title: Allopatric genetic origins for sympatric host-plant shifts and race formation in Rhagoletis.
abstract: Tephritid fruit flies belonging to the Rhagoletis pomonella sibling species complex are controversial because they have been proposed to diverge in sympatry (in the absence of geographic isolation) by shifting and adapting to new host plants. Here, we report evidence suggesting a surprising source of genetic variation contributing to sympatric host shifts for these flies. From DNA sequence data for three nuclear loci and mtDNA, we infer that an ancestral, hawthorn-infesting R. pomonella population became geographically subdivided into Mexican and North American isolates approximately 1.57 million years ago. Episodes of gene flow from Mexico subsequently infused the North American population with inversion polymorphism affecting key diapause traits, forming adaptive clines. Sometime later (perhaps +/-1 million years), diapause variation in the latitudinal clines appears to have aided North American flies in adapting to a variety of plants with differing fruiting times, helping to spawn several new taxa. Thus, important raw genetic material facilitating the adaptive radiation of R. pomonella originated in a different time and place than the proximate ecological host shifts triggering sympatric divergence.
authors.affiliation: Department of Biological Sciences, P.O. Box 369, Galvin Life Science Center, University of Notre Dame, Notre Dame, IN 46556-0369, USA. feder.2@nd.edu
authors.forename: Jeffrey L
authors.initials: JL
authors.lastname: Feder
authors.forename: Stewart H
authors.initials: SH
authors.lastname: Berlocher
authors.forename: Joseph B
authors.initials: JB
authors.lastname: Roethele
authors.forename: Hattie
authors.initials: H
authors.lastname: Dambroski
authors.forename: James J
authors.initials: JJ
authors.lastname: Smith
authors.forename: William L
authors.initials: WL
authors.lastname: Perry
authors.forename: Vesna
authors.initials: V
authors.lastname: Gavrilovic
authors.forename: Kenneth E
authors.initials: KE
authors.lastname: Filchak
authors.forename: Juan
authors.initials: J
authors.lastname: Rull
authors.forename: Martin
authors.initials: M
authors.lastname: Aluja
mesh_terms: D000818:Animals; D001483:Base Sequence; D004272:DNA, Mitochondrial / Q000235:genetics; D004463:Ecology; D014644:Genetic Variation; D008969:Molecular Sequence Data; D010802:Phylogeny; D010944:Plants / Q000469:parasitology*; D033621:Tephritidae / Q000145:classification* / Q000235:genetics*
chemical_list: D004272:DNA, Mitochondrial