Data from: Outlier analyses to test for local adaptation to breeding grounds in a migratory arctic seabird

Investigating the extent (or the existence) of local adaptation is crucial
to understanding how populations adapt. When experiments or fitness
measurements are difficult or impossible to perform in natural
populations, genomic techniques allow us to investigate local adaptation
through the comparison of allele frequencies and outlier loci along
environmental clines. The thick-billed murre (Uria lomvia) is a highly
philopatric colonial arctic seabird that occupies a significant
environmental gradient, shows marked phenotypic differences among
colonies, and has large effective population sizes. To test whether
thick-billed murres from five colonies along the eastern Canadian Arctic
coast show genomic signatures of local adaptation to their breeding
grounds, we analyzed geographic variation in genome-wide markers mapped to
a newly assembled thick-billed murre reference genome. We used outlier
analyses to detect loci putatively under selection, and clustering
analyses to investigate patterns of differentiation based on 2220
genomewide single nucleotide polymorphisms (SNPs) and 137 outlier SNPs. We
found no evidence of population structure among colonies using all loci
but found population structure based on outliers only, where birds from
the two northernmost colonies (Minarets and Prince Leopold) grouped with
birds from the southernmost colony (Gannet), and birds from Coats and
Akpatok were distinct from all other colonies. Although results from our
analyses did not support local adaptation along the latitudinal cline of
breeding colonies, outlier loci grouped birds from different colonies
according to their non-breeding distributions, suggesting that outliers
may be informative about adaptation and/or demographic connectivity
associated with their migration patterns or nonbreeding grounds.