Multiple dimensions of biodiversity mediate effects of temperature on invertebrate herbivory in a montane grassland

Abstract

Invertebrate herbivores are important and diverse, and their abundance and impacts will likely shift under climate change. Yet, past studies of invertebrate herbivory have documented highly variable responses to changing temperature, making it challenging to predict the direction and magnitude of these shifts. One explanation for these responses is that changing environmental conditions drive concurrent changes in plant communities and herbivore traits. The impacts of changing temperature on herbivory might therefore depend on how temperature combines and interacts with characteristics of plant and herbivore communities. To test this, we surveyed damage to leaves by invertebrate herbivores on 4400 plant individuals in 220 sampling plots along a 1101 m elevational gradient. Increasing temperature drove community‐level herbivory via at least three overlapping mechanisms: increasing temperature directly reduced herbivory, indirectly affected herbivory by reducing plant‐community phylogenetic diversity, and indirectly affected herbivory by altering the effects of plant‐community functional and phylogenetic diversity on herbivory. Consequently, increasing plant functional diversity reduced herbivory in colder environments while increasing plant phylogenetic diversity increased herbivory in warmer environments. Moreover, different herbivore feeding guilds varied in their response to temperature and plant community composition. These results indicate that, even along a single elevation gradient in a single year, a variety of mechanisms can concurrently drive herbivory, thereby supporting the hypothesis that a universal response of herbivory to changing environmental conditions is unlikely to exist. Instead, our results highlight the importance of considering both plant and herbivore community context to predict how climate change will alter invertebrate herbivory.