Geographical variation in community-wide herbivory matches patterns of intraspecific variation instead of species turnover

We selected 43 grassland sites along a 1,500-km latitudinal gradient (c. 27°N to 39°N) and a 2,698-m elevational gradient (1,886 m to 4,584 m) on the Qinghai-Tibetan Plateau. We calculated the overall herbivory percentage (ranging from 0% to 100%) for each plant species by first multiplying the number of leaves in each damage class by the median removal value for that class (i.e., 0%, 2.5%, 7.5%, 15.0%, 35.0%, or 75.0%). Obtained values were then summed across all damage classes and the sum divided by the total number of leaves (including undamaged ones) in a sample. We calculated community-weighted mean of herbivory (hereafter, ‘CWM herbivory’) as the measurement of community-wide herbivory, which is calculated as summed species’ (herbivory) means weighted by their abundance. We evaluated geographical patterns in invertebrate herbivory pressure at the population- and community-levels, while also evaluating the importance of geographical variation in mediating the effects of abiotic and biotic factors on intraspecific variation (through changes in herbivory on component species) and species turnover effects (through changes in plant community composition).