Genetic structure of Aedes aegypti populations in Thailand using mitochondrial DNA.

A hierarchical population genetic study was conducted among 19 Aedes aegypti populations in Thailand from Chiang Mai in the north to Songkhla province in the south. Single-strand conformation polymorphism analysis was used to examine variation in a 359-basepair region of the NADH dehydrogenase subunit 4 mitochondrial DNA gene (ND4). Seven haplotypes were detected in two lineages previously identified in ND4 haplotypes from North America. Gene flow estimates and highly significant variation among populations within 25 kilometers implicated genetic drift and vector control efforts as major factors in genetic structure. Mantel regression analysis demonstrated no isolation by distance. Urban areas were relatively panmictic, while suburban/rural sites exhibited more restricted gene flow. Significant genetic structure among groups of collections > 100 kilometers apart is consistent with recent (approximately 50 year) expansion of Ae. aegypti from highly populated areas accompanied by founder effects, but could also reflect the overall low genetic diversity in ND4 in Thailand.