Saturday, March 01, 2008

Rapid Evolution in Tuatara

Rapid molecular evolution in a living fossil. 2008. J. M. Hay et al. Trends in Genetics 24: 106-109.

From the press release:

In a study of New Zealand’s “living dinosaur” the tuatara has recovered DNA sequences from the bones of ancient tuatara 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 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.

“What we found is that the tuatara has the highest molecular evolutionary rate that anyone has measured,” Professor Lambert says.

“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.”

“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 too.”