Synchronous intercontinental splits between assemblages of woodpeckers suggested by molecular data

The woodpeckers (Piciformes: Picinae) comprise a widely distributed and species-rich clade of birds that is strongly associated with trees for feeding, nesting, or both. Because of this association, woodpeckers provide a useful model for evaluating the impact of climatic and tectonic events on the diversification of forest birds during the Tertiary. In order to resolve the biogeographical history of the woodpeckers, we have analysed sequences from two nuclear introns and one mitochondrial gene using likelihood and Bayesian approaches. Our analyses favour a tropical Eurasian origin; divergences between African, Indo-Malayan and New World clades with subsequent colonizations of Africa and the New World occurred synchronously during the Middle Miocene, a period corresponding to the expansion of the C4 grasses and the uplift of the Himalayan-Tibetan plateau. The taxonomic diversification of woodpeckers at this time may be attributed to the fragmentation of forests in response to the drier climate, which in turn prevented gene flow between tropical stocks in Africa, Indo-Malaya and the New World. Our estimates of colonization times of South America predate the closure of the Panama Isthmus and support the hypothesis of a short-lived, terrestrial corridor at the end of the Miocene, 5.7 Myr BP.