Summary Plant pathogens and their hosts often coexist with mammal grazers. However, the direction and strength of grazing effects on foliar fungal diseases can be idiosyncratic, varying among host plant species and pathogen types. We combined a 6 yr yak‐grazing experiment, a clipping experiment simulating different mammal consumption patterns (leaf damage vs whole‐leaf removal), and a meta‐analysis of 63 comparisons to evaluate how grazing impacts foliar fungal diseases across plant growth types (grass vs forb) and pathogen life histories (biotroph vs necrotroph). In the yak‐grazing experiment, grazing had no significant effect on disease severity, and grasses experienced a higher disease severity than forbs; there was a significant interaction between pathogen type and grazing. In both the yak‐grazing experiment and meta‐analysis, grazing decreased biotrophic pathogens (mainly rusts and powdery mildew), but did not affect necrotrophic pathogens (mainly leaf spots). The clipping experiment suggested that grazers might promote infection by necrotrophic pathogens by producing wounds on leaves, but inhibit biotrophic pathogens via leaf removal. In conclusion, our three‐part approach revealed that intrinsic properties of both plants and pathogens shape patterns of disease in natural ecosystems, greatly improving our ability to predict disease severity under mammal grazing.

The rapid biodiversity losses of the Anthropocene have motivated ecologists to understand how biodiversity affects infectious diseases. Spatial scale is thought to moderate negative biodiversity-disease relationships (i.e., dilution effects) in zoonotic diseases, whereas evidence from plant communities for an effect of scale remains limited, especially at local scales where the mechanisms (e.g., encounter reduction) underlying dilution effects actually work.Here, we tested how spatial scale affects the direction and magnitude of biodiversity-disease relationships. We utilized a 10-year-old nitrogen addition experiment in a Tibetan alpine meadow, with 0, 5, 10, and 15 g/m 2 nitrogen addition treatments. Within the treatment plots, we arranged a total of 216 quadrats (of either 0.125 Â 0.125 m, 0.25 Â 0.25 m or 0.5 Â 0.5 m size) to

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Aim: Attempts over the past 30 years to explain geographical variation in the strength of herbivore pressure have given rise to ecological hypotheses like the latitudinal herbivory hypothesis. This hypothesis, however, has rarely been tested using communitylevel data. Therefore, the aim of our study was to examine the patterns and potential mechanisms underlying geographical variation in community-wide herbivory. Location:The Qinghai-Tibetan Plateau. Time Period: July 2021.Major Taxa Studied: Plants. Methods:We selected 43 grassland sites along a 1500-km latitudinal gradient (c. 27°N to 39°N) and a 2698-m elevational gradient (1886-4584 m) on the Qinghai-Tibetan Plateau. 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).Results: Community-wide herbivory decreased with latitude, mirroring intraspecific variation, while species turnover effects did not vary along any tested geographical gradients. Furthermore, we found that geographical variation in community-wide herbivory was strongly positively correlated with soil nitrogen content. We also found a positive effect of soil nitrogen content on intraspecific variation and a negative effect of plant community biomass on species turnover effects. Main Conclusions:The latitudinal gradient in community-wide herbivory was primarily mediated by intraspecific variation, which was in turn associated with a gradient in soil nitrogen content. Our findings highlight the need for community-wide assessments of geographical variation in plant-herbivore interactions, decomposing community-wide herbivory into intraspecific variation and species turnover effects.

Attempts over the past 30 years to explain geographic variation in the strength of herbivore pressure gave rise to the latitudinal herbivory hypothesis. However, this long-standing hypothesis has rarely been tested using community-level data. In this study, we selected 43 grassland sites along a 1,500-km latitudinal gradient (c. 27°N to 39°N) on the Qinghai-Tibetan Plateau. We calculated community-wide herbivory at each site by summing herbivory across plant species weighted by the biomass of each species; we then investigated how abiotic and biotic latitudinal correlates drove community-wide herbivory via their effects on intraspecific herbivory variability and species’ turnover. We found that community-wide herbivory decreased with latitude, mirroring intraspecific herbivory variability. Furthermore, intraspecific herbivory variability was driven by climatic factors, but not edaphic or plant community factors. Overall, our study highlights the importance of considering both intraspecific herbivory variability and species’ turnover for predicting how climate change will alter community-wide herbivory.