The Eastern A race of Drosophila athabasca is a subspecies of fruit fly (soon to be officially reclassified as its own species) found in the northern United States and Canada. The Easten A subspecies differs from its two sister subspecies, Eastern B and Westnorthern, in two major aspects: male courtship song and female song preference. The three subspecies display nearly complete sexual isolation as a consequence of these differences. The sexual isolation in this system is so strong that it has driven speciation at a remarkably fast rate.
While it appears that sexual selection is the driver of speciation, we still do not know why there is sexual selection on this secondary sexual male trait in the first place (i.e. why do females have a preference for specific male courtship songs)? Two of the prevailing hypotheses for mechanisms of sexual selection are the "good genes model" and the "sexy son hypothesis." The good genes model proposes that females select males that they believe will provide them with some sort of benefit, basing their preferences on a seemingly unrelated criterion (in this case, the male courtship song). Benefits gained may be direct (such as helping the female's longevity) or indirect (such as improving the longevity of the female's offspring). Conversely, the sexy sons hypothesis states that females choose males with attractive traits because those traits will be passed on to their sons as well, effectively increasing the females' chances of passing on their genes through their sons.
In the present research we are testing which of these two models is acting on Eastern A. By examining the physical traits and courtship songs of winner fathers (flies which successfully mated) and loser fathers (flies which did not mate until placed in a scenario where the female had no other males to choose from), as well as the physical traits, courtship songs, and fecundities of their sons, we hope to identify patterns of inheritance and fecundity which will reveal which model of sexual selection is acting on the system. Discovering which model is acting on the system will serve to provide a striking example of the ways in which sexual selection can enact change on a species. This information can then be applied to other species where sexual selection has occurred or is presently occurring in order to better understand them.