Data from: Co-evolving wing spots and mating displays are genetically separable traits in Drosophila

The evolution of sexual traits often involves correlated changes in
morphology and behavior. For example, in Drosophila, divergent mating
displays are often accompanied by divergent pigment patterns. To better
understand how such traits co-evolve, we investigated the genetic basis of
correlated divergence in wing pigmentation and mating display between the
sibling species Drosophila elegans and D. gunungcola. Drosophila elegans
males have an area of black pigment on their wings known as a wing spot
and appear to display this spot to females by extending their wings
laterally during courtship. By contrast, D. gunungcola lost both of these
traits. Using Multiplexed Shotgun Genotyping (MSG), we identified a ~440
kb region on the X chromosome that behaves like a genetic switch
controlling the presence or absence of male-specific wing spots. This
region includes the candidate gene optomotor-blind (omb), which plays a
critical role in patterning the Drosophila wing. The genetic basis of
divergent wing display is more complex, with at least two loci on the X
chromosome and two loci on autosomes contributing to its evolution.
Introgressing the X-linked region affecting wing spot development from D.
gunungcola into D. elegans reduced pigmentation in the wing spots but did
not affect the wing display, indicating that these are genetically
separable traits. Consistent with this observation, broader sampling of
wild D. gunungcola populations confirmed the wing spot and wing display
are evolving independently: some D. gunungcola males performed wing
displays similar to D. elegans despite lacking wing spots. These data
suggest that correlated selection pressures rather than physical linkage
or pleiotropy are responsible for the coevolution of these morphological
and behavioral traits. They also suggest that the change in morphology
evolved prior to the change in behavior.