title: Evolution of stickleback in 50 years on earthquake-uplifted islands.
abstract: How rapidly can animal populations in the wild evolve when faced with sudden environmental shifts? Uplift during the 1964 Great Alaska Earthquake abruptly created freshwater ponds on multiple islands in Prince William Sound and the Gulf of Alaska. In the short time since the earthquake, the phenotypes of resident freshwater threespine stickleback fish on at least three of these islands have changed dramatically from their oceanic ancestors. To test the hypothesis that these freshwater populations were derived from oceanic ancestors only 50 y ago, we generated over 130,000 single-nucleotide polymorphism genotypes from more than 1,000 individuals using restriction site-associated DNA sequencing (RAD-seq). Population genomic analyses of these data support the hypothesis of recent and repeated, independent colonization of freshwater habitats by oceanic ancestors. We find evidence of recurrent gene flow between oceanic and freshwater ecotypes where they co-occur. Our data implicate natural selection in phenotypic diversification and support the hypothesis that the metapopulation organization of this species helps maintain a large pool of genetic variation that can be redeployed rapidly when oceanic stickleback colonize freshwater environments. We find that the freshwater populations, despite population genetic analyses clearly supporting their young age, have diverged phenotypically from oceanic ancestors to nearly the same extent as populations that were likely founded thousands of years ago. Our results support the intriguing hypothesis that most stickleback evolution in fresh water occurs within the first few decades after invasion of a novel environment.
authors.affiliation: School of Fisheries and Ocean Sciences, University of Alaska Fairbanks, Fairbanks, AK 99775; Department of Biological Sciences, University of Alaska Anchorage, Anchorage, AK 99508;
authors.forename: Emily A
authors.initials: EA
authors.lastname: Lescak
authors.affiliation: Institute of Ecology and Evolution, University of Oregon, Eugene, OR 97403;
authors.forename: Susan L
authors.initials: SL
authors.lastname: Bassham
authors.affiliation: Institute of Ecology and Evolution, University of Oregon, Eugene, OR 97403; Department of Animal Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801.
authors.forename: Julian
authors.initials: J
authors.lastname: Catchen
authors.affiliation: Department of Biological Sciences, University of Alaska Anchorage, Anchorage, AK 99508;
authors.forename: Ofer
authors.initials: O
authors.lastname: Gelmond
authors.affiliation: Department of Biological Sciences, University of Alaska Anchorage, Anchorage, AK 99508;
authors.forename: Mary L
authors.initials: ML
authors.lastname: Sherbick
authors.affiliation: Department of Biological Sciences, University of Alaska Anchorage, Anchorage, AK 99508;
authors.forename: Frank A
authors.initials: FA
authors.lastname: von Hippel
authors.affiliation: Institute of Ecology and Evolution, University of Oregon, Eugene, OR 97403; wcresko@uoregon.edu.
authors.forename: William A
authors.identifier: 0000-0002-3496-8074
authors.initials: WA
authors.lastname: Cresko
mesh_terms: D000413:Alaska; D000818:Animals; D005075:Biological Evolution; D055866:Earthquakes; D017753:Ecosystem; D005618:Fresh Water; D051456:Gene Flow; D014644:Genetic Variation; D005828:Genetics, Population; D005838:Genotype; D005843:Geography; D062312:Islands; D009792:Oceans and Seas; D010641:Phenotype; D010802:Phylogeny; D020641:Polymorphism, Single Nucleotide; D023701:Smegmamorpha / Q000145:classification / Q000235:genetics / Q000502:physiology*
keywords: adaptation; contemporary evolution; ecological divergence; metapopulation; population genomics