Low genetic diversity of Aedes albopictus (Diptera: Culicidae) in El Salvador based on mitochondrial COI sequences: evidence of a well-preserved ancestral lineage in the Americas.

Aedes albopictus (Skuse) is an invasive mosquito species which has rapidly expanded across the Americas since the 1980s. This species has significant implications for public health. This study aimed to assess the genetic diversity and potential invasion routes of Ae. albopictus populations in El Salvador and throughout the Americas using the mitochondrial DNA (mtDNA) CO1 barcode. The mtDNA CO1 was sequenced from 52 samples from 5 departments in El Salvador. Analyses included the El Salvador populations, and an additional 205 GenBank sequences from the American continent and Asia, the region of origin. Haplotype and nucleotide diversity assessments, genetic differentiation, and phylogenetic clustering were performed. Genetic diversity in populations of Ae. albopictus from El Salvador and from most countries in America was generally low; El Salvador had 3 haplotypes. One exception was Colombia, where 12 haplotypes were detected. In the Americas, 22 haplotypes were found overall. Phylogenetic analyses grouped American samples into 2 major clusters, 1 centered around haplotype 19, which was the most abundant and widely distributed. El Salvador shared 2 haplotypes with North America. Ae. albopictus from Puerto Rico was genetically distinct from other groups and grouped together with Asian samples. The Asian outgroups were more diverse than samples from America. The analysis highlighted the presence of ancestral lineages in El Salvador and their role in early and complex colonization patterns of this species across the Americas, providing critical data for future management and control strategies against this invasive vector.