Underground trees are almost entirely buried and can live for more than 10,000 years in the savannahs of southern Africa and South America, but how did they evolve?
Savannas generally have widely spaced trees growing amongst grassland. For many years, researchers have generated different hypotheses about how they came to be, such as from human deforestation, a change in temperature or because trees don’t cope well with arid conditions. Most of these theories have been disproven.
An article on the BBC website looks at recent research which suggests savannahs were born from wildfire which also caused trees to adapt to growing underground. While grasses can easily live with fire because they quickly re-sprout, fire can be catastrophic for trees.
“Some underground trees grow large woody structures as much as one metre wide, while others form branched networks of stems measuring up to 10 metres across. Their shoots are so small and thin that it makes little difference to the tree if it occasionally loses them to wildfire - they can quickly regrow.”
The article goes on to explain the research which analyzed the DNA of 1400 different woody species in southern Africa, including about 50 of the 200 known underground tree species that grow there. This made it possible to determine how each species related to each other and generate “an evolutionary tree of trees” and the origins of each species.
The results show that underground trees evolved quite recently (less than 8 million years ago) but not all at once. At least 30 different types of tree adopted the strategy independently.
Read the full story: Why some trees evolved to live underground