Determining biogeographical patterns of dispersal and diversification in oscine passerine birds in Australia, Southeast Asia and Africa

Aim Several independent studies suggest that oscine passerine birds originated in Eastern Gondwana/Australia and from there spread to Southeast Asia and then to Africa. A recently constructed supertree including 1724 oscine taxa forms the basis for this study, in which we present a more detailed hypothesis of this out-of-Australia scenario. Location Australia, Africa, Southeast Asia, western Pacific, Indian Ocean. Methods We used the computer program DIVA to identify putative ancestral areas for each node. We also applied a molecular clock calibrated with three recently conducted studies of passerines to estimate the ages of basal nodes. Although these time estimates are rough they give some indication that, together with the putative ancestral areas, they can be compared with known events of plate tectonic movements in the Australian, Southeast Asian and western Pacific regions. Results The DIVA analysis shows that Basal Corvida and Crown Corvida originated in Australia. Ancestral nodes for Picathartes/Chaetops and Passerida originated in Africa, and the basal nodes of Sylvioidea also originated in Africa. For Muscicapoidea and Passeroidea we were unable to establish ancestral patterns. The molecular clock showed that Crown Corvida radiated between 20 and 30 Ma whereas Basal Corvida and the Passerida clade radiated from c. 45 to 50 Ma. Main conclusions Both approaches agree that: (1) Crown Corvida spread from Australia to Southeast Asia, with several dispersal events around the time when the terranes of Australian and Indomalayan origin came close together some 15 Ma, and (2) a single dispersal event went from Australia across the Indian Ocean to Africa c. 45-50 Ma, leading to the very large radiation of the parvorder Passerida. The latter hypothesis is novel, and contrary to the general view that oscines spread exclusively via Southeast Asia.