The genetic basis of variation in sexual aggression: Evolution versus social plasticity

Male sexual aggression towards females is a form of sexual conflict that can result in increased fitness for males through forced copulations (FCs) or coercive matings at the cost of female lifetime fitness. We used male fruit flies (Drosophila melanogaster) as a model system to uncover the genomic contributions to variation in FC, both due to standing variation in a wild population, and due to plastic changes associated with variation in social experience. We used RNAseq to analyse whole-transcriptome differential expression (DE) in male head tissue associated with evolved changes in FC from lineages previously selected for high and low FC rate and in male flies with varying FC rates due to social experience. We identified hundreds of genes associated with evolved and plastic variation in FC, however only a small proportion (27 genes) showed consistent DE due to both modes of variation. We confirmed this trend of low concordance in gene expression effects across broader sets of genes significant in either the evolved or plastic analyses using multivariate approaches. The gene ontology terms neuropeptide hormone activity and serotonin receptor activity were significantly enriched in the set of significant genes. Of seven genes chosen for RNAi knockdown validation tests, knockdown of four genes showed the expected effect on FC behaviours. Taken together, our results provide important information about the apparently independent genetic architectures that underlie natural variation in sexual aggression due to evolution and plasticity.

Automated summary

Male sexual aggression towards females is a complex behavior influenced by both genetic and environmental factors. In this study, researchers used fruit flies as a model system to investigate the genetic contributions to variation in forced copulations (FCs). They found that hundreds of genes were associated with evolved and plastic variation in FC, but only a small proportion showed consistent differential expression in both modes of variation. Functional analysis revealed the enrichment of genes related to neuropeptide hormone activity and serotonin receptor activity. Knockdown experiments confirmed the role of four genes in FC behavior. Overall, this study provides valuable insights into the genetic architecture underlying natural variation in sexual aggression.