A tiny native bird has challenged the theory that New Zealand’s ancient land mass was completely submerged millions of years ago.
DNA analysis of New Zealand wrens, just published in Molecular Phylogenetics and Evolution, has untangled the birds’ family history as well as a larger mystery around the very origins of New Zealand.
The research from the University of Adelaide focused on acanthisittids, a family of New Zealand wren species whose living members include the rock wren and the rifleman.
By studying the genetic differences between several of the wren species, including a number of now extinct birds, researchers were able to build an acanthisittid family tree, offering insights into when different birds branched off to become a new species.
“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,” says lead author Dr Kieren Mitchell, Postdoctoral Research Associate in the University’s Australian Centre for Ancient DNA.
Read more about the research on Scimex.org.
Re-floating Moa’s Ark?
The ancient species split is interesting in itself, but also offers some important clues for uncovering the truth about New Zealand’s geological past.
“Previously, researchers have suggested that New Zealand was completely submerged 21 to 25 million years ago,” say Mitchell, “which implies that all of New Zealand’s unique plants and animals must have immigrated and diversified more recently than that time.”
Proponents of this theory of ancient submergence, known as the Oligocene Drowning, argue “New Zealand’s present terrestrial fauna and flora evolved largely from fortuitous arrivals during the past 22 million years.”
The opposing ‘Moa’s Ark‘ view argues that parts of New Zealand’s land mass, Zealandia, must have been above sea-level and hosting terrestrial life ever since it started to break away from the ancient mega-continent Gondwanaland, over 80 million years ago.
Mitchell says the new wren findings don’t stack up with the Oligocene Drowning version of events.
“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.”
Featured image: The New Zealand Rockwren. Credit: Wikimedia / Andrew