March 24, 2008 -- New DNA research has questioned previous notions about the evolution of the tuatara
In
a study of New Zealand's "living dinosaur" the tuatara, evolutionary
biologist, and ancient DNA expert, Professor David Lambert and his team
from the Allan Wilson Centre for Molecular Ecology and Evolution
recovered DNA sequences from the bones of ancient tuatara, which are up
to 8000 years old. They found that, although tuatara have remained
largely physically unchanged over very long periods of evolution, they
are evolving - at a DNA level - faster than any other animal yet
examined. The research will be published in the March issue of Trends
in Genetics.
"What we found is that the tuatara has the highest molecular
evolutionary rate that anyone has measured," Professor Lambert says.
The
rate of evolution for Adélie penguins, which Professor Lambert and his
team have studied in the Antarctic for many years, is slightly slower
than that of the tuatara. The tuatara rate is significantly faster than
for animals including the cave bear, lion, ox and horse.
"Of
course we would have expected that the tuatara, which does everything
slowly - they grow slowly, reproduce slowly and have a very slow
metabolism - would have evolved slowly. In fact, at the DNA level, they
evolve extremely quickly, which supports a hypothesis proposed by the
evolutionary biologist Allan Wilson, who suggested that the rate of
molecular evolution was uncoupled from the rate of morphological
evolution."
Allan Wilson was a pioneer of molecular evolution.
His ideas were controversial when introduced 40 years ago, but this new
research supports them.
Professor Lambert says the finding will
be helpful in terms of future study and conservation of the tuatara,
and the team now hopes to extend the work to look at the evolution of
other animal species.
"We want to go on and measure the rate of
molecular evolution for humans, as well as doing more work with moa and
Antarctic fish to see if rates of DNA change are uncoupled in these
species. There are human mummies in the Andes and some very good
samples in Siberia where we have some collaborators, so we are hopeful
we will be able to measure the rate of human evolution in these animals
too."
The tuatara, Sphendon punctatus, is found only in New
Zealand and is the only surviving member of a distinct reptilian order
Sphehodontia that lived alongside early dinosaurs and separated from
other reptiles 200 million years ago in the Upper Triassic period.
Source : Cell Press
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