A survey of genetic variation using allozymes was conducted on 57 populations of Aedes albopictus, an Asian mosquito that was introduced into the US and Brazil in the mid-1980s. Our objective was to quantify the patterns of genetic variation among its populations and to use that information to trace genetically the geographic origin of the US and Brazilian populations. Populations from the various regions were genetically distinct from one another. Populations from within a region were genetically similar to one another, which resulted in a significant positive correlation between geographic and genetic distances. A discriminant analysis of allele frequencies separated populations from the various countries into nine non-overlapping clusters; the US, Japanese, Chinese and Brazilian populations formed closely placed, but distinct, clusters. The probability of assigning a population to the correct country was 98 per cent. The US and the Brazilian populations were closest in terms of genetic distance from the Japanese populations. Based on discriminant and genetic distance analyses, we conclude that the US and the Brazilian Aedes albopictus originated in Japan.
