(ORDO NEWS) — After the extinction of the large flightless dinosaurs 66 million years ago, large herbivores were absent from Earth for the next 25 million years.
Since plants and herbivores influence each other, the question arises whether this very long absence and subsequent return of the so-called “megaherbivores” influenced the evolution of the plant world.
To answer this question, a research team led by iDiv and the University of Leipzig analyzed fossil and living palm trees. Genetic analysis allowed researchers to trace the evolutionary development of plants during and after the absence of megapredators.
So, for the first time, they confirmed the widespread scientific assumption that many types of palm trees in the time of dinosaurs bore large fruits and were covered with thorns and thorns on trunks and leaves.
However, the team of researchers found that the “evolutionary rate” at which new palm species with small fruits emerged during the megaherbarium decreased, while the rate of evolution of species with large fruits remained almost unchanged.
The size of the fruits themselves, however, also increased. Thus, palm trees with large fruits existed even after the extinction of the dinosaurs. Apparently, much smaller animals could also eat the large fruits and spread the seeds with their secretions.
“In this way, we were able to disprove the previous scientific assumption that the presence of large palm fruits depended solely on mega-herbivores,” said the first author of the study, Dr. Renske Ohnstein from iDiv and the University of Leipzig. “Therefore, we assume
However, plant defenses thorns and spines on leaves and stems showed a different picture: the number of palm species with defense traits has declined during the absence of megaherbivores.
“Defensive traits without predators obviously no longer conferred evolutionary advantages,” says Onstein, who leads the Evolution and Adaptation Junior Research Group at iDiv. “However, they returned in most palm species when new mega herbivores appeared, in contrast to the changes in the fruit that persisted.”
With their work, the researchers shed new light on evolution and adaptation in one of the most mysterious and unique periods in the history of plant evolution – during and after the extinction of megaherbivores.
Understanding how the extinction of megaherbivores affected plant evolution in the past could also help predict future environmental events. For example, the authors note the loss of characters during the extinction of megagerbivores.
This loss can affect important ecosystem functions and processes such as seed dispersal or herbivory. Thus, the continued extinction of large animals due to human hunting and climate change may also affect trait variation in plant communities and ecosystems today and for the foreseeable future.
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