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, 25 (10), 2141-56

A Multilocus Molecular Phylogeny of the Parrots (Psittaciformes): Support for a Gondwanan Origin During the Cretaceous

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A Multilocus Molecular Phylogeny of the Parrots (Psittaciformes): Support for a Gondwanan Origin During the Cretaceous

Timothy F Wright et al. Mol Biol Evol.

Abstract

The question of when modern birds (Neornithes) first diversified has generated much debate among avian systematists. Fossil evidence generally supports a Tertiary diversification, whereas estimates based on molecular dating favor an earlier diversification in the Cretaceous period. In this study, we used an alternate approach, the inference of historical biogeographic patterns, to test the hypothesis that the initial radiation of the Order Psittaciformes (the parrots and cockatoos) originated on the Gondwana supercontinent during the Cretaceous. We utilized broad taxonomic sampling (representatives of 69 of the 82 extant genera and 8 outgroup taxa) and multilocus molecular character sampling (3,941 bp from mitochondrial DNA (mtDNA) genes cytochrome oxidase I and NADH dehydrogenase 2 and nuclear introns of rhodopsin intron 1, tropomyosin alpha-subunit intron 5, and transforming growth factor ss-2) to generate phylogenetic hypotheses for the Psittaciformes. Analyses of the combined character partitions using maximum parsimony, maximum likelihood, and Bayesian criteria produced well-resolved and topologically similar trees in which the New Zealand taxa Strigops and Nestor (Psittacidae) were sister to all other psittaciforms and the cockatoo clade (Cacatuidae) was sister to a clade containing all remaining parrots (Psittacidae). Within this large clade of Psittacidae, some traditionally recognized tribes and subfamilies were monophyletic (e.g., Arini, Psittacini, and Loriinae), whereas several others were polyphyletic (e.g., Cyclopsittacini, Platycercini, Psittaculini, and Psittacinae). Ancestral area reconstructions using our Bayesian phylogenetic hypothesis and current distributions of genera supported the hypothesis of an Australasian origin for the Psittaciformes. Separate analyses of the timing of parrot diversification constructed with both Bayesian relaxed-clock and penalized likelihood approaches showed better agreement between geologic and diversification events in the chronograms based on a Cretaceous dating of the basal split within parrots than the chronograms based on a Tertiary dating of this split, although these data are more equivocal. Taken together, our results support a Cretaceous origin of Psittaciformes in Gondwana after the separation of Africa and the India/Madagascar block with subsequent diversification through both vicariance and dispersal. These well-resolved molecular phylogenies will be of value for comparative studies of behavior, ecology, and life history in parrots.

Figures

F<sc>IG</sc>. 1.—
FIG. 1.—
Cladogram of relationships among representatives of 69 parrot genera and 8 outgroup taxa based on a strict consensus of 4 trees obtained from combined parsimony (MP) analysis of the 4 sequence partitions (COI + ND2, TROP, TGFB2, and RDPSN) with coded gaps. MP bootstrap support values for each node are shown above the branches with values of 100% indicated by asterisks; Bremer decay index values are shown below. The classifications of Rowley (1997) and Collar (1997) are indicated by bars on the right: I) family Cacatuidae, II) subfamily Loriinae, and, within the subfamily Psittacinae, the tribes a) Strigopini, b) Nestorini, c) Psittrichadini, d) Psittacini e) Arini, f) Psittaculini, g) Micropsittini, h) Platycercini, and i) Cyclopsittacini.
F<sc>IG</sc>. 2.—
FIG. 2.—
Phylogram of relationships among representatives of 69 parrot genera and 8 outgroup taxa based on Bayesian analysis of the 4 sequence partitions (COI + ND2, TROP, TGFB2, and RDPSN) and a fifth partition consisting of coded gaps from the 4 sequence partitions. Bayesian posterior probabilities ≥0.90 are indicated as percentages above the branches, values of 1.0 are indicated with an asterisk. The scale bar indicated the number of changes (base substitutions or changes in state of indel characters).
F<sc>IG</sc>. 3.—
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.

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