Widespread hybridization among native and invasive species of Operophtera moths (Lepidoptera: Geometridae) in Europe and North America

In North America the invasive winter moth (Operopthera brumata) has caused defoliation in forest and fruit crop systems in British Columbia, Nova Scotia, Oregon, and in the northeastern United States (the Northeast). In the Northeast, it was previously shown that hybridization is occurring with a native congener, Bruce spanworm (O. bruceata)-a species that has a broad distribution across much of North America. Whether hybridization among winter moth and Bruce spanworm populations has occurred in all of regions where winter moth established is unknown. One factor that might influence hybridization between these two species is the presence of reproductive manipulating endosymbionts, such a Wolbachia. To determine the geographic extent of hybridization among populations of these two species, we classified 1400 field-collected moths from Europe and North America as either being winter moth, Bruce spanworm, or hybrids using 10-12 polymorphic microsatellite loci. We then screened each individual for the presence of Wolbachia by PCR amplification of the wsp gene fragment. For all hybrids, we determined their maternal species-lineage by PCR amplification and sequencing of the mitochondrial locus cytochrome oxidase I. We find that winter moth x Bruce spanworm hybrid individuals appear to be present in all regions of North America that winter moth has invaded, and that hybrids are of both winter moth and Bruce spanworm maternal-origins. In addition, we find Wolbachia infected individuals from all species in North America, and that winter moth individuals in North America have a much lower infection rate (11.5%) than individuals in Europe (55.1%).