A new study conducted by researchers from the University of Bath illustrates that flowering plants escaped relatively unharmed from the mass extinction that killed the dinosaurs 66 million years ago. While they suffered some species loss, the devastating event helped flowering plants become the dominant type of plant they are today.
Numerous mass extinctions have occurred throughout Earth's history, the most famous caused by an asteroid (小行星) hit 66 million years ago. The Cretaceous-Paleogene (K-Pg) extinction event wiped out at least 75% of all species on Earth, including the dinosaurs, but until now it has been unclear what kind of impact it had on flowering plants.
Plants do not have skeletons (骨骼) or exoskeletons like most animals, meaning fossils are relatively rare compared to animals, making it very difficult to understand the timeline of evolution from fossil evidence alone.
Dr. Jamie Thompson of the Milner Centre for Evolution and Dr. Santiago Ramírez-Barahona of Universidad Nacional Autónoma de México analyzed evolutionary "trees" constructed from changes in the DNA sequences (顺序) of up to 73,000 living species of flowering plants—angiosperms (被子植物). Using complex statistical methods, they fitted "birth-death" models to estimate the rates of extinction throughout geological time.
While the fossil record shows that many species did disappear, the ancestry to which they belong, such as families and orders, survived enough to flourish and then dominate. Evidence suggests that the vast majority of angiosperms families around today existed before the K-Pg event, of which some once shared Earth with the dinosaurs. Dr. Thompson said, "After most of Earth's species became extinct at K-Pg, angiosperms took the advantage, similar to the way in which mammals took over after the dinosaurs, and now pretty much all life on Earth depends on flowering plants ecologically."
So what made them tough enough to survive despite being immobile and relying on the sun for energy? Dr. Ramírez-Barahona said, "Flowering plants have a remarkable ability to adapt. They use a variety of seed-dispersal and pollination (授粉) mechanisms. Some have copied their entire genomes and others have evolved new ways to make use of solar energy."
