Direct effects of elevated temperature on a tri-trophic system: Salix, leaf beetles and predatory bugs

The net effect of climatic change on biotic interactions will depend on how each interacting species is individually affected. Elevated temperatures are predicted to have differential effects on species across trophic levels, due to asymmetric sensitivity to temperature changes. In this study, we examined the direct effects of three temperature regimes (16, 20 and 24 A degrees C) that reflect present and, potentially, future climate conditions on the response of Salix spp. plants, an important bioenergy crop, and its most damaging herbivore (Phratora vulgatissima) and an efficient natural enemy (the omnivorous predator Orthotylus marginalis). We found that plant growth, herbivore oviposition and enemy egg-foraging rate correlated positively with temperature. In the event of elevated temperatures following global climatic changes, these species could potentially respond in tandem. Still, the strength of responses varied among species, with herbivore and natural enemy exhibiting a similar and steeper rate of response relative to plants. Additionally, the herbivore's response was influenced by plant quality with altered oviposition rates depending on whether it was fed the (previously determined) resistant Salix dasyclados or susceptible S. viminalis. This indicates that host plant chemistry has the potential to mediate differential responses to temperature. Together, our results suggest that indirect effects of elevated temperatures, leading to a disruption of trophic associations, may be less likely or less severe in this tri-trophic system.