Eliminate the dinosaurs and let countless flowers bloom

When a mountain-sized mass of space rock collided with the Yucatán Peninsula 66 million years ago, the repercussions were horrific. Tsunami waves washed away coastlines, raging fires ravaged forests and dust and debris blocked out the sun for months. Nearly three-quarters of the planet’s species have been wiped out, most notably non-avian dinosaurs.

But one group seems to have weathered the storm. In an article published on Wednesday in the magazine Biology lettersResearchers provide evidence that flowering plants survived the Cretaceous-Paleogene, or K-Pg, mass extinction relatively unscathed compared to other organisms on Earth at that time. The disaster may have helped flowering plants flourish and become the dominant green things they are today.

“It is strange to think that flowering plants survived K-Pg while dinosaurs could not,” said Jamie Thompson, an evolutionary biologist at the University of Bath and one of the study’s authors.

Flowering plants are known to scientists as angiosperms. They originated in the Early Cretaceous, and were often overshadowed by older groups such as conifers and ferns. But they diversified rapidly as the mass extinction approached.

To determine how well flowering plants fared during the K-Pg extinction event, Dr. Thompson collaborated with Santiago Ramírez Barahona, an evolutionary geneticist at the National Autonomous University of Mexico. The couple’s work was initially hampered by a shortage of fossil flowers, which are rare compared to fossilized bones. Some of today’s largest angiosperm lineages, such as orchids, barely appear in the fossil record.

To uncover evolutionary insights missing from the fossil record, the researchers analyzed two evolutionary trees containing more than 100,000 living angiosperm species. These sprawling data sets, known as phylogenies, are calibrated using molecular clues that allow scientists to group related species together and determine when particular lineages diverged. Together, the lineages establish an evolutionary timeline for when the ancestors of modern angiosperm lineages appeared and when they became extinct.

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Researchers have discovered something surprising. While many species of angiosperms went extinct along with dinosaurs, pterosaurs, and marine reptiles—particularly those living near an asteroid’s impact crater—the larger lineages of flowering plants survived the extinction event and showed a relatively constant rate of extinction through time.

“I think this is actually a perfect fit with the plant fossil record,” said Paige Wilson Dibble, a paleontologist at the Burke Museum in Seattle who studies fossils from the K-Pg boundary in northeastern Montana and was not involved in the new study. “There is already a high rate of extinction at the species level, but all major lineages appear to have survived.”

This is in stark contrast to the evolutionary tree of dinosaurs. “Non-bird dinosaurs lost a lot of species, lost entire lineages, which we don’t see in angiosperms,” Dr. Thompson said.

While more work is needed to determine how angiosperms survived one of the deadliest extinctions in Earth’s history, researchers hypothesize that their ability to adapt played a role. Because flowering plants are pollinated by insects and wind, they have great reproductive flexibility. Their enormous diversity—by the end of the Cretaceous, grasses, sycamore trees, magnolias, and aquatic waterlilies had all appeared—may have also helped them survive devastation.

As Earth’s climate stabilized and life flourished, flowering plants took over terrestrial ecosystems. In 2021, researchers who compared Colombian fossils before and after the K-Pg boundary found that Extinction allowed angiosperms to dominate. This gave rise to the first rainforests, which remain hotbeds of diversity of flowering plants.

Dr Ramirez Barahona said this trend likely occurred in ancient ecosystems around the world. “Before and after the impact of K-Pg, the entire environmental composition changed,” he said. “They have restructured themselves into these new flowering ecosystems.” Today, approximately 80 percent of all land plants are angiosperms.

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In this way, the impact that wiped out the dinosaurs led to the emergence of modern ecosystems. Instead of giant reptiles, these habitats were inhabited by mammals, which persisted through the mass extinction alongside flowering plants, and were poised for a similar explosion in diversity.

After the K-Pg boundary, “we started to see plants and animals that we could recognize,” Dr. Wilson Dibble said. “In this truly dynamic time of giant ecological catastrophes and mass extinctions, the environment becomes similar to what we see today.”

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