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%).
KeywordsWinter moth Bruce spanworm Forest pests Hybrid zone Gene flow Wolbachia
This work would not have been possible without the collaboration of many individuals who collected samples in both Europe and North America. A complete list of all the collectors is provided in Table S1. We would also like to thank D. Newman for laboratory assistance, and R. Crandall, M. Davis, B. Griffin, R. Gwiazdowski, M. Labbé, J. Lombardo, N.J. Mills, T. Murphy, and G.K. Roderick for their creative comments and suggestions throughout this study. Funding for this project was provided by USDA-FS 13-CA-11420004-236 awarded to JSE, 12-USDA-FS JV-11242303-096 awarded to AC. The authors would also like to thank Dr. James Fordyce and two anonymous reviewers who provided edits and suggestions to an earlier version of the manuscript.
JSE directed the research. JSE and GHB coordinated the collection of samples. AC provided laboratory access and oversaw the molecular analyses. JCA, NPH, and HJB collected the molecular data. JCA analyzed the dataset and oversaw manuscript preparation. All authors contributed to the project design and in preparing the manuscript.
Compliance with ethical standards
Conflict of interest
The authors declare no conflicts of interest.
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