Temporal variation in genetic structure of a colonising species: Aedes albopictus in the United States.

The medically important mosquito, Aedes albopictus, has recently become established in several locations within the United States. A three-year survey of temporal variation in allele frequencies at ten enzymatic loci in 17 populations was undertaken to determine the extent and direction of change since the colonization event. Significant, but non-directional, changes were detected in allele frequencies at most of the loci in all populations. Some alleles detected at low frequencies in earlier samples were not found in subsequent samples. Variance of allele frequencies remained unchanged. In at least two locations, there was an increase in mean heterozygosity, perhaps because of gene flow. There was no significant change in the levels of genetic variation within and among populations. The results from this study indicate that the breeding structure of Ae. albopictus in the U.S. did not differ substantially from that in a native habitat, either soon after colonisation or after several generations in the new habitat. We suggest that a large founder population, gene flow and a rapid population expansion could explain the present breeding structure of Ae. albopictus.