Abstract

Colonisation of novel host plants can promote diversification in butterflies because they enter new adaptive zones. African sister genera Harma and Cymothoe (Nymphalidae) contrast in species diversification: Harma is monospecific and Cymothoe comprises 74 species. They also contrast in diversity of host use: Harma larvae feed on Achariaceae only while some Cymothoe species feed on the same Achariaceae species while others are highly specialised on species of Rinorea (Violaceae). Our aim was to assess association of host plant use and increased species diversification Cymothoe. I present the first molecular phylogenetic tree of Harma and Cymothoe, based on 53 species (65%) and multiple independent genetic markers within an absolute-time framework. Patterns of diversification and host plant use based on full species sampling were analysed using Bayesian and Likelihood methods. Results confirm that Harma and Cymothoe are sisters on a branch spanning approximately 30my. Net diversification is low during the first 20my (Oligocene and Miocene) followed by a sharp increase coinciding with the origination of Cymothoe in the late Miocene. A slight but insignificant increase in the rate of diversification after colonisation of Rinorea host plants does not explain this pattern. Gradual decrease in global temperatures after the Miocene promoting habitat fragmentation and reproductive isolation in Cymothoe and their hosts can provide an alternative explanation.