Abstracts (first author)
Testing evolutionary models for the maintenance of same-sex sexual behaviour
The evolutionary maintenance of same-sex sexual behaviour (SSB) is an enduring mystery because of its apparent negative impact on reproductive fitness. Two influential genetic models of SSB were developed several years ago by Sergey Gavrilets and William Rice: SSB might be maintained by sexually antagonistic selection for fitness-increasing traits in the opposite sex, and/or it might result from overdominance if alleles enhancing its expression are maintained by a heterozygote advantage. These models make distinct predictions about the genetic architecture of SSB and its correlations with male and female fitness. We present results of an experiment to empirically test these predictions using the Drosophila Genome Reference Panel. We screened 50 highly-inbred, genome-sequenced D. melanogaster lines for male SSB and performed a series of crosses between high and low lines designed to discriminate the two hypotheses. There was substantial additive genetic variation for SSB, strong effects of the social environment, and evidence for G x E. We will discuss genetic variance components contributing to this behaviour, candidate loci found to be strongly associated with its expression, context-dependence of the influence of those loci, and effects of SSB on fitness of males and females. Taken together, the results enable us to statistically compare support for either hypothesis – sexual antagonism vs. overdominance – and provide an intriguing contrast with Drosophila knock-out studies that have found a wide assortment of genes that might contribute to variation in male SSB.