Macroevolution and shifts in the feeding biology of the New World scarab beetle tribe Phanaeini (Coleoptera: Scarabaeidae: Scarabaeinae)

The New World scarab beetle tribe Phanaeini contains coprophagous, necrophagous, mycetophagous and suspected myrmecophilous species. We analyse the largest tribal molecular dataset assembled, incorporating, for the first time, the enigmatic monobasic genus Megatharsis, the thalassinus group of the subgenus Coprophanaeus (Metallophanaeus), and the subgenus Dendropaemon (Eurypodea) (formerly Tetramereia), unveiling their macroevolutionary and biogeographical history in light of Cenozoic abiotic changes and inferring shifts in feeding biology through time. We recover the contentious genus Gromphas outside an otherwise monophyletic Phanaeini. We infer Megatharsis in a clade containing the apparent myrmecophilous genus Dendropaemon, within the Coprophanaeus clade, and demonstrate that the subgenus Coprophanaeus (Metallophanaeus) is polyphyletic, whilst species groups within the subgenus Coprophanaeus (Coprophanaeus) are monophyletic. Our divergence time analyses and ancestral range estimation indicate an eastern South American origin for Phanaeini in the early Eocene, with subsequent colonization of Central America and the Nearctic during the Oligocene, long before a Panamanian land bridge. A shift to necrophagy in Coprophanaeus is possibly linked to increasing Neotropical small vertebrate diversity since the Eocene and, astonishingly, myrmecophily evolved from necrophagy 35 Mya. These drastic shifts in lifestyle are not concordant with variations in diversification rates and appear unlinked to Quaternary extinction of large mammals.