|ARCELLA, TRACY - University Of Notre Dame|
|SIM, SHEINA - University Of Notre Dame|
|HOOD, GLEN - University Of Notre Dame|
|POWELL, THOMAS - University Of Florida|
|SCHWARZ, DIETMAR - Western Washington University|
|EGAN, SCOTT - University Of Notre Dame|
|GOUGHNOUR, ROBERT - Washington State University|
|SMITH, JAMES - Michigan State University|
|FEDER, JEFF - University Of Notre Dame|
Submitted to: Evolutionary Applications
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/8/2015
Publication Date: 9/1/2015
Citation: Arcella, T., Sim, S., Yee, W.L., Hood, G., Powell, T., Schwarz, D., Egan, S., Goughnour, R., Smith, J., Feder, J. 2015. Hybridization and the spread of the apple maggot fly, Rhagoletis pomonella (Diptera: Tephritidae), in the Northwestern United States. Evolutionary Applications. 8(8):834-846.
Interpretive Summary: The apple maggot fly is a major quarantine pest of commercial apple in the Pacific Northwest of the U.S. Hybridization could be an important process enabling apple maggot to shift to new host plant and evolve to become new economic pests. Personnel at the USDA-ARS Yakima Agricultural Research Laboratory in Wapato, WA, University of Notre Dame, IN, USDA-ARS in Hilo, HI, University of Florida in Gainesville, and Western Washington University in Bellingham, WA determined whether hybridization between the native snowberry maggot and introduced apple maggot is occurring and whether this may be aiding the spread of apple maggot into the commercial apple-growing regions of central Washington state. Results implied hybridization between the species occurs at a rate of 1.1% per generation but there was no evidence for increased hybridization in central Washington. Results suggest hybridization is not a factor of importance in central Washington, and thus not of concern in enabling further host shift and host breadth.
Technical Abstract: Hybridization could be an important process interjecting variation into insect populations enabling host plant shifts and the origin of new economic pests. Here, we examine whether hybridization between the native snowberry-infesting fruit fly Rhagoletis zephyria (Snow) and the introduced quarantine pest R. pomonella (Walsh) is occurring and may aid the spread of the latter into more arid commercial apple growing regions of central Washington state, U.S.A. Results for 19 microsatellites implied hybridization occurring at a rate of 1.1% per generation between the species. However, there was no evidence for increased hybridization in central Washington. Allele frequencies for seven microsatellites in R. pomonella were more “R. zephyria-like” in central Washington, suggesting that genes conferring resistance to desiccation may be adaptively introgressing from R. zephyria. However, in only one of these cases was the putatively introgressing allele from R. zephyria not found in R. pomonella in the eastern U.S.A. Thus, many of the alleles changing in frequency may have been prestanding in the introduced R. pomonella population. The dynamics of hybridization are therefore complex and nuanced for R. pomonella, with various causes and factors, including introgression for a portion, but not all of the genome, potentially contributing to the pest insect’s spread.