The RoyalMess project aims to understand why some ant larvae can become nearly sterile individuals with short lifespan (the worker caste) while others can develop as large hyper-fertile individuals that can live up to 30 years (the queen caste). Royalty in social insects is typically environmentally acquired rather than genetically determined. However, this is not the case in an exceptional reproductive system, known as social hybridogenesis. Here, two distinct royal lineages of ants can only produce queens by their own while they need to hybridize to produce workers. Eggs with a pure royal genome are thus genetically fated to become queens while hybrid genomes are fated to become workers. Convergent evolution toward such a baroque reproductive strategy appears common in harvester ant species, but its origin is still completely mysterious. In this project, we plan to unravel the evolution of this unique system via cutting-edge genomic and molecular approaches.
1. Prevalence of social hybridogenesis: we will use genome-wide sequence data to identify novel occurrences of social hybridogenesis across hundred of ant species, in search for potential ecological determinants (e.g. climate or diet) that could favour evolution towards genetic caste determination.
2. History of royal lineages: we will use population genomics in three pairs of ant royal lineages to trace back their evolutionary origin. For this, we will develop new approaches to detect selection along royal lineage genomes in order to detect past hybridization events or fixation of caste-biasing alleles.
3. Identifying caste-determining genes: We will use comparative transcriptomics in early ant embryos to identify genes differentially expressed between castes before developmental divergence. Candidate genes will be experimentally validated via controlled matings or genome editing.
If successful, this project will enable the first genetic manipulation of ant royalty, deciphering how such an iconic example of phenotypic plasticity can become genetically hardwired. This might reveal how small genetic changes can trigger the most dramatic increase of fertility and longevity in the living world, which might open the door to future research for a better understanding of ageing. Overall, this research contributes to a broader understanding of evolutionary biology and the complex dynamics of eusociality. Ants in general and particularly harvester ants are considered as keystone species for ecosystems, as they participate to plant dispersion and organic material recycling. In the same time, many pest species are social insects, and cost a lot of resources to human societies. Understanding the reproductive systems of ants, their hybridization patterns and caste determination can thus provide valuable insights for either protecting their valuable ecosystem services or controlling their invasions.
