Dinosaur Extinction Grounded Ancient Birds, New Research Finds
ScienceDaily (Jan. 26, 2010) — An abundance of food and lack of predators following the extinction of dinosaurs saw previously flighted birds fatten up and become flightless, according to new research from The Australian National University.
Emus. New research suggests that ancestors of the African ostrich, Australasian emu plus cassowary, South American rheas and New Zealand moa became flightless independently, in close association with the extinction of the dinosaurs about 65 million years ago. (Credit: iStockphoto/John Carnemolla)
Their molecular dating study suggests that the ancestors of the African ostrich, Australasian emu plus cassowary, South American rheas and New Zealand moa became flightless independently, in close association with the extinction of the dinosaurs about 65 million years ago.
...
+++++
Systematic Biology 2010 59(1):90-107; doi:10.1093/sysbio/syp079
Tinamous and Moa Flock Together: Mitochondrial Genome Sequence Analysis Reveals Independent Losses of Flight among RatitesMatthew J. Phillips1,*, Gillian C. Gibb2, Elizabeth A. Crimp2 andDavid Penny2
1 Centre for Macroevolution and Macroecology, School of Botany and Zoology, Research School of Biology, Australian National University, Canberra, ACT 0200, Australia
2 Allan Wilson Center and Institute of Molecular BioSciences, Massey University, Palmerston North, New Zealand
* Correspondence to be sent to: Centre for Macroevolution and Macroecology, Research School of Biology, Australian National University, Gould Building, Canberra, ACT 0200, Australia; E-mail: matt.phillips@anu.edu.au.
Abstract
Ratites are large, flightless birds and include the ostrich, rheas, kiwi, emu, and cassowaries, along with extinct members,such as moa and elephant birds. Previous phylogenetic analyses of complete mitochondrial genome sequences have reinforced the traditional belief that ratites are monophyletic and tinamous are their sister group. However, in these studies ratite monophyly was enforced in the analyses that modeled rate heterogeneity among variable sites. Relaxing this topological constraint results in strong support for the tinamous (which fly) nesting within ratites. Furthermore, upon reducing base compositional bias and partitioning models of sequence evolution among protein codon positions and RNA structures, the tinamou–moa clade grouped with kiwi, emu, and cassowaries to the exclusion of the successively more divergent rheas and ostrich. These relationships are consistent with recent results from a large nuclear data set, whereas our strongly supported finding of a tinamou–moa grouping further resolves palaeognath phylogeny. We infer flight to have been lost among ratites multiple times in temporally close association with the Cretaceous–Tertiary extinction event. This circumvents requirements for transient microcontinents and island chains to explain discordance between ratite phylogenyand patterns of continental breakup. Ostriches may have dispersed to Africa from Eurasia, putting in question the status of ratites as an iconic Gondwanan relict taxon.
Keywords: Base composition; flightless; Gondwana; mitochondrial genome; Palaeognathae; phylogeny; ratites
Received January 19, 2009; Revised April 20, 2009; Accepted October 14, 2009
Associate Editor: Adrian Paterson
+++++
