Genomic variation data for the wagtail hybrid zone

Genome-wide variation in introgression rates across hybrid zones offers a
powerful opportunity for studying population differentiation. One poorly
understood pattern of introgression is the geographic displacement of a
trait implicated in lineage divergence from genome-wide population
boundaries. While difficult to interpret, this pattern can facilitate the
dissection of trait genetic architecture because traits become uncoupled
from their ancestral genomic background. We studied an example of trait
displacement generated by the introgression of head plumage coloration
from personata to alba subspecies of
the white wagtail. A previous study of the wagtail hybrid zone in Siberia
revealed that the geographic transition in this sexual signal that
mediates assortative mating was offset from other traits and genetic
markers. We show that head plumage is associated with two small genetic
regions. Despite having a simple genetic architecture, head plumage
inheritance is consistent with partial dominance and epistasis, which
could contribute to its asymmetric introgression.