title: Mayr, Dobzhansky, and Bush and the complexities of sympatric speciation in Rhagoletis.
abstract: The Rhagoletis pomonella sibling species complex is a model for sympatric speciation by means of host plant shifting. However, genetic variation aiding the sympatric radiation of the group in the United States may have geographic roots. Inversions on chromosomes 1-3 affecting diapause traits adapting flies to differences in host fruiting phenology appear to exist in the United States because of a series of secondary introgression events from Mexico. Here, we investigate whether these inverted regions of the genome may have subsequently evolved to become more recalcitrant to introgression relative to collinear regions, consistent with new models for chromosomal speciation. As predicted by the models, gene trees for six nuclear loci mapping to chromosomes other than 1-3 tended to have shallower node depths separating Mexican and U.S. haplotypes relative to an outgroup sequence than nine genes residing on chromosomes 1-3. We discuss the implications of secondary contact and differential introgression with respect to sympatric host race formation and speciation in Rhagoletis, reconciling some of the seemingly dichotomous views of Mayr, Dobzhansky, and Bush concerning modes of divergence.
authors.affiliation: Department of Biological Sciences, University of Notre Dame, Galvin Life Science Center, IN 46556-0369, USA. feder.2@nd.edu
authors.forename: Jeffrey L
authors.initials: JL
authors.lastname: Feder
authors.forename: Xianfa
authors.initials: X
authors.lastname: Xie
authors.forename: Juan
authors.initials: J
authors.lastname: Rull
authors.forename: Sebastian
authors.initials: S
authors.lastname: Velez
authors.forename: Andrew
authors.initials: A
authors.lastname: Forbes
authors.forename: Brian
authors.initials: B
authors.lastname: Leung
authors.forename: Hattie
authors.initials: H
authors.lastname: Dambroski
authors.forename: Kenneth E
authors.initials: KE
authors.lastname: Filchak
authors.forename: Martin
authors.initials: M
authors.lastname: Aluja
mesh_terms: D000818:Animals; D005075:Biological Evolution; D002467:Cell Nucleus / Q000235:genetics; D004272:DNA, Mitochondrial / Q000235:genetics; D008954:Models, Biological; D008969:Molecular Sequence Data; D009656:North America; D010802:Phylogeny; D012641:Selection, Genetic; D013045:Species Specificity; D033621:Tephritidae / Q000145:classification* / Q000235:genetics*
chemical_list: D004272:DNA, Mitochondrial