Australasian Science: Australia's authority on science since 1938

Wren DNA Reshapes NZ Geological Theory

A DNA analysis of living and extinct species of wrens may change theories concerning New Zealand’s geological and evolutionary past, including the possibility that New Zealand wasn’t completely submerged under the ocean 21–25 million years ago.

Acanthisittid wrens are a group of tiny, largely flightless birds found nowhere else in the world. While they are similar in appearance and behaviour to true wrens, they don’t belong to the same family.

“Of the seven species living before humans arrived in New Zealand, only two now remain: the rock wren and the rifleman,” says Dr Kieren Mitchell of the University of Adelaide’s Australian Centre for Ancient DNA. “Consequently, little is known about their evolution.”

The study led by Mitchell, published in Molecular Phylogenetics and Evolution, analysed DNA from three of the extinct species and two living species. “Most surprisingly, we found that some of the wren species were only distantly related to each other, potentially sharing a common ancestor over 25 million years ago,” he says.

“Previously, researchers have suggested that New Zealand was completely submerged 21–25 million years ago, which implies that all of New Zealand’s unique plants and animals must have immigrated and diversified more recently than that time.

“This theory is consistent, for instance, with what is known about the moa, where the different species all shared a common ancestor much more recently than 21 million years ago.

“But the ancient divergences we found among the wrens suggest that they have been resident in New Zealand for more than 25 million years, and possibly as long as 50 million years (when New Zealand became disconnected from the rest of Gondwana). As the wrens were largely very poor fliers, or even flightless, some land must have remained throughout that period.

“This has important consequences for our understanding of the evolution of New Zealand’s unique ecosystems,” Mitchell says.