Gene flow in the exotic colonizing ladybeetle Harmonia axyridis in North America

Gene flow was studied in Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae), an exotic, arboreal lady-beetle predator that recently spread rapidly through-out North America. A survey of isozyme polymorphisms showed 30 of 52 resolved putative loci were polymorphic (58%), and the mean heterozygosity was 16.75 +/- 2.98% among all loci and 26.31 +/- 4.37% at only the polymorphic loci. The mean number of alleles at the 52 loci was 2.01 +/- 1.97. Gene frequencies were estimated in populations from Georgia, Virginia, Delaware, Rhode Island, Arkansas, Illinois, Iowa, and Oregon and differed significantly (P 0.02) at 11 of 16 loci. Three of 16 loci (Fbp, Est-1, Tre) were not in Hardy-Weinberg equilibrium in all populations and are not included in the F statistics. Random mating was indicated within populations (FIS