Genomic variation in the black-throated green warbler (Setophaga virens)
suggests divergence in a disjunct Atlantic Coastal Plain population (S.
New World wood warblers (family: Parulidae) can exhibit strong
phenotypic differences among species, particularly in song and plumage.
However, within-species variation in these warblers—often designated
as subspecies—is much more subtle and has led to significant debate
over the origin, maintenance, and conservation status of populations
that differ. A species that exhibits controversial subspecific status is
the black-throated green warbler (Setophaga virens), a
Neotropical-Nearctic migrant that breeds throughout eastern and boreal
North America with several isolated populations at the margins of its
range. In particular, uncertainty has lingered over the status of S. v.
waynei, a disjunct population along the southeast Atlantic Coastal Plain
of the United States that differs morphologically and ecologically from
the nominate subspecies. Despite its unique circumstances, the
subspecific status of S. v. waynei remains questionable in the absence
of any population-wide genomic analyses. Here, we employ whole-genome
resequencing to estimate the genetic distinctiveness among samples
collected across the entirety of S. virens breeding range, including
from putative S. v. waynei. Despite detecting low global differentiation
(FST = 0.027) across the entire species, we observed discrete genetic
clustering among S. v. waynei. Principal components analysis of
genome-wide differences shows the main axis of variation separates S. v.
waynei from all other S. v. virens samples. We also found that S. v.
waynei is most similar to another isolated population from the Piedmont
of North Carolina and detected evidence of a historical north-to-south
geographic dispersal among the entire complex. Combined with previously
documented ecological and morphological distinctness, our results
support that S. v. waynei be considered a distinct and recognized
subspecies worthy of targeted conservation efforts.