A global molecular phylogeny yields insights into the dispersal and invasion history of Junonia, a butterfly genus with remarkable dispersal abilities

The nymphalid butterfly genus Junonia has remarkable dispersal abilities. Occurring on every continent except Europe and Antarctica, Junonia are often among the only butterflies on remote oceanic islands. The biogeography of Junonia has been controversial, plagued by taxonomic disputes, small phylogenetic datasets, incomplete taxon sampling, and shared interspecific mitochondrial haplotypes. Junonia originated in Africa but its route into the New World remains unknown. Presented here is, to our knowledge, the most comprehensive Junonia phylogeny to date, using full mitogenomes and nuclear ribosomal RNA repeats from 40 of 47 described species. Junonia is monophyletic and the genus Salamis is its probable sister clade. Genetic exchange between Indo-Pacific Junonia villida and New World Junonia vestina is evident, suggesting a trans-Pacific route into the New World. However, in both phylogenies, the sister clades to most New World Junonia contain both African and Asian species. Multiple trans-Atlantic or trans-Pacificinvasions could have contributed to New World diversification. Hybridization and lateral transfer of mitogenomes, already well-documented in New World Junonia, also occurs in at least two Old World lineages (Junonia orithya/Junonia hierta and Junonia iphita/Junonia hedonia). Variation associated with reticulate evolution creates challenges for phylogenetic reconstruction, but also may have contributed to patterns of speciation and diversification in this genus.

Automated summary

The genus Junonia is a type of nymphalid butterfly with remarkable dispersal abilities. It is found on every continent except Europe and Antarctica, and is often the only butterfly species on remote oceanic islands. The biogeography and phylogeny of Junonia have been a subject of controversy and research limitations. However, this study presents the most comprehensive Junonia phylogeny to date, using complete mitogenomes and nuclear ribosomal RNA repeats from 40 out of 47 known species. The results show that Junonia is monophyletic, with the genus Salamis as its probable sister clade. There is evidence of genetic exchange between Junonia species from the Indo-Pacific region and the New World, suggesting a trans-Pacific route into the New World. Multiple trans-Atlantic or trans-Pacific invasions may have contributed to diversification in the New World. Hybridization and lateral transfer of mitogenomes were also observed, both in the New World and in certain Old World lineages. Variation associated with reticulate evolution poses challenges for phylogenetic reconstruction but may have played a role in speciation and diversification patterns.