Scientists have developed an evolutionary tree that shows when plants developed specific adaptations to cold.
Published in Nature, researchers at Macquarie University, Sydney [See Zanne et al. Nature. doi:10.1038/nature12872. – 2013] have identified 3 main adaptations by plants to extreme cold, and also the order of these evolutionary events:
1. plants would drop their leaves each cold season
2. plants made skinnier water-conducting pathways, allowing them to keep their leaves while reducing the risk of air bubbles developing during freezing and thawing, which would shut down those pathways (the fatter the pathways, the higher the risk)
3. plants died down completely during cold seasons, losing aboveground stems and leaves and retreating as seeds like tomato, or storage organs like bulbs and tubers underground, such as tulip and dahlia.
Most often woody plants became herbs or developed skinnier pathways before moving into freezing climates. In contrast, plants usually began dropping their leaves after moving into freezing climates.
The new ‘evolutionary tree’ contains 32,223 species of plants, allowing scientists to model changing climates and corresponding plant adaptations.
“Understanding the processes that shaped biodiversity millions of years ago is hard because we can’t run experiments or even directly observe what plants and communities looked like then,” said Macquarie University researcher, Richard Fitzjohn.
“The new evolutionary tree and statistical approaches we developed allow us some insight into this deep past.”
Read more at Nature