Abstract
The adaptation of phytophagous insects to different host plants can lead to prezygotic isolation and potentially promote speciation. A textbook example of ecological adaptation and speciation in the face of gene flow is the apple maggot Rhagoletis pomonella. Naturally infesting hawthorn, a population shifted to the newly introduced domesticated apples. This led to the formation of ecologically and genetically differentiated host forms. Apples tend to fruit about three weeks earlier than hawthorns and therefore the difference in fruiting time resulted in allochronic prezygotic isolation initiating speciation. Similar to its famous congener, Rhagoletis cerasi is a univoltine insect that has adapted to cherries (Prunus sp.) and honeysuckle (Lonicera sp.). In central Europe Prunus fruits 2–3 weeks earlier than Lonicera. The different phenology of their hosts might act as a prezygotic isolation barrier. However, genetic as well as ecological studies did not find a clear differentiation between the two host forms. Here we determine if the eclosing time of the two host forms of R. cerasi differ according to the phenology of their host. Further we study the lifespan of adult flies to understand if phenological adaptation to the different hosts might be responsible for allochronic isolation between Prunus and Lonicera infesting R. cerasi