European corn borer (Ostrinia nubilalis) pheromone-race hybrids: frequency, gene flow and host plant use in the Northeastern US

In the northeastern US, sympatric populations of E and Z pheromone races of European corn borer (Ostrinia nubilalis) are partly reproductively isolated by their pheromone communication system. Hybridization occurs in the field but has been thought to be a relatively rare event. In our study, we used newly developed molecular markers to phenotype the race of O. nubilalis adults captured in several locations in New York and Pennsylvania, and detected a much higher number of hybrids than expected. Analyses of neutral genetic markers indicate significant genetic connectivity of hybrids with both E and Z race populations. Carbon-isotope analysis showed that utilization of non-corn hosts is more frequent in E race than Z race, and that non-corn host-use by hybrids is similar to that of the E race. Our results have implications for the spread of local adaptations (such as resistance to transgenic Bt corn) that evolve in one race to the other. They also have implications for interpretation of trap data baited with E or Z pheromone lures in regions where the two races are sympatric.