The evolution and phylogeography of Danaus butterflies (Nymphalidae: Danainae)

The pantropical butterfly genus Danaus contains about ten species of aposematically colored unpalatable butterflies, including the Monarch Butterfly, Danaus plexippus. The Monarch has become a model for the study of invertebrate migration, the widespread species D. chrysippus has been studied extensively as a model of incipient speciation and of male-killing Spiroplasma infection, and many Danuas species serve as models for palatable mimetic species. However, there is no satisfactory phylogenetic estimate for relationships among Danaus species. Previous molecular phylogenetic studies of Danaus were based on limited taxon samples and a relatively small number of genes. We present a well-sampled phylogenetic analysis based on five genes from multiple specimens per species. Our analysis confirms that D. erippus is the sister species of the Monarch, and finds that this clade is sister to the Caribbean endemic D. cleophile, which has never before been included in molecular phylogenetic analyses. Danaus petilia is well differentiated from D. chrysippus from which it was recently raised from synonymy, but D. genutia and D. melanippus are not monophyletic. We discuss the taxonomic implications of our results and the potential for future comparative analyses.