Flowering plants survived the asteroid that killed the dinosaurs, and may outlive us

Flowering plants survived the asteroid that killed the dinosaurs, and may outlive us

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If you had looked up 66 million years ago, you might have seen, for a split second, a bright light like a mountain-sized asteroid burning through the atmosphere and crashing into Earth. It was springtime and the actual end of the Mesozoic Era.

If you somehow survived the initial impact, you would have witnessed the devastation that followed. Raging firestorms, massive tsunamis, and nuclear winters that last from months to years. The 180-million-year reign of the non-avian dinosaurs ended in the blink of an eye, as did at least 75% of the species that shared the planet with them.

In the wake of this event, known as the Cretaceous-Paleogene (K-Pg) mass extinction, a new dawn came for Earth. The ecosystems had revived again, but the life that inhabited them was different.

Many famous pre-K-Pg types can only be seen in the museum. The enormous Tyrannosaurus rex, Velociraptor, and winged dragons of the genus Quetzalcoatlus could not survive the asteroid, and are trapped in deep history. But if you take a walk outside and smell the roses, you will be in the presence of ancient lineages that flourished in the ashes of K-Pg.

Although the living species of roses are not the same species that shared Earth with Tyrannosaurus rex, their lineage (family Rosaceae) originated tens of millions of years before the asteroid hit.

Roses are not an unusual breed of angiosperms (flowering plants) in this regard. Fossils and genetic analysis indicate that the vast majority of angiosperm families arose before the asteroid.

The ancestors of the ornamental orchid families, the magnolia and passionflower families, the grass and potato families, the medicinal daisy family, and the herbaceous mint family, all shared the land with dinosaurs. In fact, the massive evolution of angiosperms to approximately 290,000 species today may have been facilitated by K-Pg.

Angiosperms seem to have benefited from a fresh start, similar to the first members of our lineage, the mammals.

However, it is not clear how they did this. Angiosperms, which are extremely fragile compared to dinosaurs, cannot fly or run to escape harsh conditions. They depend on sunlight for their existence, which has been erased.

What do we know?

Excavations in different areas tell different accounts of events. There was clearly a rise in angiosperm turnover (loss and reemergence of species) in the Amazon when the asteroid hit, and a decline in plant-eating insects in North America, suggesting a loss of food plants. But other regions, such as Patagonia, show no pattern.

A 2015 study analyzing fossil angiosperms from 257 genera (families typically contain multiple genera) found that K-Pg had little effect on extinction rates. But it is difficult to generalize this result to 13,000 angiosperm genera.

My colleague Santiago Ramírez Barahona, from the National Autonomous University of Mexico, and I took a new approach to resolve this confusion in a study we published in Biology letters. We analyzed large angiosperm family trees, which previous work had drawn through mutations in the DNA sequences of 33,000 to 73,000 species.

Magazine information:
Biology letters

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