Why would a study on flowers and plants be hailed as an "incredible achievement"?
An international team of 279 scientists led by the Royal Botanic Gardens, Kew, unveiled the latest understanding of the evolutionary tree of flowering plants in a new paper published in the journal Nature on April 24.
This research, utilizing 1.8 billion genetic codes from over 9,500 species, covering nearly 8,000 known genera of flowering plants (about 60%), unveils a botanical evolutionary history for humanity, revealing how these plants rose to dominate Earth's ecosystems.
Building the evolutionary tree of angiosperms involves sequencing data that is 15 times more extensive than similar studies, covering over 9,500 different flowering plant species.
Image Source: Royal Botanic Gardens, Kew
Researchers believe that this valuable data will aid in identifying new species, refining plant classification, discovering new medicinal compounds, and protecting plants in the face of climate change and biodiversity loss.
"Unlocking" historical plant specimens
Similar to a human family tree, the phylogenetic tree of flowering plants helps us understand the relationships between different species. By comparing DNA sequences of different species to unveil the evolutionary tree, researchers can identify changes (mutations) accumulated over time, akin to deciphering "molecular fossils."
Advancements in DNA sequencing technologies have significantly enhanced our understanding of evolutionary trees. In this study, the team developed new genomic techniques capable of extracting hundreds of genes and hundreds of thousands of genetic code letters from each sample, representing an order of magnitude increase over earlier methods.
The oldest plant sequenced in this study is a dried plant specimen collected in 1829.
Image Source: Royal Botanic Gardens, Kew
A key advantage of the new method is its ability to sequence a wide range of both new and old plant materials even when the DNA is severely damaged. Plant herbaria around the world are vast repositories of dried plant materials, including nearly 400 million botanical specimens, holding a wealth of evolutionary information.
The first sequenced specimen of Alstonia spectabilis in research, a species of significant medicinal value to the indigenous Dèdōng people.
Image Source: Royal Botanic Gardens, Kew
For instance, the team was able to sequence a sample of sandalwood collected in Nepal nearly 200 years ago, despite its poor DNA quality, and place it in the phylogenetic tree.
Furthermore, they analyzed extinct plants, such as the Guadalupe Island olive. In fact, according to the International Union for Conservation of Nature (IUCN) Red List of Threatened Species, 511 of the species sequenced in this study are already at risk of extinction.
Among the 9,506 species sequenced, over 3,400 species come from 48 countries and 163 herbaria, with others sourced from plant collections worldwide, including DNA banks, seeds, and living collections. These are crucial for filling key knowledge gaps and understanding the evolutionary history of flowering plants.
Unraveling the mystery that puzzled Darwin
Flowering plants originated over 140 million years ago, rapidly outcompeting other vascular plants to make up around 90% of all known land plants.
However, several generations of scientists, including Charles Darwin, have been puzzled by this: why did these plants dominate shortly after their origin?
Scientists have sequenced the parasitic plant Pilostyles aethiopica, which lives inside other plants and is only visible when it flowers. DNA sequencing has led to a reclassification of the group to which this plant belongs.
Image Source: Sidonie Bellot/Royal Botanic Gardens, Kew
In response to the seemingly sudden appearance of diversity in the fossil record, Darwin wrote to his close friend and Royal Botanic Gardens director Joseph Hooker in 1879: "We are at our wit's end to understand how all the higher plants of the present day have been developed."
Now, a research team has scaled their evolutionary tree over time using 200 fossils, revealing how flowering plants evolved during different geological periods. They found that the diversity of early flowering plants did indeed undergo explosive growth, giving rise shortly after their origin to over 80% of the major lineages present today.
The new evolutionary tree has reclassified the Pineapple Lily family and genus, which is a tropical small tree with peculiar fruit. Image source: Danilo Tandang.
However, this trend steadily declined over the next 100 million years until about 40 million years ago when biodiversity surged again, coinciding with a global temperature drop. These new insights help today's scientists understand how species have responded to diverse challenges.
Openly sharing the "fruit" of the evolutionary tree
Constructing the evolutionary tree of flowering plants is of significant importance to biodiversity research. Just as one can predict the properties of an element based on its position in the periodic table, the position of a species in the evolutionary tree can help predict its attributes. Therefore, the new data contained in the evolutionary tree contributes to advancements in various scientific fields.
Among the data used in this study, over 1,900 species were previously publicly available, highlighting the value of open scientific methods in genomic research.
Further opening up the data will assist scientists in fully utilizing these research findings in the future, such as integrating them with artificial intelligence (AI) to predict which plant species may contain medicinal molecules. Similarly, it can help scientists better understand plant diseases and predict the impact they may have on plants in the future.
Researchers have stated that AI has been used to predict which plants contain chemical substances with the potential to treat malaria. The newly constructed evolutionary tree of flowering plants contains a vast dataset, providing opportunities for making more accurate predictions and speeding up the discovery of drugs from plants to cure challenging diseases.
