UC Santa Barbara

Temperature constrains the rates of ecological processes that drive community- and ecosystem-level patterns by dictating the energetic demands of individual organisms. The Metabolic Theory of Ecology (MTE) predicts that increases in temperature drive proportional increases in the standard metabolic rates (SMR) and predation rates of consumers, offering a framework for linking temperature-dependent physiological processes to predator-prey dynamics. However, while many taxa do exhibit increases in predation at higher temperatures, the strength of this relationship often deviates from MTE predictions. One reason for this may be that MTE does not consider a number of key features of metabolism, such as maximum metabolic rate (MMR) and aerobic scope (AS), that are important determinants of energetic demands and resultant behaviors. Here, we quantify how changes in temperature alter the metabolism (SMR, MMR, AS) and predation rates of an important marine predator, the California spiny lobster (Panulirus interruptus), to describe how temperature alters the functional role of lobsters. We show that temperature extremes within the species’ current thermal range impose physiological constraints that would be otherwise undetectable using the MTE framework alone. For example, a regional low of 11°C reduced standard metabolic rate and aerobic scope by 70 and 38%, respectively, as compared to a regional high of 21°C, resulting in near cessation of predation. On the contrary, an extreme thermal high of 26°C permits sustained predation to fuel elevated metabolic demands, however reductions in factorial aerobic scope may necessitate long-term fitness tradeoffs. While theoretical scaling relationships that predict proportional increases in metabolism and predation with rising temperature can provide a foundational null hypothesis for the effects of climate change on population and community dynamics, they ignore the variety of ways in which temperature can influence physiological performance to alter ecological responses.