Mitochondrial COI gene based population genetic structure and diversity of Aedes aegypti populations across diverse climatic regions of India.

Aedes aegypti, the primary vector of dengue, chikungunya, Zika, and yellow fever, shows high ecological plasticity across India, yet its population genetic structure remains poorly understood. This study investigates the genetic diversity and spatial differentiation of Ae. aegypti from 13 geographically and climatically diverse regions of India using partial mitochondrial cytochrome oxidase I (COI) gene sequences. A total of 126 individuals revealed 21 haplotypes, with moderate haplotype diversity (mean Hd = 0.55) and low nucleotide diversity (mean π = 0.00663), suggesting recent common ancestry and limited sequence divergence. A dominant haplotype (Hap_2), shared across all populations in a star-like haplotype network, indicates a widespread ancestral lineage with signs of recent expansion. However, the presence of region-specific haplotypes indicates localized differentiation. Genetic differentiation was significant in certain population pairs, particularly involving Itanagar, Kota, and Thiruvananthapuram, with FST values as high as 0.5262. Principal Coordinates Analysis (PCoA) and SAMOVA supported moderate structuring, while AMOVA showed no significant differentiation based on climatic zones. Redundancy analysis and Mantel tests highlighted that geographic distance explained more genetic variation than climate, although only one spatial variable (geo2) emerged as statistically significant. These findings highlight the dominant role of spatial factors, likely reflecting dispersal barriers or limited gene flow, in shaping population structure. Understanding this heterogeneity is vital, as genetic differentiation may influence vector competence, adaptation potential, and the emergence of insecticide resistance. This study provides baseline genetic insights essential for region-specific vector surveillance and control strategies across India's diverse eco-climatic landscape.