The pink lapacho tree is one of about 300,000 species of flowering plants
Roberto Tetsuo Okamura/Shutterstock
Botanists have mapped the evolutionary relationships between flowering plants using genomic data from more than 9500 species. The newly compiled tree of life will help scientists piece together the origins of flowering plants and inform future conservation efforts.
Around 90 per cent of land-dwelling plants are ones that flower and bear fruit, called angiosperms. These flowering plants are essential in maintaining Earth’s ecosystems, such as by storing carbon and producing oxygen, and make up the bulk of our diets.
“Our very existences are dependent on them,” says William Baker at the Royal Botanic Gardens, Kew, in the UK. “That’s why we really need to understand them.”
For the past eight years, Baker and his colleagues have been working on completing trees of life that describe the evolutionary relationships between all genera of plants and fungi.
Starting with flowering plants, the team designed molecular probes to search for 353 specific genes that can be found in the nuclei of all angiosperms. “The nuclear genome is humongous,” says Baker. “So we had to focus on a certain set of genes.”
So far, the researchers have sequenced the genes of 9506 species of flowering plants, mainly using specimens from collections around the world and public databases. This represents nearly all known angiosperm families and around 8000 of the 13,400 recorded genera. Some of the specimens sampled in the analysis are more than 200 years old, including a sandwort called Arenaria globiflora, and many came from extinct species, such as the Guadalupe Island olive (Hesperelaea palmeri).
By comparing similarities in the gene sequences of each flowering plant, the researchers were then able to figure out where they sat on the tree of life.
It is the most comprehensive look at angiosperms to date, says Baker. “We often liken it to the periodic table of elements,” he says. “It’s the fundamental framework for life.”
The angiosperm tree of life
Royal Botanical Gardens Kew
After their emergence around 140 million years ago, angiosperms quickly flourished, surpassing the flowerless gymnosperms as the world’s dominant plant type. The abrupt appearance of flowering plant diversity in the fossil record has stumped scientists for the past few centuries, with Charles Darwin calling it an “abominable mystery”.
Now, the tree of life confirms that around 80 per cent of major flowering plant lineages that are still around today were part of this early boom in angiosperm diversity. “We can’t say we’ve solved this ‘abominable mystery’, but we can at least say that there really is one,” says Baker.
The tree of life also sheds light on another surge in diversity that occurred around 40 million years ago, which was probably triggered by a drop in global temperatures at the time.
In future, the tree of life could also aid in the search for plants with pharmaceutical properties for new medicines, says Ilia Leitch, another member of the team at Kew. It can also help scientists identify new species and assess which ones may be the most vulnerable to climate change.
“This is the latest and greatest evolutionary framework from which to conduct new studies, getting closer to the mechanisms that allowed flowering plants to take over the globe,” says Ryan Folk at Mississippi State University.
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