Convergent Evolutionary Traces of Genomic Innovations and Depletions in Socially Parasitic Ants

Abstract

Parasitism, a common strategy across life, often involves genomic reduction. Socially parasitic "slavemaking" ants provide an excellent model to study the evolution of this lifestyle. Here, we compared the genomes of four closely related, independently evolved parasite-host pairs and their outgroups to identify convergent patterns. While genome size and gene numbers remain relatively stable, parasites show increased positive and relaxed selection, more putative de novo genes which have recently emerged from previously non-coding regions, and a significant loss of chemical receptors, particularly those associated with the evolution of sociality. Hosts, however, retain many duplicated genes. Gene co-expression networks associated with nest-defence in hosts are rather conserved, while the network structure of raiding parasites is much more variable and reflects the independent evolutionary origin of social parasitism. Our findings suggest that while hosts primarily rely on existing molecular mechanisms for defence, parasite genome evolution is characterised by extensive, convergent gene loss, innovation, and network rewiring.