Environment Australian origin likely for iconic New Zealand tree

Australian origin likely for iconic New Zealand tree

Ancestors of the iconic New Zealand Christmas Tree, Pōhutukawa, may have originated in Australia, new research from the University of Adelaide suggests.

Two new fossil species of Metrosideros, the scientific name for Pōhutukawa and related species, have been found near St Helens, Tasmania. The fossils are about 25 million years old.

Researcher Mylall Tarran, PhD candidate in the University of Adelaide’s School of Biological Sciences, says the Pōhutukawa is one of New Zealand’s most iconic flowering plants and is of particular significance in Maori culture.

“It is also one of, if not the, most widely spread flowering plant groups in the Pacific. It grows in Hawaii, Papua New Guinea, New Caledonia, Tahiti, the Bonin Islands near Japan, on sub-Antarctic islands, and many other islands in between, as well as having single representatives in Africa and South America,” he says.

But surprisingly, considering the species’ unique and highly effective seed dispersal biology, Pōhutukawa is not found in Australia.

In fact, Australia is the only major vegetated landmass in the Southern Hemisphere where Metrosideros does not occur today, although previous work has shown that the genus did occur here some 35-40 million years ago.

“This new research, which identifies two new fossil species of Metrosideros from Tasmania from about 25 million years ago, shows that a diversity of the trees once grew in Australia,” Mr Tarran says.

“But these more recent fossils belong to a subgenus of Metrosideros that is less widely distributed than the earlier fossils, mainly in areas that were part of the great supercontinent Gondwana.

“These species may not have been as well adapted for long-distance dispersal as those other species, and so it is likely that they originated here,” he says. “The question still remains as to why they became extinct in Australia.”

Mr Tarran’s research has been supervised by Professor Bob Hill, Executive Dean of the Faculty of Sciences at the University of Adelaide, and Dr Peter Wilson, a Principal Research Scientist at the Royal Botanic Gardens Sydney, in collaboration with Associate Professor Greg Jordan, University of Tasmania, and Honorary Associate Professor Mike Macphail, Australian National University.

Read more about these fossil discoveries here. Story credit: University of Adelaide newsroom.

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