Biological and genetic differences between populations of diamondback moth from different geographic origins

The diamondback moth, Plutella xylostella (Lepidoptera: Yponomeutidae), is a major pest of Brassicaceae and has a worldwide distribution. Biological and genetic differences were studied between populations native to South Africa, Benin, Brazil, France, Japan, United States, Martinique, Réunion Island, Uzbekistan and five localities in Australia. To observe the variability of oviposition behaviour between populations, the eggs laid by 20 females from each population studied were counted daily. Females from Benin and South Africa laid more eggs than the females from Uzbekistan and Martinique. Oviposition duration is longest (30 days) in the Uzbekistan population and varies from 15 to 20 days in the other populations. Females from Benin, Réunion Island and Martinique laid the majority of their eggs in the first four days; those from Uzbekistan and South Africa staggered oviposition over the whole period. Concerning genetic differences, the results of isoenzyme electrophoresis reveal variability between populations for nine loci. Tests of the Hardy-Weinberg equilibrium show heterozygote deficits in many populations. Analysis of allelic frequencies gives an estimate of Fst of 0.103 for all the populations studied. The populations from Australia and Japan are the most different from other populations and from each other. Some biological and genetic differences are shown between populations. Genetic differences are not correlated with the geographic distance separating the populations.