Out of South-East Asia: phylogeny and biogeography of the spiny ant genus Polyrhachis Smith (Hymenoptera: Formicidae)

Spiny ants (Polyrhachis Smith) are a hyper-diverse genus of ants distributed throughout the Palaeotropics and the temperate zones of Australia. To investigate the evolution and biogeographic history of the group, we reconstructed their phylogeny and biogeography using molecular data from 209 taxa and seven genes. Our molecular data support the monophyly of Polyrhachis at the generic level and several of the 13 recognized subgenera, but not all are recovered as monophyletic. We found that Campomyrma Wheeler consists of two distinct clades that follow biogeographic affinities, that the boundaries of Hagiomyrma Wheeler are unclear depending on the analysis, that Myrma Billberg might be treated as one or two clades, and that Myrmhopla Forel is not monophyletic, as previously proposed. Our biogeographic ancestral range analyses suggest that the evolution of Polyrhachis originated in South-East Asia, with an age of the modern crown-group Polyrhachis of 58 Ma. Spiny ants dispersed out of South-East Asia to Australia several times, but only once to mainland Africa around 26 Ma.