Updating the phylogeny of Rhagoletis: focus on relationships of the North American species groups

Flies in the genus Rhagoletis (Diptera: Tephritidae) are economically important fruit pests, and also serve as models for studying modes of speciation and coevolutionary relationships with their braconid (egg, larval) and diapriid (pupal) parasitoids. Bush’s (1966) seminal taxonomic work placed most North American (NA) Rhagoletis species into five species groups (pomonella, tabellaria, cingulata, suavis, and ribicola). Despite several subsequent analyses based on morphology, allozymes, and mitochondrial DNA, the phylogenetic relationships of these five species groups remain unresolved. In addition, it remains unclear whether these (NA) Rhagoletis taxa represent a monophyletic group. Thus, the main goal of this project was to determine the phylogenetic relationships of North American Rhagoletis species. Our approach was a phylogenetic analysis incorporating DNA sequences of COI (mtDNA), 28S (nuclear ribosomal) and CAD (nuclear protein coding) genes. The analysis the combined dataset places the five NA species groups in a well-supported clade with R. batava as sister to the five NA species groups, while placing R. flavigenualis sister to R. juniperina, and R. fausta basal to the entire group.  The close relationship of R. flavigenualis and R. batava to the NA species is interesting because they infest species that have closely related Nearctic counterparts (Juniperus spp and Elaeagnaceae respectively).  These results have interesting implications for the divergence of ancestral Rhagoletis and the formation of extant Nearctic and Palearctic taxa. As a whole, this research will be useful for using the Rhagoletis system to test biogeographic and coevolutionary hypotheses.