Scientists unveil genomic 'tree of life' for flowering plants

An international team of 279 scientists from 138 organisations, led by the Royal Botanic Gardens, Kew, has produced a genomic ‘tree of life’ for flowering plants (angiosperms), revealing how the different species of plants relate to one another. Published in the journal Nature, the genomic tree is understood to be the most comprehensive of its kind ever made, shedding new light on the evolutionary history of flowering plants and their rise to ecological dominance on Earth.

About 140 million years ago, there was an explosion in the existence of flowering plants on Earth. They quickly overtook other vascular plants, including their non-flowering, closest living relatives like conifers, cycads and ginkgos (gymnosperms), and today account for about 90% of all known plant life on the planet. Charles Darwin was particularly mystified by the seemingly sudden appearance of such diversity in the fossil record, calling it an “abominable mystery”.

By comparing DNA sequences of different species and seeing their changes over time, scientists can better understand the complex history of their evolution. Using 1.8 billion letters of genetic code from over 9500 species covering almost 8000 known flowering plant genera, the international team has now presented the most up-to-date understanding of flowering plants, which will help with everything from classifying and identifying new species to discovering new medicines.

The study used new genomic techniques to magnetically capture hundreds of thousands of letters of genetic code from every sample; this enabled a wide diversity of plant material, old and new, to be sequenced, even when the DNA was badly damaged. The team even analysed extinct plants, some of which have not been seen alive since the 19th century, by sequencing preserved plant material from herbaria across the world. The team also benefited from publicly available data for over 1900 species, and analysed over 200 fossils to scale the tree to a timeline.

The extinct Guadalupe Island olive (Hesperelaea palmeri), which has not been seen alive since 1875, was sequenced from dried plant material. Image ©RBG Kew.

“This extraordinary global effort provides unprecedented access to plant data dating all the way back to the late Jurassic period,” said Dr Hervé Sauquet, Head of Plant Discovery and Evolution Research at the Botanic Gardens of Sydney.

“We now know early flowering plants did indeed explode in diversity in the Early Cretaceous, giving rise to over 80% of the major lineages that exist today,” Sauquet continued. This trend then declined to a steadier rate for the next 100 million years until another surge in diversification about 40 million years ago, coinciding with a global decline in temperatures. These new insights can help today’s scientists understand how and why species diversify.

All in all, the work contains 15 times more data than any comparable studies of the flowering plant tree of life, as well as 800 plants that have never had their DNA sequenced before. The sheer amount of data unlocked by this research, which would take a single computer 18 years to process, is a huge stride towards building a tree of life for all 330,000 known species of flowering plants.

“Analysing this unprecedented amount of data to decode the information hidden in millions of DNA sequences was a huge challenge,” said Dr Alexandre Zuntini, a Research Fellow at Kew. “But it also offered the unique opportunity to re-evaluate and extend our knowledge of the plant tree of life, opening a new window to explore the complexity of plant evolution.”

Like the periodic table, the location of a species in the tree of life means we can predict its properties. Scientists can use the tree to understand how pests and diseases are going to affect plants in the future, for example, or assess which plant species may include molecules with medicinal potential. The tree is now accessible to both the public and scientific community through the Kew Tree of Life Explorer at https://treeoflife.kew.org/.

Top image: The new ‘tree of life’ of flowering plants. Image ©RBG Kew.