By Will Dunham
WASHINGTON (Reuters) – Flowering plants – from corn, wheat, rice and potatoes to maple, oak, apple and cherry trees, as well as roses, tulips, daisies and dandelions and even the corpse flower and the voodoo lily – are cornerstones of Earth’s ecosystems and essential to humanity.
New research based on genome data from 9,506 species, as well as the examination of 200 fossils, provides the deepest understanding to date of the evolutionary history of flowering plants called angiosperms – the largest and most diverse group of plants. It details how angiosperms appeared and became dominant during the age of dinosaurs and how they changed over time.
Scientists have created a new tree of life for angiosperms, covering 15 times more types of flowering plants – nearly 60% of them – than the closest comparable study.
“It’s a huge advance in our understanding of plant evolution,” said botanist William Baker of the Royal Botanic Gardens, Kew (RBG Kew) in London, senior author of the research published Wednesday in the journal Nature.
Angiosperms, plants that produce flowers and generate their seeds in fruits, comprise around 330,000 species and comprise around 80% of the world’s plants. They include, among others, all major food crops, grasses, most broad-leaved trees, and most aquatic plants. Their closest relatives are the gymnosperms, a group that preceded them on Earth and includes conifers and some others, with just over 1,000 species.
The study identified two pulses of diversification among angiosperms. The first occurred about 150-140 million years ago, early in their existence during the Mesozoic era, with 80% of the major angiosperm lineages emerging during this period. The next one happened about 100 million years later, during the Cenozoic era, after the disappearance of dinosaurs and the rise of mammals, amid decreasing global temperatures.
“Angiosperms have many structural adaptations that confer advantages over gymnosperms, but chief among them are those that contribute to reproductive success,” Baker said.
Gymnosperms and angiosperms have seeds, but flowering plants contain seeds that protect them from dehydration and allow them to thrive in a wider range of environments, from the tropics to deserts to Antarctica.
They also developed the flower, a structure that allowed them to establish relationships with pollinating animals, especially insects, while gymnosperms generally depend on the wind for pollination. Angiosperms have developed a great diversity of fruit types, allowing for effective seed dispersal.
“With these innovations, angiosperms became invincible,” Baker said.
Charles Darwin, the 19th-century British naturalist and architect of evolutionary theory, was surprised by how flowering plants appeared on the scene in the Mesozoic fossil record.
In an 1879 letter to Joseph Hooker, then director of RBG Kew, Darwin wrote that “the rapid development, so far as we can judge, of all the higher plants in recent geological times is an abominable mystery.”
“Remarkably,” Baker said, “we were able to use the ‘molecular fossil record,’ the accumulated change in DNA over time, to see real evidence of this explosion happening in early angiosperms.”
Flowering plants provide most of the calories consumed by humans – grains, fruits and vegetables – including indirectly as livestock feed. They also enchanted people with their beauty – fields of sunflowers, bouquets of roses, clusters of calla lilies – and their pleasant scent.
“They are sources of many of our medicines and contain potential solutions to global challenges such as climate change, biodiversity loss, human health, food security and renewable energy,” Baker said.
The study could help scientists better understand disease and pest resistance in angiosperms and navigate potential new medicinal uses – for example, to combat malaria.
“Combining the tree of life with extinction risk assessments for each lineage allows us to prioritize lineages for conservation based on their uniqueness,” said Alexandre Zuntini, a botanist at RBG Kew and lead author of the study. “This is extremely important for humanity, as these lineages may contain chemical compounds or even genes that could be useful for the survival of our species.”
(Reporting by Will Dunham, Editing by Rosalba O’Brien)
