Gene Flow in the Exotic Colonizing LadybeetleHarmonia axyridisin North America

Abstract

Gene flow was studied inHarmonia axyridis(Pallas) (Coleoptera: Coccinellidae), an exotic, arboreal ladybeetle predator that recently spread rapidly throughout 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, Tre) were not in Hardy-Weinberg equilibrium in all populations and are not included in theFstatistics. Random mating was indicated within populations (FIS = −0.005 ± 0.014) but not among populations (FST = 0.025 ± 0.005). According to Wright's island model,FSTestimates the average number of reproducing immigrants to be equivalent to ca. 10 beetles per population per generation. Thus there was a measure of genetic differentiation caused by drift, but this differentiation was small with respect to the large geographical distances among the sampled populations. The genetic data suggest that the founding North American population(s) was substanti KeywordsHarmonia axyridis, isozyme variation, breeding structure, gene flow, colonizing species Gene flow was studied in Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae), an exotic, arboreal ladybeetle predator that recently spread rapidly throughout North America. A survey of isozyme polymorphisms showed 30 of 52 resolved putative loci were polymorphic (58%), and the mean heterozygosity was 16.75 6 2.98% among all loci and 26.31 6 4.37% at only the polymorphic loci. The mean number of alleles at the 52 loci was 2.01 6 1.97. Gene frequencies were estimated in populations from Georgia, Virginia, Delaware, Rhode Island, Arkansas, Illinois, Iowa, and Oregon and differed significantly (P F 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 (F IS 5 20.005 6 0.014) but not among populations (F ST 5 0.025 6 0.005). According to Wright's island model, F ST estimates the average number of reproducing immigrants to be equivalent to ca. 10 beetles per population per generation. Thus there was a measure of genetic differentiation caused by drift, but this differentiation was small with respect to the large geographical distances among the sampled populations. The genetic data suggest that the founding North American population(s) was substantial. r 1997 Academic Press

Invasions by Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae) in the Western Hemisphere: implications for South America

“…We conjecture that the arrival of H. axyridis in Oregon in 1991 resulted from accidental or intentional releases, not from its unaided dispersal from the southeastern U.S.A. For instance, this predator was commercially available as a biological control agent in North America (Heimpel & Lundgren 2000) and was intentionally redistributed within the continent for biological control purposes, with well documented intentional movement of H. axyridis from the southeastern U.S.A. to California and New Mexico, U.S.A in 1992 and 1993 and Texas, U.S.A. in 1994 (Tedders & Schaefer 1994). It is interesting to note that the extensive spread of H. axyridis in North America has occurred despite relatively narrow genetic differentiation of the invading populations (Krafsur et al 1997).…”

“…the succinea group appears to predominate throughout North America (Chapin & Brou 1991;Tedders & Schaefer 1994;Dreistadt et al 1995;Kidd et al 1995;LaMana & Miller 1996;Hesler et al 2001Hesler et al , 2004Wise et al 2001) even though initial colonies of this insect maintained by the United States Department of Agriculture contained the succinea and melanic groups (Krafsur et al 1997) and both groups were available commercially (e.g., Koch et al 2004b).…”

Comparative genetic studies of native and introduced Coccinellidae in North America

“…In 1988 and 1991, the first detections of H. axyridis were made in Louisiana and Georgia, hundreds of kilometers from their release sites (Chapin & Brou, 1991;Tedders & Schaefer, 1994). Thereafter, H. axyridis rapidly spread in North America and is now found throughout the United States and Canada (Coderre et al, 1995;Dreistadt et al, 1995;LaMana & Miller, 1996;Nalepa et al, 1996;Krafsur et al, 1997).…”

“…We estimated genetic diversities and gene flow in the foregoing Palearctic species (Krafsur & Obrycki, 1996;Krafsur et al, 1992Krafsur et al, , 1996aKrafsur et al, , 1997. In addition, we quantified genetic diversity in the ladybird species, Adalia bipunctata L. and Coleomegilla maculata Degeer (Krafsur et al, , 1996b, and added diversity esti-mates for the Neotropical Eriopis connexa Germar and the Palearctic Scymnus frontalis (F.) coccinellids.…”

Harmonia axyridis in Europe: spread and distribution of a non-native coccinellid

“…Despite releases in fourteen US states 45 between 1964and 1982(Gordon 1985, H. axyridis was not reported as established in the 46 country until 1988 (Chapin and Brou 1991). There is uncertainty over the source of the 47 established US population, which may originate from a single intentional release or 48 accidental introduction (Krafsur et al 1997). Day et al (1994) suggested that the source 49 could have been accidental seaport introductions.…”