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

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-meter 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.