Contrast in post-chill eclosion time strategies between two specialist braconid wasps (Hymenoptera: Braconidae) attacking rhagoletis flies (Diptera: Tephritidae) in western North America

Authors: Yee, Wee; FORBES, A - University Of Iowa; FEDER, J - University Of Notre Dame

Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/16/2021
Publication Date: 8/13/2021
Citation: Yee, W.L., Forbes, A.A., Feder, J.L. 2021. Contrast in post-chill eclosion time strategies between two specialist braconid wasps (Hymenoptera: Braconidae) attacking rhagoletis flies (Diptera: Tephritidae) in western North America. Environmental Entomology. 50(5):1173-1186. https://doi.org/10.1093/ee/nvab080.
DOI: https://doi.org/10.1093/ee/nvab080

Interpretive Summary: Natural enemies of pest insects display a wide array of life history strategies but those of many fruit fly species remain largely unknown. Personnel at the USDA laboratory in Wapato, WA, University of Notre Dame, IN, and University of Iowa determined the relationships between emergence times of adult western cherry fruit and a fly attacking dogwood fruit and their respective wasp parasites. The flies are attacked by wasps at different life stages; the wasp of cherry fruit fly attacks larvae while the wasp of the dogwood fly attacks eggs. It was found that the wasp attacking dogwood fly emerged soon after its host fly emerged while the wasp attacking cherry fruit fly emerged much later than its host fly, to match the presence of the fly stage attacked. Results are important for understanding how different parasites have become highly specialized to exploit specific fruit flies

Technical Abstract: Parasitoids comprise one of the most speciose groups of insects, displaying a wide array of life history strategies. In the Pacific Northwest of the United States, the tephritid fruit flies Rhagoletis tabellaria (Fitch) and Rhagoletis indifferens Curran infest red osier dogwood, Cornus sericea L. (Cornaceae), and bitter cherry, Prunus emarginata (Douglas ex Hooker) Eaton (Rosaceae), respectively. The flies are parasitized by different braconid wasps at different life stages; Utetes tabellariae (Fischer) oviposits into R. tabellaria eggs, while Diachasma muliebre (Muesebeck) oviposits into R. indifferens larvae feeding in cherries. Because Rhagoletis are univoltine and the wasps attack temporally distinct fly life stages, we predicted that the eclosion times of U. tabellariae should more closely follow that of its host than the larval-attacking D. muliebre. As predicted, U. tabellariae eclosed on average 6.0–12.5 d later than R. tabellaria, while D. muliebre eclosed on average 32.1 d after R. indifferens. Unexpectedly, however, longer chill duration differentially affected the systems; longer overwinters minimally influenced eclosion times of R. tabellaria and U. tabellariae but caused earlier eclosion of both R. indifferens and D. muliebre. Results imply that in temperate regions, diapause timing in braconid wasps evolve in response to both host life stage attacked and fly eclosion characteristics, possibly reflecting differential effects of winter on host plant fruiting phenology. Differences in phenological sensitivity of the lower host plant trophic level to variation in environmental conditions may have cascading effects, sequentially and differentially affecting eclosion times in higher frugivore (fly) and parasitoid (wasp) trophic levels