ANU
Media Release
News
from The Australian National University
THURSDAY 21 JANUARY 2010
DINOSAUR EXTINCTION GROUNDED ANCIENT BIRDS
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.
The study, led by Dr Matthew Phillips, an ARC
Postdoctoral
Fellow at the ANU Research School of Biology, looked at the
mitochondrial
genome sequences of the now-extinct giant moa birds of New Zealand. To
their
surprise, the researchers found that rather than having a flightless
relative,
their closest relatives are the small flying tinamous of South America.
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.
“Many of the world’s largest flightless birds,
known as
ratites, were thought to have shared a common flightless ancestor. We
followed
up on recent uncertainty surrounding this assumption,” said Dr Phillips.
“Our study suggests that the flighted ancestors of
ratites
appear to have been ground-feeding birds that ran well. So the
extinction of
the dinosaurs likely lifted predation pressures that had previously
selected
for flight and its necessary constraint, small size. Lifting of this
pressure
and more abundant foraging opportunities would then have selected for
larger
size and consequent loss of flight.”
The finding of independent origins of
flightlessness also
solves a mystery of how these flightless birds dispersed across the
world over
marine barriers – their ancestors flew.
“Ratite birds have been thought of as relics of
the former
Gondwanan supercontinent, which combined Africa, South America,
Australia,
Antarctica, New Zealand, India and Madagascar,” said Dr Phillips.
“Not only have we shown that the separate ratite
lineages
evolved too recently to have been on Gondwana before its continents
drifted
apart, but from our analyses we infer that at least ostriches, and
possibly
ratites as a whole, have their origins in the northern continents.”
The researchers’ paper, Tinamous and Moa Flock
Together:
Mitochondrial Genome Sequence Analysis Reveals Independent Losses of
Flight
among Ratites, is published in this month’s issue of the journal Systematic
Biology.
For interviews:
Dr Matthew Phillips: 02 6125 9138
For media assistance:
Martyn Pearce, ANU Media: 02 6125 5575 / 0416
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