Climate change is affecting both geographic ranges and interspecific interactions. Range limit theory predicts that climatic effects on ranges limits will depend on both abiotic stress and biotic interactions. We examined the effects of experimental watering and warming on leaf water content and herbivory rates on a native perennial plant, pacific silverweed (Argentina anserina ssp. pacifica), across a gradient of precipitation in coastal California.
Results/Conclusions
We found that watering increased leaf water content at both wetter and drier sites, but only increased herbivory in drier conditions. Warming increased herbivory irrespective of local climate. Range limit theory (species interaction-abiotic stress hypothesis) predicts that the impacts of abiotic stress and biotic interactions trade off across stress gradients, with abiotic stress being more influential at the drier edge of the range. Our results were consistent with this expectation. Given predictions that the study locales will become warmer and drier with climate change, our results suggest that the effects of warming and drying on herbivory may counteract each other in drier regions of the range of Argentina anserina, while in wetter regions warming may increase herbivory without a corresponding decline due to drying.