Limited genetic evidence for host plant-related differentiation in the western cherry fruit ¿y, Rhagoletis indifferens

Authors: ST JEAN, GILBERT - University Of Notre Dame; HOOD, GLEN - Rice University; EGAN, SCOTT - Rice University; POWELL, THOMAS - University Of Florida; SCHULER, HANNES - University Of Notre Dame; DOELLMAN, MEREDITH - University Of Notre Dame; GLOVER, MARY - University Of Notre Dame; SMITH, JAMES - Michigan State University; Yee, Wee; GOUGHNOUR, ROBERT - Washington State University; RULL, JUAN - Institute De Ecologia - Mexico; ALUJA, MARTIN - Institute De Ecologia - Mexico; FEDER, JEFFEREY - University Of Notre Dame

Submitted to: Entomologia Experimentalis et Applicata
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/1/2018
Publication Date: 8/29/2018
Citation: St Jean, G., Hood, G., Egan, S., Powell, T., Schuler, H., Doellman, M., Glover, M., Smith, J., Yee, W.L., Goughnour, R., Rull, J., Aluja, M., Feder, J. 2018. Limited genetic evidence for host plant-related differentiation in the western cherry fruit ¿y, Rhagoletis indifferens. Entomologia Experimentalis et Applicata. 166(9):739-751. https://doi.org/10.1111/eea.12712.
DOI: https://doi.org/10.1111/eea.12712

Interpretive Summary: The cherry fruit fruit fly is a threat to the commercial cherry industry in the western U.S., with populations attacking cultivated and wild cherries. The shift from wild to cultivated cherries may have caused flies to diverge genetically, so that flies on wild cherry are a lower threat to cultivated cherries. Personnel at the University of Notre Dame, Notre Dame, IN, Rice University, Houston, TX, University of Florida, Gainesville, FL, Michigan State University, E. Lansing, MI, USDA-ARS, Wapato, WA, Washington State University, Vancouver, WA, and the Instituto de Ecología, Veracruz, México compared the genetics of cherry fruit fly populations on wild and cultivated cherries using microsatellites. We found little evidence for microsatellite differentiation between wild cherry versus cultivated cherry populations of flies and that there is no host-related differentiation for flies infesting the two host plants. Results are important in that they suggest flies from wild cherries can be a threat to commercial, cultivated cherries.

Technical Abstract: The shift of the fruit fly Rhagoletis pomonella (Walsh) in the mid-1800s from downy hawthorn, Crataegus mollis (Torrey & Asa Gray) Scheele, to introduced domesticated apple, Malus domestica (Borkhausen) in the eastern U.S. is a model for ecological divergence with gene flow. A similar system may exist in the northwestern U.S. and Canada, where R. indifferens (Curran) is native to the bitter cherry Prunus emarginata (Douglas ex Hooker) Eaton. Populations of R. indifferens shifted and became economic pests on domesticated sweet cherry, Prunus avium (L.) L., shortly after sweet cherries were introduced to the region in the mid-1800s. The fruiting phenology of the two cherries differ in a similar manner as apples and hawthorns, with sweet cherries typically ripening from June to July and bitter cherries from July to August. Here, we report, however, little evidence for microsatellite differentiation between bitter versus sweet cherry populations of R. indifferens or for a genetic association with adult eclosion time, as has been documented for apple and downy hawthorn flies. The findings were similar to previous more limited surveys of R. indifferens in the province of British Columbia, Canada and R. cingulata in the state of Michigan, U.S., suggesting a lack of host-related differentiation for flies infesting different cherry host plants. Possible causes for why host races are readily genetically detected for R. pomonella but not for R. indifferens are discussed.