Phylogenetic relationships of dung beetles in the tribe Onthophagini, including the species-rich, cosmopolitan
genus Onthophagus, were inferred using whole mitochondrial genomes. Data were generated
by shotgun sequencing of mixed genomic DNA from >100 individuals on 50% of an Illumina MiSeq flow
cell. Genome assembly of the mixed reads produced contigs of 74 (nearly) complete mitogenomes. The
final dataset included representatives of Onthophagus from all biogeographic regions, closely related genera
of Onthophagini, and the related tribes Onitini and Oniticellini. The analysis defined four major clades
of Onthophagini, which was paraphyletic for Oniticellini, with Onitini as sister group to all others. Several
(sub)genera considered as members of Onthophagus in the older literature formed separate deep lineages.
All New World species of Onthophagus formed a monophyletic group, and the Australian taxa are confined
to a single or two closely related clades, one of which forms the sister group of the New World species.
Dating the tree by constraining the basal splits with existing calibrations of Scarabaeoidea suggests
an origin of Onthophagini sensu lato in the Eocene and a rapid spread from an African ancestral stock into
the Oriental region, and secondarily to Australia and the Americas at about 20–24 Mya. The successful
assembly of mitogenomes and the well-supported tree obtained from these sequences demonstrates
the power of shotgun sequencing from total genomic DNA of species pools as an efficient tool in
genus-level phylogenetics.
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