Evidence from Australian mesic zone dung beetles supports their Gondwanan origin and Mesozoic diversification of the Scarabaeinae

The evolution of dung beetles remains contentious with two hypotheses reflecting Cretaceous and Paleogene origins driven by different methods. We explore biogeographic evidence and phylogeographic origins against vicariance and dispersal scenarios that attribute to the four elements of the Australian fauna using a multi-gene approach. Maximum-likelihood and Bayesian analyses supported the Australasian clade, composed of almost all Australian, New Caledonian and New Zealand endemic genera (to the exclusion of Boletoscapter). Two Australian lineages with east-west splits and few lineages with restricted, non-overlapping distrbution were identified, and biogeography models provided evidence that vicariance and founder event speciation are important processes in the diversification of Australasian scarabaeines. Our phylogenetic results are largely congruent with a mid-Cretaceous origin of the Australasian clade, the tectonic history of Gondwanaland and climatic history of the Australian continent, and provide compelling evidence that Australian dung beetles are a relictual fauna whose history is linked to mesic zone fragmentation.