Comparison of isozyme patterns of Aedes aegypti populations collected frompre- and post-Bacillus thuringiensis israelensis treatment sites in Thailand

Isozyme patterns of 13 field-collected populations of Aedes aegypti from Th ailand were compared using starch gel electrophoresis. Three populations we re collected before the Bacillus thuringiensis var. israelensis, (B.t.i.) a pplication was initiated. The other 10 populations were collected after the B.t.i. treatment. Results revealed that the number of polymorphic loci wer e lower in the B.t.i. treated populations as compared to controls. In addit ion, lower genetic variability was found in populations collected from B.t. i. treated sites (Mae Ka Sa [KS] and Mae Kud Luang [KL] village). These res ults are most likely due to a genetic bottleneck produced by the B.t.i. tre atment. Heterozygosity increased in the months following B.t.i. treatment, probably because of immigration when the control program was withdrawn. How ever, the anticipated reduction in the expected heterozygosity was only obs erved in the KS site. This may be due to preexisting low heterozygosity in the KL population. No fixed differences in alleles were detected among the 13 populations.