Predicting Indirect Effects of Predator-Prey Interactions

Predicting the effects of climate change on species and communities remains a pre-eminent challenge for biologists. Critical among this is understanding the indirect effects of climate change, which arise when the direct, physiological effects of climate on one species change the outcome of its interaction with a second species, altering the success of the second species. A diverse array of approaches to predicting indirect effects exists from mechanistic models, which attempt to build-up from physiological changes to ecological consequences, to ecological models that focus solely on the ecological scale. Here I review studies of the indirect effects of temperature on two predator-prey systems in rocky intertidal habitats. Laboratory and field studies have shown that temperature can indirectly affect interactions through both physiological and behavioral changes in predator and prey, but no model yet captures the full range of these effects. The three main categories of changes are metabolic rate effects, stress effects, and behavioral avoidance. Mechanistic models best capture the first two of these three dynamics, while ecological models have focused mainly on the last two. The challenge remains to correctly identify a species' vulnerability to climate change, which differs from its physiological sensitivity. The best approach may be to use detailed physiological-scale studies of indirect effect in a few systems to ground truth simpler models that can be applied more broadly. Model development and testing is also hampered by the small number of field studies of indirect effects in natural systems, particularly studies that examine natural temporal or spatial variation in climate.