Aedes (Finlaya) japonicus (Diptera : Culicidae), a newly recognized mosquito in the United States: Analyses of genetic variation in the United Statesand putative source populations

Introduction of potential disease vectors into a new geographic area poses health risks to local human, livestock, and wildlife populations. It is the refore important to gain understanding of the dynamics of these invasions, in particular its sources, modes of spread after the introduction, and vect orial potential. We studied the population genetics of Aedes (Finlaya) japo nicus japonicus (Theobald), an Asian mosquito that was recognized for the f irst time in the United States in 1998. We examined patterns of genetic div ersity using random amplified polymorphic DNA and sequences of ND4 of mtDNA by comparing samples from populations spanning the range of this mosquito in Japan (six samples) and the United States (nine samples) as well as spec imens intercepted in New Zealand in 1999. We found geographically different iated populations in Japan, indicating limited gene now even on small spati al scales. In the United States, we found evidence of significant genetic d ifferentiation between samples from New York, Connecticut, and New Jersey a nd those from mid-Pennsylvania and Maryland. We were unable to pinpoint the source location(s) in Japan, although some of the U.S, samples are genetic ally close to samples from south Honshu and western Kyushu. Further studies should include samples from Korean populations. Distinct genetic signature s in U.S. populations undergoing expansion suggest the possibility of local increases in genetic diversity if and where they meet.