Abstract Eclosion times and rates of Rhagoletis tabellaria (Fitch) (Diptera: Tephritidae) and its parasitoid wasp Utetes tabellariae (Fischer) (Hymenoptera: Braconidae) held at different chilling durations were determined in the laboratory. Adult fly and wasp longevity were also determined. Adult female and male flies from R. tabellaria puparia chilled for 195 days at 4.8 °C and then held at 23.2 °C eclosed on average earlier than U. tabellariae reared from R. tabellaria puparia. Rhagoletis tabellaria also eclosed significantly earlier from puparia chilled for 150 days than 120 days at 2.7 °C, but U. tabellariae eclosion from the two treatments did not differ significantly. Rhagoletis tabellaria eclosion rates were greater with longer chill durations, but U. tabellariae eclosion rates per R. tabellaria puparium did not differ among chill durations. No R. tabellaria eclosed from nonchilled puparia held at 20–22 °C, but at least 18.8% of nonchilled U. tabellariae eclosed. Female and male R. tabellaria on average survived 52.1 and 83.3 days, respectively, while female and male U. tabellariae survived 37.7 and 28.7 days, respectively. Results indicate diapause and developmental traits of R. tabellaria may be more dependent on chilling durations and less flexible than those of U. tabellariae , a wasp that appears adapted to flies in the R. tabellaria species complex.
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Contrast in Post-Chill Eclosion Time Strategies Between Two Specialist Braconid Wasps (Hymenoptera: Braconidae) Attacking Rhagoletis Flies (Diptera: Tephritidae) in Western North America
Abstract Parasitoids comprise a speciose insect group, 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, whereas Diachasma muliebre (Muesebeck) oviposits into R. indifferens larvae feeding in cherries. Because Rhagoletis only have one major generation a year and the wasps attack temporally distinct fly life stages, we predicted that 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, whereas 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 evolves 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.
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- Award ID(s):
- 1638997
- NSF-PAR ID:
- 10295226
- Editor(s):
- Schilder, Rudolf
- Date Published:
- Journal Name:
- Environmental Entomology
- ISSN:
- 0046-225X
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Schilder, Rudolf (Ed.)Abstract Closely related phytophagous insects that specialize on different host plants may have divergent responses to environmental factors. Rhagoletis pomonella (Walsh) and Rhagoletis zephyria Snow (Diptera: Tephritidae) are sibling, sympatric fly species found in western North America that attack and mate on plants of Rosaceae (~60 taxa) and Caprifoliaceae (three taxa), respectively, likely contributing to partial reproductive isolation. Rhagoletis zephyria evolved from R. pomonella and is native to western North America, whereas R. pomonella was introduced there. Given that key features of the flies’ ecology, breeding compatibility, and evolution differ, we predicted that adult eclosion patterns of the two flies from Washington State, USA are also distinct. When puparia were chilled, eclosion of apple- and black hawthorn-origin R. pomonella was significantly more dispersed, with less pronounced peaks, than of snowberry-origin R. zephyria within sympatric and nonsympatric site comparisons. Percentages of chilled puparia that produced adults were ≥67% for both species. However, when puparia were not chilled, from 13.5 to 21.9% of apple-origin R. pomonella versus only 1.2% to 1.9% of R. zephyria eclosed. The distinct differences in eclosion traits of R. pomonella and R. zephyria could be due to greater genetic variation in R. pomonella, associated with its use of a wider range of host plants than R. zephyria.more » « less
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Studies assessing the predictability of evolution typically focus on short-term adaptation within populations or the repeatability of change among lineages. A missing consideration in speciation research is to determine whether natural selection predictably transforms standing genetic variation within populations into differences between species. Here, we test whether and how host-related selection on diapause timing associates with genome-wide differentiation during ecological speciation by comparing ancestral hawthorn and newly formed apple-infesting host races of Rhagoletis pomonella to their sibling species Rhagoletis mendax that attacks blueberries. The associations of 57 857 single nucleotide polymorphisms in a diapause genome-wide-association study (GWAS) on the hawthorn race strongly predicted the direction and magnitude of genomic divergence among the three fly populations at a field site in Fennville, MI, USA. The apple race and R. mendax show parallel changes in the frequencies of putative inversions on three chromosomes associated with the earlier fruiting times of apples and blueberries compared to hawthorns. A diapause GWAS on R. mendax revealed compensatory changes throughout the genome accounting for the earlier eclosion of blueberry, but not apple flies. Thus, a degree of predictability, although not complete, exists in the genomics of diapause across the ecological speciation continuum in Rhagoletis . The generality of this result is placed in the context of other similar systems. This article is part of the theme issue ‘Towards the completion of speciation: the evolution of reproductive isolation beyond the first barriers'.more » « less
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Abstract An outstanding issue in the study of insect host races concerns the idea of ‘recursive adaptive divergence’, whereby adaptation can occur repeatedly across space and/or time, and the most recent adaptive episode is defined by one or more previously similar cases. The host plant shift of the apple maggot fly,
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1093/ee/nvab080
