Data from: Multiple sexual signals and behavioral reproductive isolation in a diverging population

Sexual trait divergence has been shown to play a role in the evolution of
reproductive isolation. While variation in multiple sexual signals is
common among closely related species, little is known about the role of
these different axes of phenotype variation with respect to the evolution
of behavioral reproductive isolation. Here we study a unique population of
barn swallows (Hirundo rustica transitiva) which can only be distinguished
phenotypically from its neighboring populations based on two features of
male plumage: exaggerated expression of both long tail streamers and dark
ventral coloration. Using phenotype manipulation experiments, we conducted
a paternity study to examine whether both traits are sexually selected.
Our results show that an exaggerated form of the local male phenotype
(with both tail elongation and color darkening) is favored by local
females whereas males whose phenotypes were manipulated to look like males
of neighboring subspecies suffered paternity losses from their social
mates. These results confirm the multiple signaling role of the unique
tail and color combination in our diverging population and suggest a novel
possibility according to which multiple sexual signals may also be used to
discriminate among males from nearby populations when pre-zygotic
reproductive isolation is adaptive.