The population genetics of the apple maggot fly, Rhagoletis pomonellaand the snowberry maggot, R. zephyria: implications for models of sympatric speciation

True fruit flies belonging to the Rhagoletis pomonella(Diptera:Tephritidae) sibling species complex possess several attributes consistent with a history of sympatric divergence via host plant shifts. Here, we investigate whether hybridization and genetic introgression is occurring between two members of the group, Rhagoletis pomonella(Walsh), whose primary hosts are domestic apples (Malus pumila) and hawthorns (Crataegusspp., and R. zephyria(Snow) whose host is snowberries (Symphoricarposspp.). These flies are important because they appear to be at a transition stage between taxa reproductively isolated solely on the basis of host plant‐related adaptations and those that have evolved additional non‐host dependent sterility and inviability. Observing extensive hybridization and introgression between R. pomonellaand R. zephyriawould have major repercussions for current models of sympatric speciation.