Parallel and convergent evolution in genes underlying seasonal migration

Seasonal migration has fascinated scientists and natural historians for
centuries.  While the genetic basis of migration has been widely
studied across different taxa, there is little consensus regarding which
genomic regions play a role in the ability to migrate and whether they are
similar across species.  Here, we examine the genetic basis of
intraspecific variation within and between distinct migratory phenotypes
in a songbird. We focus on the Common Yellowthroat (Geothlypis trichas) as
a model system because the polyphyletic origin of eastern and western
clades across North America provides a strong framework for understanding
the extent to which there has been parallel or convergent evolution in the
genes associated with migratory behavior.  First, we investigate
genome-wide population genetic structure in the Common Yellowthroat in 196
individuals collected from 22 locations across breeding range. Then, to
identify candidate genes involved in seasonal migration, we identify
signals of putative selection in replicate comparisons between resident
and migratory phenotypes within and between eastern and western clades.
Overall, we find wide-spread support for parallel evolution at the genic
level, particularly in genes that mediate biological
timekeeping.  However, we find little evidence of parallelism at
the individual SNP level, supporting the idea that there are multiple
genetic pathways involved in the modulation of migration.