Discovering a Revolutionary Tree of Flowering Plants Just in Time for Spring
Through massive data sequencing, hundreds of researchers have discovered new information about the evolution of flowers on Earth.
There are flowers on almost every plant that we consume, and there are flowers on every continent. However, a lot of unanswered questions surround the origins and evolution of this enormous group across the course of life on Earth.
A new flowering plant family tree has been developed by hundreds of scientists working together following an incredible effort to sequence DNA. Through the analysis of DNA sequences from over 9,500 species, many of which are dried specimens conserved in museums, researchers have identified significant divergencies in the history of flowering plant life. The findings presented in a study that was published in the journal Nature in April implies that over 80 percent of the major lineages of flowering plants that exist today originated in a dramatic creative explosion that started in the late Jurassic Period, some 150 million years ago.
Scientists have previously constructed evolutionary trees of plants using the DNA of the chloroplast, the organelle responsible for photosynthesis in plants. Older techniques could be used to sequence these genomes. However, the patterns they displayed could not be guaranteed to match those that the plant's primary genome, which is contained in the nucleus of the cell and more challenging to examine, might disclose.
Then, five years ago, a different research team released comprehensive data regarding the nuclear genomes of over 1,100 plant species. William Baker, the director of the Kew Gardens Tree of Life Initiative and one of the authors of the Nature publication, explained that this made it possible for the team to create new instruments for sequencing nuclear genes from a vast array of flowering plants.
In addition to using the instruments on live plants, the researchers contacted organisations in 48 different nations that had collections of dried plants in order to obtain samples of uncommon types. A dried sprig from 1875 was used to sequence the genome of the Guadalupe Island olive, one of the four species included in the analysis that is already extinct. Ultimately, the group incorporated information from roughly 60% of all extant plant genera.
Upon assembling the new evolutionary tree, scientists
discovered that it validated numerous links inferred by trees constructed using
chloroplasts. Still, there were some surprises: Several plant group
relationships were rearranged in light of the new information, and some individual
species underwent new classifications.
One study about a group of flowers that are so commonplace that it's easy to take them for granted has astonished plant experts. The family Asteraceae, which includes sunflowers and daisies, did not fit into the new evolutionary tree as the researchers had anticipated. Researchers discovered that the daisies' connections to neighbouring flower families would change depending on how the new data was utilised to construct the tree.
"Previously, when comparable outcomes were discovered,
we utilised to attribute the fault to insufficient data," stated Alexandre
Zuntini, a scientist at Kew Gardens and a co-author of the research.
However, these oddities in the natural history of flowers cannot be simply
discounted given that data is less sparse than it formerly was. Although the
reason for the anomaly remains unknown, Dr. Zuntini proposes that it could have
been due to the faster or more chaotic evolution of that particular flower
branch at that particular period.
Additionally, the researchers attempted to connect known geological eras to their evolutionary tree. There are no dates in the network of relationships that the DNA alone displays. Therefore, it is difficult to determine the exact age at which two species started to diverge.
However, fossils of numerous blooming plants have been found, and they may be dated. The researchers detected a massive expansion in flowering plant diversity in the Late Jurassic and Early Cretaceous periods, when dinosaurs lived, beginning about 150 million years ago, using 200 fossilised flowers to add dates to the genealogy. This validates previous calculations, according to Dr. Baker. According to the new tree, there was another spike in species diversity around 40 million years ago, coinciding with a sharp decline in global temperatures.
The group is making their sequencing tools available to other researchers in the hopes that they may be useful. According to Dr. Baker, they also intend to add more species to this evolutionary genealogy in the future because more data allows for a more detailed examination of historical events. Petal after petal, the history of flowering plants is becoming more and more clear.