The effects of missing large herbivores on food plants are still detectable today


With the extinction of the large non-flying dinosaurs 66 million years ago, large herbivores became extinct on Earth for the next 25 million years. Since herbivorous plants and animals influence each other, the question arises whether and how this very long absence and the subsequent return of the so-called “megaherbivores” affected the evolution of the plant world.

To answer this question, a research team led by iDiv and the University of Leipzig today analyzed fossil and living palms. Genetic analyzes have allowed 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 species of palm trees during the dinosaur era bore large fruits and were covered with thorns and thorns on their trunks and leaves.

However, the research team found that the “evolutionary speed” with which new species of small-fruited palms emerged during the megaherbivorous gap has decreased, while the evolutionary speed of large-fruited ones is remained almost constant. However, the size of the fruits themselves also increased. Thus, there were large-fruited palms even after the extinction of the dinosaurs. Apparently much smaller animals could also eat large fruits and spread the seeds with their excreta. “We were thus able to refute the previous scientific hypothesis that the presence of large palm fruits depended exclusively on megaherbivores,” says the first author of the study, Dr. Renske Onstein from iDiv and the University of Leipzig. . “We therefore hypothesize that the lack of influence from large herbivores led to denser vegetations in which plants with larger seeds and fruits had an evolutionary advantage.”

However, plant defense traits; thorns and thorns on leaves and stems, showed a different picture: the number of palm species with defensive traits declined during the megaherbivorous breach. “Predatorless defense traits apparently no longer offered evolutionary advantages,” says Onstein, who leads the Evolution and Adaptation junior research group at iDiv. “However, they returned to most palm species when new megaherbivores evolved, unlike changes in fruit, which persisted.”

With their work, the researchers shed new light on evolution and adaptation during one of the most enigmatic and unique periods in the history of plant evolution, during and after megaherbivore extinctions. . Understanding how megaherbivore extinctions have affected plant evolution in the past can also help predict future ecological developments. For example, the authors noted the loss of traits during megaherbivore straying. This loss can affect important ecosystem functions and processes, such as seed dispersal or herbivory. The ongoing extinction of large animals due to human hunting and climate change may therefore also affect trait variation in plant communities and ecosystems now and in the foreseeable future.

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Material provided by German Center for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig. Original written by Urs Moesenfechtel. Note: Content may be edited for style and length.


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