Mitogenomics of ‘old world Acraea’ butterflies reveals a highly divergent ‘Bematistes’

Afrotropical Acraeini butterflies provide a fascinating potential model system contrast with the Neotropical Heliconiini, yet their phylogeny remains largely unexplored by molecular methods and their generic level nomenclature is still contentious. To test the potential of mitogenomes in a simultaneous analysis of the radiation, we sequenced the full mitochondrial genomes of 19 African species. Analyses show the potential of mitogenomic phylogeny reconstruction in this group. Inferred relationships are largely congruent with a previous multilocus study. We confirm a monophyletic Telchinia including the Asiatic Pareba with a complicated paraphylum, traditional (sub-)genus Acraea, toward the base. The results suggest that several proposed subgenera and some species groups within Telchinia are not monophyletic, while two other (sub-) genera could possibly be combined. Telchinia was recovered without strong support as sister to the potentially interesting system of distasteful model butterflies Bematistes, a name that is suppressed in some treatments. Surprisingly, we find that this taxon has remarkably divergent mitogenomes and unexpected synapomorphic tRNA rearrangements. These gene order changes, combined with evidence for deviating dN/dS ratios and evidence for episodal diversifying selection, suggest that the ancestral Bematistes mitogenome has had a turbulent past. Our study adds genetic support for treating this clade as a distinct genus, while the alternative option, adopted by some authors, of Acraea being equivalent to Acraeini merely promotes redundancy. We pave the way for more detailed mitogenomic and multi-locus molecular analyses which can determine how many genera are needed (possibly at least six) to divide Acraeini into monophyletic groups that also facilitate communication about their biology.

Available online 24 December 2015