The genetic basis for fruit odor discrimination in Rhagoletis flies and its significance for sympatric host shifts

Hattie R. Dambroski, Charles Linn, Stewart H. Berlocher, Andrew A. Forbes, Wendell Roelofs, Jeffrey L. Feder

Research output: Contribution to journalArticle

Abstract

Rhagoletis pomonella (Diptera: Tephritidae) use volatile compounds emitted from the surface of ripening fruit as important chemosensory cues for recognizing and distinguishing among alternative host plants. Host choice is of evolutionary significance in Rhagoletis because these flies mate on or near the fruit of their respective host plants. Differences in host choice based on fruit odor discrimination therefore result in differential mate choice and prezygotic reproductive isolation, facilitating sympatric speciation in the absence of geographic isolation. We test for a genetic-basis for host fruit odor discrimination through an analysis of F2 and backcross hybrids constructed between apple-, hawthorn-, and flowering dogwood-infesting Rhagoletis flies. We recovered a significant proportion (30-65%) of parental apple, hawthorn, and dogwood fly response phenotypes in F2 hybrids, despite the general failure of F1 hybrids to reach odor source spheres. Segregation patterns in F3 and backcross hybrids suggest that only a modest number of allelic differences at a few loci may underlie host fruit odor discrimination. In addition, a strong bias was observed for F 2 and backcross flies to orient to the natal fruit blend of their maternal grandmother, implying the existence of cytonuclear gene interactions. We explore the implications of our findings for the evolutionary dynamics of sympatric host race formation and speciation.

Original languageEnglish (US)
Pages (from-to)1953-1964
Number of pages12
JournalEvolution
Volume59
Issue number9
DOIs
StatePublished - Sep 2005

Keywords

  • Apple maggot fly
  • Chemoreception
  • Cytonuclear interaction
  • Dogwood fly
  • Ecological speciation
  • Habitat-specific mating
  • Hawthorn fly
  • Host races
  • Hybrid incompatibility

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Genetics
  • Agricultural and Biological Sciences(all)

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