Biological invasions represent a major threat to agriculture and forestry across the globe. Thaumastocoris peregrinus is a small sap-sucking heteropteran bug that has recently invaded a number of eucalypt plantations worldwide from its native range in Australia. To date, no studies have examined the range of this insect within Australia, and its population genetics remain poorly understood. We sampled T. peregrinus from 16 populations from South East Queensland, across New South Wales (NSW) and Victoria to south-eastern South Australia, and generated microsatellite and mtDNA data for ~ 200 individuals. Population genetic analyses consistently revealed moderate levels of genetic isolation by distance among populations across the range. Nonetheless, T. peregrinus has undergone dispersal across large distances, as revealed by the presence of identical mitochondrial haplotypes in both South East Queensland and South Australia. Two populations within the Sydney area (NSW) were divergent from other populations based on STRUCTURE and factorial correspondence analysis. They also had relatively low allelic richness and haplotype diversity indices. These results suggest they are the result of a relatively recent invasion event, consistent with their discovery in 2001. Pairwise genetic distance analyses suggest that the source of the invasion may have been central NSW. Our study provides an important framework for understanding the biology of this pest in its native environment, and may have implications for determining how it has invaded multiple areas worldwide.
