Extensive diversifi cation across islands in the echolocating Aerodramus swiftlets

Taxa that are known as “great speciators” are characterised by a rare combination of a potential to disperse coupled with a tendency not to, because extensive dispersal leads to gene flow counteracting differentiation, and too little dispersal leads to an inability to colonise new areas. Here we investigate the phylogenetic history of the genus Aerodramus, a group of echolocating swiftlets that has diversifi ed throughout the Indo-Pacific region, to gauge the level of differentiation and ascertain if traditional taxonomy provides an accurate assessment of species diversity, and find several phylogenetic relationships that challenge traditional taxonomy, especially within the A. vanikorensis species complex. We also suggest that the genus may be considered a “great speciator”, which has undergone a recent rapid radiation involving the colonisation of most islands in the Indian and Pacific oceans.