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   PID: hpt/lnx 1.9.0-cur 2019-01-08   
   TID: hpt/lnx 1.9.0-cur 2019-01-08   
    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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