Intraspecific herbivory variability, rather than species' turnover, drives latitudinal patterns in community-wide herbivory

Abstract

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.