FIG. 3.—

Chronograms showing divergence times among parrot genera based a Bayesian relaxed-clock approach, with 2 alternative dates for the basal divergence between the New Zealand endemics Nestor and Strigops and the remaining psittaciforms: (a) node dated to 50 MYA, based on the hypothesized divergence between modern psittaciforms and fossils dated to the Lower Eocene; and (b) node dated to 82 MYA, based on the split between New Zealand and Gondwana. Uncertainty in the timing of these alternative divergences is incorporated with both calibration estimates representing means of normal distributions with SD = 2; error bars on the nodes illustrate the 95% HPD of node ages. Shaded vertical bars indicate timing of major geological events that may have contributed to diversification through vicariance: separation of New Zealand from Gondwana, 80–85 MYA; the K/T boundary, 65 MYA; the initial separation of Australia from East Antarctica, 58–61 MYA; the final separation of Australia from East Antarctica, 36–41 MYA; the final separation of South America from West Antarctica, 28–32 MYA; and Australia and New Guinea approach southeast Asia, 20–24 MYA.