Rapidly rising temperatures will initiate numerous changes in plant-herbivore interactions as individual herbivores change their feeding behavior to match increasing metabolic demands. Higher metabolic rates, for example, should lead to higher herbivory rates as individuals attempt to maximize energy intake to fuel respiration and somatic growth. However, herbivore nutritional demands are more complex than energy alone. Nitrogen, for example, is 3 -5 times lower in plant foliage than in insect herbivore bodily tissues, such that insect herbivores experience consistent nitrogen limitation. Furthermore, nitrogen demand likely scales with temperature because proteins denature more rapidly at higher temperatures. Unfortunately, we know relatively little about the effects of temperature on potential nitrogen limitation of herbivore growth and feeding behavior. Here, I describe how temperatures induce physiological changes in herbivore nitrogen demand and the resulting impacts on plant-herbivore interactions.
Results/Conclusions
Rising temperatures alter the fundamental physiological processes of ectothermic herbivores. Herbivore metabolic rates increase exponentially with temperature, leading to greater consumption rates in order to fuel respiratory demands. Such increased consumption rates at high temperatures, however, reduce gut passage times and put herbivores at risk of lowering their nitrogen digestion efficiency. This reduced nitrogen digestion causes strong nitrogen limitation at high temperatures. As a result, warming increases herbivore performance but does so only on high nitrogen plants. These conclusions suggest that the effects of warming are a complex interaction of temperature, metabolic rates, nitrogen use efficiency, and plant nutritional quality. Herbivores might therefore focus feeding on a few poorly defended and nutritious plant species, altering plant community composition and ecosystem function in unexpected ways.