Allozyme Differences between Heliothis virescens and H. zea

A field population of Heliothis virescens (F.) is compared with both field and laboratory populations of H. zea (Boddie) with respect to genetic variation at 19 enzyme loci. Nei‗s standard genetic distance between field populations of the 2 species is 0.874. Tetrazolium Oxidase-A and Tetrazolium Oxidase-B are diagnostic loci with complete discrimination between the 2 species. Eight other loci discriminate with 99% to 95% probability. The mean heterozygosity for H. zea and H. virescens is higher than most non-pest invertebrates even though ca. 50% group I enzyme loci were used. The laboratory population of H. zea shows a 14.3% reduction in polymorphic loci and 23.8% of the loci examined were significantly different (a>.005) between laboratory and field populations. These genetic changes are consistent with genetic drift in a small isolated population. The genetic differentiation of laboratory stocks should be considered when using laboratory reared insects in field situations.