Almost every plant we eat has flowers, and flowering plants live in every corner of the earth. But many questions remain about when and how this huge group emerged in the history of life on Earth.
After a heroic DNA sequencing effort, hundreds of scientists have collaborated to create a new family tree of flowering plants. Scientists compared the genetic sequences of more than 9,500 species, many of them dried specimens preserved in museums, and sketched key junctures in the evolution of flowering plants. In a study published in April in the journal Nature, they presented data showing that more than 80 percent of today's major flowering plant lineages stemmed from a sudden invention that began in the late Jurassic period, about 150 million years ago. This suggests that it originates from.
Previous plant evolutionary trees constructed by scientists have often used the genome of chloroplasts, the organelles that enable plants to carry out photosynthesis. These genomes could potentially be sequenced using older methods. But scientists were not convinced that the patterns they showed were the same as those that might be revealed by the plants' primary genomes, which are stored in the nucleus of cells and are more difficult to study.
Then, five years ago, another scientific collaboration published detailed information about the nuclear genomes of more than 1,100 plant species. This has enabled the team behind the Nature paper to design a new tool for sequencing the nuclear genes of a wide variety of flowering plants, says the team behind the Nature paper, leaders of the Kew Gardens Tree of Life Initiative, and a new paper. William Baker, author of
Although they used the tools on live plants, the research team also contacted institutions in 48 countries with dry plant collections to obtain samples of rare specimens. Four of the plants included in the analysis are already extinct. Olives from Guadalupe IslandUltimately, the research team used data from about 60 percent of all modern plant genera.
When they assembled a new evolutionary tree, they found that many of the relationships suggested by the chloroplast-based tree were confirmed. But there were also surprises. New data has reorganized the relationships of many plant groups and reclassified some individual species.
One of the discoveries that surprised plant experts involves a group of flowers that are so common that we often take them for granted. The Asteraceae family, which includes daisies and sunflowers, did not fit into the new evolutionary tree as the researchers had hoped. The researchers found that the connections between daisies and surrounding flower families changed depending on how the new data was used to construct the tree.
“Previously, when we found similar results, we blamed it on a lack of data,” said Kew Gardens biologist and study author Alexandre Zuntini.
But these anomalies in the natural history of flowers cannot be easily ignored now that data are not as scarce as they once were. No one can say what caused the anomaly, but Dr Zuntini said one possibility is that a more rapid or more promiscuous evolution of the flower's branches was occurring at the time. It suggests that there is.
The researchers also attempted to relate the evolutionary tree to known geological time periods. The network of relationships represented by DNA does not itself contain dates. So it's difficult to say how many years ago the pair of species began to diverge.
However, many flowering plants have been found as fossils and can be dated. The research team used 200 flower fossils to add dates to the genealogy, showing the diversity of flowering plants from the Late Jurassic to Early Cretaceous period, when dinosaurs lived, starting about 150 million years ago. It was determined that there had been a major explosion. This confirms estimates made in the past, Dr. Baker said. The new trees suggest that species numbers surged again about 40 million years ago as global temperatures plummeted.
The research team is sharing their sequencing tools and hopes other researchers can make use of them. Baker also hopes to add more species to this evolutionary tree in the future, as more data means looking at higher resolution to see what happened in the past. the doctor said. Little by little, each petal reveals the history of flowering plants.