Ecological models predict that the effects of mammalian herbivore exclusion on plant diversity depend on resource availability and plant exposure to ungulate grazing over evolutionary time. Using an experiment replicated in 57 grasslands on six continents, with contrasting evolutionary history of grazing, we tested how resources (mean annual precipitation and soil nutrients) determine herbivore exclusion effects on plant diversity, richness and evenness. Here we show that at sites with a long history of ungulate grazing, herbivore exclusion reduced plant diversity by reducing both richness and evenness and the responses of richness and diversity to herbivore exclusion decreased with mean annual precipitation. At sites with a short history of grazing, the effects of herbivore exclusion were not related to precipitation but differed for native and exotic plant richness. Thus, plant species’ evolutionary history of grazing continues to shape the response of the world’s grasslands to changing mammalian herbivory.

生态模型预测哺乳动物食草动物排斥对植物多样性的影响取决于资源可用性和植物在进化时间内暴露于有蹄类动物的放牧。通过在六大洲的 57 个草原上重复进行的实验，对比放牧的进化历史，我们测试了资源（平均年降水量和土壤养分）如何决定食草动物排斥对植物多样性、丰富度和均匀度的影响。在这里，我们表明，在有蹄类动物放牧历史悠久的地点，食草动物排斥通过降低丰富度和均匀度来降低植物多样性，并且丰富度和多样性对食草动物排斥的反应随着年平均降水量而减少。在放牧历史较短的地方，食草动物排斥的影响与降水无关，但因本地和外来植物丰富度而异。因此，植物物种的放牧进化史继续影响着世界草原对不断变化的哺乳动物食草动物的反应。