Researchers of a new study find a 52-million-year-old Patagonian ancestor of a tree that was previously believed to only grow in the Northern Hemisphere. What was a rainforest tree doing in Patagonia?
Castanopsis is a currently living genus of trees that basically dominate the forests of Southeast Asia. It belongs to one of the most important plant families Fagaceae, which includes all beeches, oaks, stone oaks, allies, and chestnuts.
This tree family has always been considered Northern, not just because they are common in the Northern Hemisphere and in Southeast Asia, but also because the only place where they cross the equator is in Southeast Asia, and even then they only barely do so.
Castanopsis In The South
Now, however, a team of researchers has discovered 52-million-year-old evidence of Castanopsis in Patagonia. At first researchers hesitated to classify the leaves, but they later discovered fruit fossils that they were able to compare to living relatives. As it turns out, the fruits were from ancient Castanopsis that date back 52.2 million years ago during the Eocene Period.
“This is the first confirmed evidence that Fagaceae, considered restricted to the Northern Hemisphere, was in the Southern Hemisphere. This is remarkable and allows us to rethink the origins of the fossil flora,” said coauthor Maria Gandolfo of Cornell University.
At the time when that tree lived in Patagonia, it was globally warm and there was no polar ice. Back then, Australia, South America, and Antarctica had not yet broken off from the Gondwanan supercontinent, so animals probably helped spread the trees’ ancestors from North to South America. During that time, Patagonia still had wet rainforests before the trees were eventually displaced and the place turned into a shrubland.
Furthermore, after the breakup, it is also possible that the trees survived in Australia until it collided with Southeast Asia.
Castanopsis survived for millions of years, through changing climate and the breakup of Gondwana, but today they are being threatened by deforestation, development, crop cultivation, climate change, droughts, and fires. This is rather unfortunate because Castanopsis play a significant role in the dispersal of clean water to over half a billion people. Furthermore, many animals also rely on the trees, and losing them could have a significant impact on the lives of those animals and on biodiversity in general.
As can be seen in the ancient trees’ fate in Patagonia, they can go extinct in a place because of changes in climate and the environment, something that is currently going on at a much faster pace than it did millions of years ago.
The study is published in the journal Science.