The Tuatara is the fastest-known Evolving Animal
A team of researchers have identified the rare Tuatara as the fastest evolving animal yet to be fully studied, at least at the molecular level.
The Tuatara (Sphenodon punctatus) belongs to an otherwise extinct reptilian group called the Rhynchocephalians. These reptiles are characterised by the presence of a beak-like upper jaw. Although the origin of this particular group of reptiles can be traced back to the early Triassic, just one genus (one species) remains today. To estimate the rate of evolution taking place within a species the research team studied DNA samples taken from ancient Tuatara remains dating from approximately 8,000 years ago and compared them to samples taken from living Tuatara.
The scientists found that although these little reptiles have remained largely unchanged physically over very long periods of evolution, they are evolving, at a molecular level faster than any other animal yet examined.
An Adult Male Tuatara
Picture Credit: New Zealand Tuatara Conservation Team
“What we found is that the Tuatara has the highest molecular evolutionary rate that anyone has measured,” commented researcher David Lambert from the Allan Wilson Centre for Molecular Ecology and Evolution in New Zealand.
Many scientists have hypothesised that molecular evolution would be fastest in animals whose physical form, or morphology, also evolved swiftly. The Tuatara findings dispute this, perhaps indicating that there is no relationship between the rate of molecular change and the rate of physical change in a species. This small reptile, now confined to a few small islands of the coast of New Zealand (but also recently introduced to the New Zealand mainland once again), closely resembles the extinct reptile Homoeosaurus which dates from the Early Jurassic (180 million years ago).
David Lambert and his team have studied molecular change in a number of animals, extinct and extant populations, including Adelie penguins, foxes, lions, horses and the Cave Bear (Ursus spelaeus). Of these animals, the Tuatara has a faster rate of DNA evolution. The information will assist scientists as they try to conserve this endangered species and provide guidance as to future areas of study. How helpful this rapid molecular evolution has been to the Tuatara genus has yet to be determined. These animals are reputed to be extremely long lived with estimated life spans of between 100 and 300 years.
The reason why the Tuatara has survived at all is more down to luck than judgement. These small lizard-like animals live in burrows and are relatively slow moving, their populations are soon overwhelmed if predatory mammals such as rats are introduced into their habitats. The fact that New Zealand was isolated from other land masses before land mammals become abundant probably resulted in the survival of this species, the speedy DNA of the Tuatara had nothing to do with this species survival.
The Tuatara remains severely threatened, this representative of an ancient reptile order cannot compete against introduced animals such as rats and cats. Indeed, even when these predators have been eliminated from the Tuataras few remaining strongholds, they may still face extinction. As global temperatures rise this is affecting the balance of males and female Tuataras being hatched from eggs. The warmer climate has meant that more eggs are hatching as males (temperature seems to be a determinant factor in deciding the sex of Tuatara offspring). Fewer females in the population could lead to a critical decline in the breeding population.
To read more about attempts to re-introduce the Tuatara to the New Zealand mainland: Living Fossil helped back to New Zealand mainland