Data from: A role for migration-linked genes and genomic islands in divergence of a songbird
Ruegg, Kristen et al. (2014), Data from: A role for migration-linked genes and genomic islands in divergence of a songbird, Dryad, Dataset, https://doi.org/10.5061/dryad.73gj4
Next-generation sequencing has made it possible to begin asking questions about the process of divergence at the level of the genome. For example, recently there has been a debate around the role of “genomic islands of divergence” (i.e. blocks of outlier loci) in facilitating the process of speciation-with-gene-flow. The Swainson’s thrush, Catharus ustulatus, is a migratory songbird with two genetically-distinct subspecies that differ in a number of traits known to be involved in reproductive isolation in birds (plumage coloration, song, and migratory behavior), despite contemporary gene flow along a secondary contact zone. Here we use RAD-PE sequencing to test emerging hypotheses about the process of divergence at the level of the genome and identify genes and gene regions involved in differentiation in this migratory songbird. Our analyses revealed distinct genomic islands on 15 of the 23 chromosomes and levels of differentiation that were 2-3 orders of magnitude higher on the sex chromosomes than the autosomes. Further, an analysis of loci linked to pigmentation, song, and migratory behavior showed that genes linked to migration are significantly more differentiated then expected by chance, but that these genes lie primarily outside of the genomic islands. Overall, our analysis supports the idea that genes linked to migration play an important role in divergence in migratory songbirds, but we find no compelling evidence that the observed genomic islands are facilitating adaptive divergence in migratory behavior.