Genetic characterization of Aedes aegypti (Diptera: Culicidae) mosquitoes from Rio Grande do Sul, the southernmost state of Brazil, based on the mitochondrial COI gene

ABSTRACT Aedes aegypti is a major public health concern worldwide due to its role as a vector of arboviral diseases, particularly dengue. In the Brazilian state of Rio Grande do Sul, the presence of this mosquito has expanded to nearly all municipalities. This study provides the first data on the molecular characterization and phylogenetic analysis of Ae. aegypti larvae collected from 26 localities across Rio Grande do Sul. Using the mitochondrial Cytochrome Oxidase subunit I (COI) gene, 402 sequences of 658 bp were analyzed. In total, 43 haplotypes were identified, revealing high haplotype diversity (Hd = 0.7556) and low nucleotide diversity (π = 0.00570). Neutrality tests (Fu’s Fs) indicated population expansion. Pairwise genetic differentiation (FST) ranged from moderate (0.08957) to very high (0.97233). Molecular variance analysis indicated that the most variation occurred within populations (74.02%). No isolation based on distance was detected. Phylogenetic analysis suggested the presence of two genetic lineages and multiple introductions. These findings offer critical insights for vector surveillance, emphasizing the importance of integrating genetic monitoring into public health strategies for dengue prevention in Rio Grande do Sul.