Sideoats grama (Bouteloua curtipendula var. caespitosa) plants, grown from plant communities with similar composition that did or did not have a long history of cattle grazing, were defoliated every 14, 28, or 56 days to determine whether previous exposure to grazing affected plant response to herbivory. Plants grown from populations that had been previously exposed to grazing had lower mortality than plants grown from ungrazed populations, indicating that grazing history influenced plant herbivory tolerance. Plant height and leaf growth angle were not as responsive to clipping treatments in plants that were grown from previously grazed populations, indicating that resistance mechanisms were present in the previously grazed plants before clipping treatments were applied. These results suggest that plant populations can develop grazing tolerance and resistance mechanisms when exposed to a long history of grazing, however, the author cautions that plants populations with these specific mechanisms may have lower genetic variability and will be less adaptive to other disturbances than plant populations without them.
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