Testing genetic models of same-sex sexual behaviour

Little is known of the evolutionary forces that maintain same-sex sexual behavior (SSB) in natural populations, despite its common occurrence. We will use 192 inbred lines of Drosophila melanogaster that have been derived from a natural population in North Carolina, to test the two main genetic models of SSB: overdominance and sexual antagonism. We will screen all inbred lines for male-male SSB to identify those containing high levels of SSB and those containing low levels of SSB. The top and bottom 5 lines will subsequently be used in crossing experiments to identify genetic components contributing to SSB. The chromosomal location, dominance relationships and correlations with fitness make clear predictions favouring the different genetic models of SSB, and by quantifying these, we will assess the likelihood that SSB is maintained under either model. The results will provide much-needed data on the genetic architecture of SSB, which is a prominent, yet often overlooked, source of variation in mating behaviour in natural populations.