With nearly 300 species, the infraorder Meliphagides represents one of the largest and most conspicuous Australasian bird radiations. Although the group has been the focus of a number of recent phylogenetic studies, a comprehensive species-level phylogenetic hypothesis is still lacking. This has impeded the assessment of broad-scale evolutionary, biogeographic and ecological hypotheses. In the present study, we use a supermatrix approach including five mitochondrial and four nuclear markers to infer a time-calibrated phylogeny of the Meliphagides. Our phylogeny, which includes 286 of the 289 (99%) currently recognized species, is largely congruent with previous estimates. However, the addition of 60 newly sequenced species reveals some novel relationships. Our biogeographic analyses suggest an Australian origin for the group in the early Oligocene (31.3Mya, 95% HPD 25.2-38.2Mya). In addition, we find that dispersal events out of Australia have been numerous and frequent, particularly to New Guinea, which has also been the source of multiple back-colonizations to the Australian mainland. The phylogeny provides an important framework for studying a wide variety of macroecological and macroevolutionary themes, including character evolution, origin and timing of diversification, biogeographic patterns and species responses to climate change.

BackgroundThe avian Order Passeriformes is an enormously species-rich group, which comprises almost 60% of all living bird species. This diverse order is believed to have originated before the break-up of Gondwana in the late Cretaceous. However, previous molecular dating studies have relied heavily on the geological split between New Zealand and Antarctica, assumed to have occurred 85–82 Mya, for calibrating the molecular clock and might thus be circular in their argument.ResultsThis study provides a time-scale for the evolution of the major clades of passerines using seven nuclear markers, five taxonomically well-determined passerine fossils, and an updated interpretation of the New Zealand split from Antarctica 85–52 Mya in a Bayesian relaxed-clock approach. We also assess how different interpretations of the New Zealand–Antarctica vicariance event influence our age estimates. Our results suggest that the diversification of Passeriformes began in the late Cretaceous or early Cenozoic. Removing the root calibration for the New Zealand–Antarctica vicariance event (85–52 Mya) dramatically increases the 95% credibility intervals and leads to unrealistically old age estimates. We assess the individual characteristics of the seven nuclear genes analyzed in our study. Our analyses provide estimates of divergence times for the major groups of passerines, which can be used as secondary calibration points in future molecular studies.ConclusionsOur analysis takes recent paleontological and geological findings into account and provides the best estimate of the passerine evolutionary time-scale currently available. This time-scale provides a temporal framework for further biogeographical, ecological, and co-evolutionary studies of the largest bird radiation, and adds to the growing support for a Cretaceous origin of Passeriformes.

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