0829 GMT October 23, 2019
Newly discovered fossils suggested the evolutionary origins of the tree and its relatives lie in Australia, UPI wrote.
The evergreen species, Metrosideros excelsa, also known as the iron tree, is most associated with New Zealand, but it is found throughout the Pacific.
Myall Tarran, a doctoral candidate in the University of Adelaide's School of Biological Sciences, said, "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.”
Surprisingly, the tree isn't found in Australia.
The tree's seeds are light but hardy, able to be carried by gentle winds while surviving freezing temperatures and prolonged exposure to salt water.
Tarran said, "This makes it hard to pin down where the genus might have originated.
"Metrosideros seems to have achieved most of its present distribution relatively recently through dispersal."
Scientists have previously uncovered Metrosideros fossils in Australia — proof that the iron tree relatives once grew in Australia but went extinct.
The newest fossils suggest several Metrosideros species once grew in Australia.
The newly discovered species belong to a different subgenus than that of the New Zealand Christmas tree.
Researchers said seeds from this subgenus weren't as easily dispersed, which suggested the genus may have originated in Australia.
Tarran added, "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.”
The findings — detailed in the American Journal of Botany — suggested the Metrosideros genus diversified on Australia before traveling throughout the Pacific islands.
Tarran said, "The question still remains as to why they became extinct in Australia.”