Data from: Evolution of stickleback in 50 years on earthquake-uplifted islands

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.