| Abstrakt: |
The apple maggot fly, Rhagoletis pomonella(Walsh) (Diptera: Tephritidae), was introduced from eastern North America into western North America via infested apples (Malus domesticaBorkhausen) about 44 yr ago, where it subsequently adapted to 2 hawthorn species, Crataegus douglasiiLindley and C. monogynaJacquin. Here, we test whether R. pomonellahas also adapted to large-thorn hawthorn, Crataegus macracanthaLoddiges ex Loudon, in Okanogan County, Washington State, USA. In 2020, 2021, and 2022, fruit of C. macracanthawere shown to ripen in late September and were infested at rates from 0.7% to 3.0%. In laboratory rearing studies, large-thorn hawthorn flies from C. macracanthaeclosed on average 9–19 days later than apple flies from earlier ripening apple (August–early September), consistent with large-thorn hawthorn flies having adapted to the later fruiting phenology of its host. In a laboratory no-choice test, significantly fewer (64.8%) large-thorn hawthorn than apple flies visited apples. In choice tests, greater percentages of large-thorn hawthorn than apple flies resided on and oviposited into C. macracanthaversus apple fruit. Large-thorn hawthorn flies were also smaller in size than apple flies. Our results provide further support for the recursive adaptation hypothesis that R. pomonellahas rapidly and independently specialized phenologically and behaviorally to different novel hawthorn hosts since its introduction into the Pacific Northwest of the USA, potentially leading to host race formation. |
