Phylogenetic relationships, biogeography and diversification of Coenonymphina butterflies (Nymphalidae: Satyrinae): intercontinental dispersal of a southern Gondwanan group?

Abstract

AbstractThe origins, evolutionary history and diversification of the Australian butterfly fauna are poorly known and uncertain. Two competing hypotheses have been proposed to explain the occurrence of butterflies on this isolated continental landmass. The common view is that all Australian butterflies entered the continent relatively recently from the northern hemisphere via Southeast Asia and/or mainland New Guinea (i.e. northern dispersal origin hypothesis). The alternative view is that part or all of the Australian butterfly fauna ultimately evolved in remnant or Southern Gondwana when Australia was connected to South America through Antarctica (i.e. Southern Gondwanan origin hypothesis). However, robust phylogenies with strong support for monophyly are lacking for the majority of Australian endemic butterfly lineages, thereby precluding determination of their systematic relationships and hence their geographic origins. Here, we use molecular data to reconstruct phylogenetic relationships of the globally distributed butterfly subtribe Coenonymphina (Satyrinae: Satyrini). This group represents a major component of the butterfly fauna of the wider Australasian region, with 19 genera and 71 species endemic to the region. Dating estimates extrapolated from secondary calibration sources indicate that the subtribe arose c. 48 Ma (95% credibility interval, 52–42 Ma), and the crown group first diverged in the Eocene (c. 44 Ma, 95% credibility interval 51–37 Ma). Rapid speciation events subsequently followed around the Eocence–Oligocene boundary, resulting in a near‐hard polytomy comprising short basal branches with nodes that are difficult to resolve. Based on strongly supported phylogenetic relationships and estimates of divergence times, we conclude that the group probably had its origin in the fragment of Southern Gondwana consisting of Australia, Antarctica and South America. However, we are unable to rule out the northern dispersal scenario, particularly as Coenonymphina are closely related to a set of predominantly Asian lineages. Dispersal and extinction events following the final break‐up of Gondwana have played a pivotal role in shaping the extant distributions of the group.