Dinosaur extinction changed plant evolution
Effects of missing large herbivores on food plants still detectable today
Date:
May 2, 2022
Source:
German Centre for Integrative Biodiversity Research (iDiv)
Halle-Jena- Leipzig
Summary:
The absence of large herbivores after the extinction of the
dinosaurs changed the evolution of plants. The 25 million years
of large herbivore absence slowed down the evolution of new plant
species. Defensive features such as spines regressed and fruit
sizes increased. The research has demonstrated this using palm
trees as a model system.
FULL STORY ==========================================================================
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 analysed 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." However, the defence traits of the plants;
spines and thorns on leaves and stems, showed a different picture:
the number of palm species with defence traits decreased during the megaherbivore gap. "Defence traits without predators apparently no
longer offered evolutionary advantages," says Onstein, who heads the
junior research group Evolution and Adaptation at iDiv. "However,
they returned in most palm species when new megaherbivores evolved,
in contrast to the changes in fruits, 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 affected plant evolution in the past can also
help predict future ecological developments. For example, the authors
have noted the loss of traits during the megaherbivore gap. 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 thus also affect trait variation
in plant communities and ecosystems today and in the foreseeable future.
========================================================================== Story Source: Materials provided by German_Centre_for_Integrative_Biodiversity_Research_
(iDiv)_Halle-Jena-Leipzig. Original written by Urs Moesenfechtel. Note:
Content may be edited for style and length.
========================================================================== Journal Reference:
1. Renske E. Onstein, W. Daniel Kissling, H. Peter Linder. The
megaherbivore
gap after the non-avian dinosaur extinctions modified trait
evolution and diversification of tropical palms. Proceedings of
the Royal Society B: Biological Sciences, 2022; 289 (1972) DOI:
10.1098/rspb.2021.2633 ==========================================================================
Link to news story:
https://www.sciencedaily.com/releases/2022/05/220502125356.htm
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