Obolodiplosis robiniae is native to North America and is an important introduced insect pest that forms leaf margin roll galls on species of genus Robinia (Fabaceae) in China. It was first detected in China in 2004, but subsequently spread and provoked local outbreaks. An analysis of a 676-bp sequence of the mitochondrial DNA cytochrome oxidase subunit I was conducted in 560 individuals from 28 populations, in order to (1) assess population genetic structuring and (2) explore possible explanations for the rapid spread and invasion success of O. robiniae. Yet, only four haplotypes were identified and the nucleotide diversity was low (π = 0.00005) and among the 560 specimens studied, only ten showed haplotypic variation involving no more than three substitutions. The result showed a low degree of genetic diversity among populations of the successful invasive gall midge, which suggested that the pest experienced a severe genetic bottleneck and a loss of genetic diversity after its introduction. The successful establishment and spread of O. robiniae in China is attributed to the wide distribution of its host plant, thus allowing ample opportunities for gene flow in the pest species, and to the advantageous life history characteristics of O. robiniae.
Microsatellite markers were developed for epidemiological studies on the black locust gall midge Obolodiplosis robiniae (Haldeman) (Diptera: Cecidomyiidae), a native North America pest introduced to Europe and Asia. Polymorphism at each locus was tested on 68 individuals from six populations reared from infected host leaves of Robinia pseudoacacia L. collected in China. Fourteen loci were found to be polymorphic, with the number of alleles ranging from 3 to 10. The observed heterozygosity varied evenly from 0.2667 to 0.6540. For populations, the observed heterozygosity ranged from 0.1429 to 1.000. The allele frequency of the predominant allele varied from 0.250 to 0.500. All loci with negative FST values indicated heterozygote excess in each locus with six populations. Of 14 loci, four were observed to have FST values up to 0.05, which indicated negligible genetic differentiation within the population. Significant deviations (P < 0.05) from the expected Hardy–Weinberg equilibrium, as evaluated using the Markov chain algorithm for each locus and for all six populations, were observed, and genotypic linkage disequilibrium was clearly detected. These markers represent a useful tool to design strategies for integrated pest management and in the study of population evolution in this important introduced pest.
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