Nature Diary
The Plant Tree of Life

How do plants differ from each other? Why are roses red and jasmines white? Why do some plants flower and some not at all? Understanding of the immense diversity of plant life is now rapidly improving because of advances in DNA sequencing tehnology. By comparing DNA sequences between different species, it is possible to identify changes (mutations) that accumulate over time. It is like finding fossils, but that are not in the Earth, but in the molecules of these plants. Put together, we can get what is called the tree of life.
Recently, an international team of 279 scientists led by the Royal Botanic Gardens, Kew, England, presented the most up-to-date understanding of the flowering plant tree of life. They used 1.8 billion letters of genetic code from the DNA of more than 9,500 species covering almost 8,000 known flowering plant genera, which is about 60% of all known species. Documenting this information sheds new light on the evolutionary history of flowering plants and their rise to ecological dominance on Earth. This will help to identify new species, uncover new medicinal compounds, and conserve plants in the face of climate change and biodiversity loss.
A key advantage of the team's approach is that it enables a wide diversity of plant material, old and new, to be sequenced, even when the DNA is badly damaged. The vast treasure troves of dried plant material in the world's herbarium collections, which comprise nearly 400 million scientific specimens of plants, can now be studied genetically.
The team even analyzed extinct plants, such has the Guadalupe Island olive (Hesperelaea palmeri), which has not been seen alive since 1875. In fact, 511 of the species sequenced are already at risk of extinction, according to the IUCN Red List, including three more like Hesperelaea that are already extinct.
Across all 9,506 species sequenced, more than 3,400 came from material sourced from 163 herbaria in 48 countries. Additional material from plant collections around the world (e.g., DNA banks, seeds, living collections) have been vital for filling key knowledge gaps to shed new light on the history of flowering plant evolution. The team also benefited from publicly available data for more than 1,900 species, highlighting value of the open science approach to future genomic research.

Darwin's Mystery
Flowering plants alone account for about 90% of all known plant life on land and are found virtually everywhere on the planet—from the steamiest tropics to the rocky outcrops of the Antarctic Peninsula. We do not understand how these plants came to dominate the scene soon after their origin; even Charles Darwin was mystified.
Utilizing 200 fossils, the authors found that early flowering plants did indeed explode in diversity, giving rise to more than 80% of the major lineages that exist today shortly after their origin.
However, 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 will surely help today's scientists grappling with the challenges of understanding how and why species diversify.
The tree of plant life and all of the data have been made openly and freely accessible to both the public and scientific community. Open access will help scientists to make the best use of the data, such as combining it with artificial intelligence to predict which plant species may include molecules with medicinal potential. Similarly, the tree of life can be used to better understand and predict how pests and diseases are going to affect the plants of the U.K. in the future. Ultimately, the authors note, the applications of this data will be driven by the ingenuity of the scientists accessing it.