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Phys.org has a story about plant evolution after the K-Pg mass extinction. Mass extinction always have irreversible effects on the evolution of life on Earth. The end Cretaceous extinction took out about 75% of species, including non-avian dinosaurs, pterosaurs, ammonites, and other countless others. The Plant Kingdom isn't always discussed, but it suffered heavy losses, too. New research in the Proceedings of the Royal Society B looks not at the extinction of plants, but at the effects of the missing megaherbavores on the evolution of plants.
With the extinction of large, non-flying dinosaurs 66 million years ago, large herbivores were missing on Earth for the subsequent 25 million years. Since plants and herbivorous animals influence each other, the question arises whether, and how this very long absence and the later return of the so-called "megaherbivores" affected the evolution of the plant world.
To answer this question, a research team led by iDiv and Leipzig University analyzed fossil and living palms today. Genetic analyses enabled the researchers to trace the evolutionary developments of plants during and after the absence of megaherbivores. Thus, they first confirmed the common scientific assumption that many palm species at the time of the dinosaurs bore large fruits and were covered with spines and thorns on their trunks and leaves.
However, the research team found that the "evolutionary speed" with which new palm species with small fruits arose during the megaherbivore gap decreased, whereas the evolutionary speed of those with large fruits remained almost constant. The size of the fruits themselves, however, also increased. So, there were palms with large fruits even after the extinction of the dinosaurs. Apparently, much smaller animals could also eat large fruits and spread the seeds with their excretions. "We were thus able to refute the previous scientific assumption that the presence of large palm fruits depended exclusively on megaherbivores," says the study's first author Dr. Renske Onstein from iDiv and Leipzig University. "We therefore assume that the lack of influence of large herbivores led to denser vegetations in which plants with larger seeds and fruits had an evolutionary advantage."
