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Frequency of hybridization between Ostrinia nubilalis E-and Z-pheromone races in regions of sympatry within the United States
Ecology and Evolution
  • Brad S. Coates, Iowa State University
  • Holly Johnson, University of Delaware
  • Kyung-Seok Kim, United States Department of Agriculture
  • Richard L. Hellmich, Iowa State University
  • Craig A. Abel, Iowa State University
  • Charles Mason, University of Delaware
  • Thomas W. Sappington, Iowa State University
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Female European corn borer, Ostrinia nubilalis, produce and males respond to sex pheromone blends with either E- or Z-Δ11-tetradecenyl acetate as the major component. E- and Z-race populations are sympatric in the Eastern United States, Southeastern Canada, and the Mediterranean region of Europe. The E- and Z-pheromone races of O. nubilalis are models for incipient species formation, but hybridization frequencies within natural populations remain obscure due to lack of a high-throughput phenotyping method. Lassance et al. previously identified a pheromone gland-expressed fatty-acyl reductase gene (pgfar) that controls the ratio of Δ11-tetradecenyl acetate stereoisomers. We identified three single nucleotide polymorphism (SNP) markers within pgfar that are differentially fixed between E- and Z-race females, and that are ≥98.2% correlated with female pheromone ratios measured by gas chromatography. Genotypic data from locations in the United States demonstrated that pgfar-z alleles were fixed within historically allopatric Z-pheromone race populations in the Midwest, and that hybrid frequency ranged from 0.00 to 0.42 within 11 sympatric sites where the two races co-occur in the Eastern United States (mean hybridization frequency or heterozygosity (HO) = 0.226 ± 0.279). Estimates of hybridization between the E- and Z-races are important for understanding the dynamics involved in maintaining race integrity, and are consistent with previous estimates of low levels of genetic divergence between E- and Z-races and the presence of weak prezygotic mating barriers.

This article is from Ecology and Evolution 3 (2013): 2459–2470, doi:10.1002/ece3.639.

This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
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Brad S. Coates, Holly Johnson, Kyung-Seok Kim, Richard L. Hellmich, et al.. "Frequency of hybridization between Ostrinia nubilalis E-and Z-pheromone races in regions of sympatry within the United States" Ecology and Evolution Vol. 3 Iss. 8 (2013) p. 2459 - 2470
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