A phylogeny of frugivorous hornbills linked to the evolution of Indian plants within Asian rainforests.

Understanding the origin and radiation of modern Asian hornbills and the influential ecological roles they play as seed dispersal agents within Asian rainforests should help reveal the evolution of these roles. We constructed a dated phylogeny of hornbills using mitochondrial DNA sequences of the cytochrome b gene and discovered that all clades leading to frugivorous hornbills originated in the mid-Eocene ∼48 Ma. This 'explosive' radiation coincided with a remarkable floral invasion of Asian rainforests from the Indian microcontinent. Analysis of phylogenetic data, in conjunction with palaeontological events, suggests that the invasion of distinctive flora comprised two waves, one during the mid-Eocene, when India was offshore of the Sunda Shelf, and the other late Eocene, when India collided with the Asian mainland. We propose that frugivorous vertebrates, such as hornbills, were present during the first wave and assisted rapid colonization of the Asian flora.