GENE FLOW AND DIVERSITY AT ALLOZYME LOCI IN THE 2-SPOTTED LADY BEETLE(COLEOPTERA, COCCINELLIDAE)

High levels of genetic variation in biological control agents are thou ght to be necessary to ensure their successful establishment and geogr aphical spread. Gene diversity was studied in F-2 twospotted lady beet le, Adalia bipunctata (L.), descended from specimens collected in Uzbe kistan and from beetles collected in Oregon, Iowa, and Lake Michigan a t Chicago, IL. Twenty-four of 39 resolved putative loci were polymorph ic and the mean observed heterozygosity was 22.7 +/- 4.4% at the polym orphic loci. The average expected heterozygosity was 24.7 +/- 4.9% at the polymorphic loci and 15.2 +/- 3.3% at all loci. The mean number of alleles at the 39 loci was 1.9 +/- 1.0, and the mean effective number of alleles was 1.3 +/- 0.5. These are substantial levels of diversity . Significant departures from random mating were detected with (F-IS = 0.068 +/- 0.042) and among (F-ST = 0.070 +/- 0.012) the North America n populations but matings were random within populations when problema tic loci were excluded. Analysis of gene frequencies at 5 loci in 4 Br itish and a French population showed the same magnitude of gene flow a s the 3 North American populations. The fixation index between Iowa an d Uzbekistan ladybirds was F-ST = 0.428 +/- 0.128. Our data do not sup port an Old World origin for North American A. bipunctata in historica l times.