GENE FLOW IN COLONIZING HIPPODAMIA-VARIEGATA LADYBIRD BEETLE POPULATIONS

Genetic diversity and gene flow at allozyme loci was investigated in n atural and laboratory-reared populations of the predatory ladybird spe cies Hippodamia variegata, a recently naturalized beetle from the Pala earctic. Gene diversity was 24.9 +/- 4.9% at 28 resolved loci and 31.6 +/- 5.5% at 22 polymorphic loci, Average gene diversity at nine polym orphic loci was only slightly greater among field-collected beetles th an among laboratory-cultured beetles, There were five alleles in cultu red beetles not found in natural U.S, population samples, Wright's F s tatistics showed modest genetic differentiation among two field collec tions from the northeastern United States and one from Europe (F-ST = 0.107 +/- 0.077), Analysis of variance in gene frequencies in these fe ral ladybirds showed that about 97% of the variance existed within pop ulations of this colonizing species, A substantial level of genetic di fferentiation was detected among 10 laboratory populations descended f rom collections made in Europe, Asia, North Africa, and Chile (F-ST = 0.191 +/- 0.021), Drift is the most likely explanation for this differ entiation.