Speciation in ants: Unlocking ant diversity to study speciation (Hymenoptera: Formicidae)

Patrick Heidbreder , Patrick Krapf, Marit Kuijt, Beatriz Portinha, Michel Chapuisat, Jonna Kulmuni

Ants are among the most abundant terrestrial animals and play key roles in ecosystems across the globe. Their taxonomic and ecological diversity makes them a prime taxon for contributing to our understanding of the patterns and processes of speciation. However, studies on ants, such as those on ant diversification or taxonomy, often do not explicitly consider how their results inform or update the broader framework of speciation and reproductive isolation. Yet the wealth of taxonomic, biogeographical, behavioral, and genomic studies on ants could significantly contribute to our understanding of both micro and macroevolutionary patterns of speciation. Here, we combine microevolutionary studies on reproductive isolation and hybridization with macroevolutionary work on ant diversification to review what is known about ant speciation. We also discuss how two key features, sociality and haplodiploidy, could impact speciation and hybridization in ants. We find that, although key innovations as drivers of ant diversification have been studied, gaps exist in our understanding of reproductive isolating mechanisms in ants. However, general population features or traits, such as co-evolution within mutualistic or parasitic relationships, suggest that reproductive isolating mechanisms studied in ants may be generalizable across the tree of life. We suggest that ants could serve as valuable systems to study open questions in speciation, especially hybridization and divergence with gene flow, the genomic basis of intrinsic postzygotic isolation, and species interactions as drivers of reproductive isolation between species.