title: The intensity of selection acting on the couch potato gene--spatial-temporal variation in a diapause cline.
abstract: Cosmopolitan populations of Drosophila melanogaster have co-opted a form of reproductive diapause to overwinter in northern populations. Polymorphism in the couch potato gene has been implicated in genetic variation for this diapause trait. Using a collection of 20 populations from Florida to Canada and 11 collections from 3 years in a Pennsylvania orchard, we estimated the allele frequencies for 15 single nucleotide polymorphisms (SNPs) in the couch potato gene. These include the specific polymorphism associated with diapause inducability. We find that the SNP polymorphism, 48034(A/T), is correlated with latitude and its frequencies are predicted by the incidence of diapause trait. We find that the clinal patterns for cpo SNPs sampled in 1997 are similar to the same SNPs sampled in 2009-2010. SNPs that show apparent associations with cpo expression are also clinal with the low-expression allele increasing in frequency, as would be predicted from functional knockout studies of cpo. Finally, we see a significant pattern where the frequency of the diapause-causing allele drops in frequency during the summer season, consistent with the drop in the incidence of the diapause trait. The selection required to drive this response is large, roughly 24% to 59% per generation depending on the degree of dominance.
authors.affiliation: Department of Ecology and Evolution, Stony Brook University, Stony Brook, New York.
authors.forename: Rodrigo
authors.initials: R
authors.lastname: Cogni
authors.forename: Caitlin
authors.initials: C
authors.lastname: Kuczynski
authors.forename: Spencer
authors.initials: S
authors.lastname: Koury
authors.forename: Erik
authors.initials: E
authors.lastname: Lavington
authors.forename: Emily L
authors.initials: EL
authors.lastname: Behrman
authors.forename: Katherine R
authors.initials: KR
authors.lastname: O'Brien
authors.forename: Paul S
authors.initials: PS
authors.lastname: Schmidt
authors.forename: Walter F
authors.initials: WF
authors.lastname: Eanes
mesh_terms: D000818:Animals; D064666:Diapause, Insect / Q000235:genetics*; D029721:Drosophila Proteins / Q000235:genetics*; D004331:Drosophila melanogaster / Q000235:genetics* / Q000502:physiology; D019143:Evolution, Molecular; D005787:Gene Frequency; D009687:Nuclear Proteins / Q000235:genetics*; D020641:Polymorphism, Single Nucleotide; D012641:Selection, Genetic
chemical_list: D029721:Drosophila Proteins; D009687:Nuclear Proteins; C078019:cpo protein, Drosophila
keywords: Adaptation; gene flow; life-history evolution; physiology; population genetics; population structure