Uncovering the genomic underpinnings of the convergent evolution of a major social trait
Understanding how complex traits evolve repeatedly across species remains a major challenge in biology. The number of queens in an ant colony is an important trait associated with queen lifespan and fecundity, dispersal strategies, and responses to environmental stimuli. Although colonies of most ant species have either one or multiple queens, more than twelve ant species have evolved social dimorphism: co-existence of single- and multiple-queen colonies in a population. This phenomenon presents a remarkable opportunity to discover mechanisms of convergent genetic evolution. Our proposal takes advantage of the recurrent evolution of social dimorphism in ants to understand the genomic basis of this complex trait.
Recent genomic studies have revealed that a “supergene” genomic region including hundreds of linked genes determines colony type in two distantly related ant species. However, it remains unclear to what extent supergenes underlie social dimorphism and which genes are important for the evolution of this trait. Here, we aim to elucidate general principles governing the evolution of social dimorphism at the molecular level. We will select six ant lineages in which the co-existence of the two social forms has independently evolved to accomplish three goals: 1) test whether supergenes are required for dimorphic social organization by performing genome-wide comparisons between single- and multiple-queen colonies; 2) test for similar changes in gene content or sequence across the independent origins of social dimorphism by comparing phylogenetic profiles; 3) determine whether differences in gene expression in workers of single- versus multiple-queen colonies are consistent across species by performing transcriptome-wide comparisons. Our project will provide major insights into the genetic architectures and pathways underpinning the evolution of social dimorphism, and will substantially improve our understanding of the evolution of complex phenotypes.