Isozyme Variation between Geographic Populations of the Colorado Potato Beetle, Leptinotarsa decemlineata (Coleoptera: Chrysomelidae)1

Abstract

Genetic divergence of 12 populations of the Colorado potato beetle, Leptinotarsa decemlineata(Say), was studied by starch gel electrophoresis to examine enzyme products of 11 genetic loci (ACPH, EST-1, EST-2, FUM, G-6PDH, GOT, α-GPDH, IDH, MDH, ME, and SOD). Mean heterozygosity of these populations was 0.206, with an average proportion of polymorphic loci of 0.515. The 11 populations from the United States and Europe were similar genetically, with an average genetic distance of 0.022 and a fixation index of 0.068. Heterozygosity of the Mexican population was significantly lower than that of the other populations. One locus (SOD) was diagnostic, separating the Mexican population from the others. Average genetic distance between the Mexican population and the other 11 populations was 0.212, indicating that it may be a distinct subspecies. Genetic distance between L. decemlineata and L. haldemani Rogers was 0.439. The moderately high levels of genetic variability found in the Colorado potato beetle suggest that the species is able to exploit a wide range of food plants without further adaptation.