Phylogeny of the Myrmecia bulldog ants reveals new insights into their biogeographic history and the evolution of social parasitism

The ants in the subfamily Myrmeciinae are conspicuous predators endemic to Australia and only the single species Myrmecia apicalis inhabits New Caledonia. Myrmecia ants present morphological, social, and behavioral traits that are not specialized in comparison to other groups of ants. We reconstructed the evolutionary history of the subfamily to test hypotheses about the biogeographic history of the species M. apicalis and the evolution of social parasitism in the subfamily, as well as to assess the internal taxonomic classification. We targeted Ultra Conserved Elements (UCEs) as molecular markers for the single species in Nothomyrmecia macrops, as well as 77 out of the 93 known Myrmecia species and aligned about ~2258 loci per taxon to infer a maximum likelihood phylogeny. We integrated the resulting phylogeny with the updated fossil record of the subfamily and the paleogeographic context of New Caledonia Island. We estimated that the Myrmeciinae ants shared a common ancestor ~72 Ma and that the current disjunt geographic distribution of M. apicalis was driven by long-distance dispersion from the Australian mainland to the island of New Caledonia ~16 Ma. We also inferred that M. inquilina is the single social parasite species in the genus Myrmecia up to date, which recently evolved in sympatry with one of the known host species M. nigriceps via the intraspecific route to evolution of social parasitism. Finally, our results indicate that the previously established taxonomic species groups are non-monophyletic, which indicates that the internal taxonomic classification of Myrmecia needs revision. Our study enhances our understanding of the assembly of the Australasian fauna, the evolution of species interactions such as social parasitism and provides foundation for future comparative research about the biology of the Myrmeciinae ants.