Phylogeny and historical biogeography of the subtribe Aporiina (Lepidoptera: Pieridae): Implications for the origin of Australian butterflies

The Australian fauna is composed of several major biogeographical elements reflecting different spatial and temporal histories. Two groups of particular interest are the Gondwanan Element, reflecting an ancient origin in Gondwana or southern Gondwana (southern vicariance hypothesis), and the Asian Element, reflecting a more recent origin in Asia, Eurasia or Laurasia (northern dispersal hypothesis). Theories regarding the origin and evolution of butterflies (Hesperioidea, Papilionoidea) in Australia are controversial, with no clear consensus. Here, we investigate the phylogenetic and historical biogeographical relationships of the subtribe Aporiina, a widespread taxon with disjunct distributions in each of the major zoogeographical regions. Attention is paid to origins of the subtribe in the Australian Region for which several conflicting hypotheses have been proposed for the Old World genus Delias Hübner. Our phylogenetic reconstruction was based on analysis of fragments of two nuclear genes (elongation factor-1α, wingless) and one mitochondrial gene (cytochrome oxidase subunit I) for 30 taxa. Phylogenetic analyses based on maximum parsimony, maximum likelihood and Bayesian inference of the combined data set (2729 bp; 917 parsimony informative characters) recovered six major lineages within the monophyletic Aporiina, with the following topology: (Cepora + Prioneris + (Mylothris + (Aporia + Delias group + Catasticta group))). Given a probable age of origin of the stem-group near the Cretaceous/Tertiary boundary (69-54 Mya), followed by diversification of the crown-group in the early to mid Tertiary (57-45 Mya), we show that an origin of the Aporiina in either southern Gondwana or Laurasia is equally parsimonious, and that dispersal has played a major role in shaping the underlying phylogenetic pattern. We tentatively conclude that an origin in southern Gondwanan is more likely; however, neither hypothesis satisfactorily explains the present-day distribution, and additional lower-level phylogenies are needed to determine the directionality of dispersal events of several taxa and to reject one hypothesis over the other. Dispersal is inferred to have occurred primarily during cooler periods when land bridges or stepping-stones were available between many of the zoogeographical regions.