Submitted to: Annals of the Entomological Society of America
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/22/2013
Publication Date: 7/31/2013
Citation: Yee, W.L., Chapman, P.S., Sheets, D.H. 2013. Body size and shape analyses of F1 hybrid Rhagoletis pomonella and Rhagoletis zephyria (Diptera: Tephritidae). Annals of the Entomological Society of America. 106:410-423. Interpretive Summary: The apple maggot fly is an important quarantine pest of apples in the Pacific Northwest of the U.S. The snowberry maggot fly is a non-pest but looks almost exactly like apple maggot fly and also hybridizes with it. Methods to identify hybrids would be useful for pest management. Personnel at the Yakima Agricultural Research Laboratory in Wapato, WA and Canisius College in Buffalo, NY determined ways to classify apple maggot fly, snowberry maggot fly, and their hybrids using body shape traits. It was found that 90% of hybrid female flies had novel wing shapes not found in parental flies. Wings of hybrid male flies were less distinctive. Results are important because they suggest wing shape can be used to identify female hybrid flies, thus decreasing the possibility of misidentifying flies caught near apple orchards.
Technical Abstract: Experimentally generated F1 hybrids of apple maggot fly, Rhagoletis pomonella (Walsh), and Rhagoletis zephyria Snow (Diptera: Tephritidae) were classified using morphometric methods. Five of nine mean body size measurements of hybrids from crossing female R. pomonella × male R. zephyria were intermediate between those of non-hybrids, but substantial overlap occurred. Aculeus lengths of hybrid females were intermediate or were more similar to those of R. pomonella than R. zephyria, including in hybrids from the reciprocal cross. Hybrids from the reciprocal cross were rare and too few to use other than for analysis of single body measurements. Based on six or seven size measures, 25.0% of female and 44.4% of male hybrids were correctly classified; misclassified female hybrids resembled R. pomonella; misclassified male hybrids, one or the other parental species. Mean wing shapes of hybrid females based on landmark measurements were novel, whereas those of males were intermediate between those of non-hybrids. Based on wing shapes + natural log (ln) centroid size, 90.9% of female and 66.7% of male hybrids were correctly classified; hybrid females were misclassified as R. pomonella and more hybrid males as R. zephyria. Based on surstylus shape, 27.7% of male hybrids were correctly classified; more were misclassified as R. pomonella. Results show wing shape + ln centroid size is the most useful measure for identifying female and male hybrids and that R. pomonella genes for aculeus length and/or wing shape appear dominant to those of R. zephyria in hybrid females.