate population structuring, identifying approximately 3 genetic clusters with substantial admixture. Population assignment tests further supported extensive connectivity, with 42% of individuals assigned to nonnative populations. Bottleneck analyses found no recent demographic contractions, and all populations exhibited allele frequency distributions consistent with mutation-drift equilibrium. The Mantel test revealed no significant isolation by distance, suggesting that geographic separation alone does not drive genetic differentiation. Redundancy analysis further indicated that climatic and geographic variables did not significantly explain overall genetic variation, although partial analyses suggested a modest independent contribution of spatial structure. Overall, the genetic structure of Ae. aegypti in India may be influenced by human-mediated dispersal and local ecological processes rather than by broad geographic or climatic constraints. These findings highlight the importance of considering population connectivity in region-specific vector surveillance and control programs.