Does evolution of plumage patterns and of migratory behaviour in Apodini swifts (Aves: Apodiformes) follow distributional range shifts?

The Apodini swifts in the Old World serve as an example for a recent radiation on an intercontinental scale on the one hand. On the other hand they provide a model for the interplay of trait and distributional range evolution with speciation, extinction and trait transition rates on a low taxonomic level (23 extant taxa). Swifts are well adapted to a life mostly in the air and to long-distance movements. Their overall colouration is dull, but lighter feather patches of chin and rump stand out as visual signals. Only few Apodini taxa breed outside the tropics; they are the only species in the study group that migrate long distances to wintering grounds in the tropics and subtropics. We reconstructed a dated molecular phylogeny including all species, numerous outgroups and fossil constraints. Several methods were used for historical biogeography and two models for the study of trait evolution. We finally correlated trait expression with geographic status. The differentiation of the Apodini took place in less than 9 Ma. Their ancestral range most likely comprised large parts of the Old-World tropics, although the majority of extant taxa breed in the Afrotropic and the closest relatives occur in the Indomalayan. The expression of all three investigated traits increased speciation rates and the traits were more likely lost than gained. Chin patches are found in almost all species, so that no association with phylogeny or range could be found. Rump patches showed a phylogenetic signal and were correlated with Indomalayan distribution. Apodini swifts performed long-distance migration whenever they expanded their range to temperate latitudes during warm periods, repeatedly in the Pleistocene.