The New World diversification and origins of the Buckeye butterflies (genus Junonia, Nymphalidae: Nymphalini)

Abstract

The New World buckeye butterflies (genus Junonia) are valuable experimental model organisms, but the taxonomy of this group has been problematic and contentious. I have clarified the taxonomy of the Junonia species in the Western Hemisphere using molecular and morphological data from contemporary and museum collections, with a focus on the South American Junonia species. To do this, I have developed and validated a restriction-digest based mode of mitochondrial genotyping for use with both contemporary and historical specimens, which may be used once species have been identified based on morphology. An improved taxonomy will encourage and support further comparative biology research in Junonia. I have also tested the hypothesis that Junonia populations in the New World comprise a ring species. I falsified one of the predictions of the ring species hypothesis by detecting no discontinuity in gene flow based on mitochondrial genotype data in the proposed area of overlap between the ends of the ring. This region of overlap is where a true ring species would exhibit reproductive isolation. To clarify the relationships among Junonia species and address the issue of the origins of the New World Junonia, an extensive molecular phylogenetic analysis was completed using both full mitogenome and nuclear rRNA repeat sequences. Like previous molecular phylogenies based on much smaller DNA fragment data sets, the species level relationships of the New World Junonia were inconclusive because they were obscured by recent divergence of lineages and gene flow between species. Based on full mitogenome and rRNA repeat phylogenies, I was able to add additional support for a trans-Pacific route of Asian species responsible for the New World Junonia diversification, though some data suggest that genetic contributions from trans-Atlantic migrants from other Junonia lineages is also possible. The New World Junonia may be an example of lineage hybridization contributing to rapid diversification and adaptive radiation.