title: Do North Atlantic eels show parallel patterns of spatially varying selection?
abstract: BACKGROUND
  The two North Atlantic eel species, the European and the American eel, represent an ideal system in which to study parallel selection patterns due to their sister species status and the presence of ongoing gene flow. A panel of 80 coding-gene SNPs previously analyzed in American eel was used to genotype European eel individuals (glass eels) from 8 sampling locations across the species distribution. We tested for single-generation signatures of spatially varying selection in European eel by searching for elevated genetic differentiation using FST-based outlier tests and by testing for significant associations between allele frequencies and environmental variables.
  
  
  RESULTS
  We found signatures of possible selection at a total of 11 coding-gene SNPs. Candidate genes for local selection constituted mainly genes with a major role in metabolism as well as defense genes. Contrary to what has been found for American eel, only 2 SNPs in our study correlated with differences in temperature, which suggests that other explanatory variables may play a role. None of the genes found to be associated with explanatory variables in European eel showed any correlations with environmental factors in the previous study in American eel.
  
  
  CONCLUSIONS
  The different signatures of selection between species could be due to distinct selective pressures associated with the much longer larval migration for European eel relative to American eel. The lack of parallel selection in North Atlantic eels could also be due to most phenotypic traits being polygenic, thus reducing the likelihood of selection acting on the same genes in both species.
authors.forename: Malene G
authors.initials: MG
authors.lastname: Ulrik
authors.forename: José Martín
authors.initials: JM
authors.lastname: Pujolar
authors.forename: Anne-Laure
authors.initials: AL
authors.lastname: Ferchaud
authors.forename: Magnus W
authors.initials: MW
authors.lastname: Jacobsen
authors.forename: Thomas D
authors.initials: TD
authors.lastname: Als
authors.forename: Pierre Alexandre
authors.initials: PA
authors.lastname: Gagnaire
authors.forename: Jane
authors.initials: J
authors.lastname: Frydenberg
authors.forename: Peder K
authors.initials: PK
authors.lastname: Bøcher
authors.forename: Bjarni
authors.initials: B
authors.lastname: Jónsson
authors.forename: Louis
authors.initials: L
authors.lastname: Bernatchez
authors.affiliation: Department of Bioscience, Aarhus University, Ny Munkegade 114, Bldg, 1540, DK-8000 Aarhus C, Denmark. michael.m.hansen@biology.au.dk.
authors.forename: Michael M
authors.initials: MM
authors.lastname: Hansen
mesh_terms: D025041:Animal Migration; D000818:Animals; D004524:Eels / Q000145:classification* / Q000235:genetics* / Q000254:growth & development / Q000502:physiology; D051456:Gene Flow; D005787:Gene Frequency; D059647:Gene-Environment Interaction; D020641:Polymorphism, Single Nucleotide