Genetic and selective responses to artificial selection on wing shape. Jose D Aponte, Ellen Kosman, Andres Plata Stapper, Zach Boudreau, Mollie Taylor, Lisa Hollensead, Karalyn Aronow, Don Levitan, David Houle. Biological Science, Florida State university, Tallahassee, FL.

   To assess if available standing genetic variation could generate novel varieties of wing shape, we selected in 2 directionsexpansion and contraction (referred to as up and down, respectively) of the 2nd and 5th longitudinal veins in a lab-maintained Drosophila melanogaster population. In just 16 generations, we were able to select out of the range of variation present in the subgenus Sophophora entirely in the up direction and partially in the down direction. Interestingly, the intersections of the 3rd and 4th vein with the margin of the wing were also altered outside of the range of the subgenus despite not having been direct targets of selection. We then asked if the constraint in shape variation found in Sophophora is due to a selective pressure related to flight or mate preference. We performed a mark-release-recapture experiment to assay flight differences among the selected populations. We also performed a mate choice assay to detect differential mating preferences among the selected populations. We discovered that, while there is no difference in flight performance between selected and control flies, females tend to mate with unselected, wild-type males. Finally, we measured the magnitude of genetic response attributable to the phenotypic response seen in the selected populations. As the placement of the 2nd and 5th longitudinal veins is controlled by Decapentaplegic signalling, we measured expression of several downstream components of the core pathway and found no significant differences among selection treatments. Taken together, we conclude that sexual selection maintains wing shape variation and that 2nd and 5th longitudinal vein placement is likely influenced by factors outside of the canonical pathway.