Understanding a warming world from ecological first principles
Thermal ecology and the Metabolic Theory of Ecology

Scaling-up respiration rates from individuals to populations & communities

The metabolic theory of ecology (MTE) makes reasonably accurate predictions about how biological rates change with temperature in individual organisms, however other ecological processes may modify these predictions when trying to predict the influence of temperature on processes occurring at higher scales of biological organization (i.e. population growth rates, total community photosynthesis or respiration). Lab members use a combination of theory, lab experiments, field experiments, and observational studies to “scale up” predictions of MTE. Some main focus area include:

• Understanding how density-dependent processes mediate individual-level responses to temperature
• Modelling how consumer-resource systems respond to warming
  
• The TEAMM experiment: Does MTE explain community and ecosystem responses to temperature in warmed metacommunites?

Nitrogen fixation with temperature

Nitrogen fixation is a highly conserved metabolic process that links ecosystem processes with nutrient availability, and it is known to be temperature dependent. We consider how nitrogen fixation may fit into MTE, and how a general thermal response of nitrogen fixation across biological scales may influence nitrogen cycling as the earth warms. We also use MTE and coexistence theory to model the interactive effects of temperature and nutrient availability on photosynthetic community structure and function.

Life history traits and body size change with warming

As temperature influences body size and metabolism, downstream biological traits and processes are constrained. Among these are various life history traits, including development rate, fecundity and fitness (Siegle et al JEMBE 2019, O’Connor et al 2007).

Along with temperature, body size is the greatest predictor of metabolic rates across the tree of life and body size is in turn strongly dependent on temperature. Our lab has formalized this feedback by incorporating the effects of temperature on body size into MTE models to better predict how temperature affects individuals and populations (Bernhardt et al. 2018).

Thermal ecology of host-parasite systems

Increasing temperatures and more variable thermal regimes are altering host – parasite dynamics around the globe. The complex nature of temperature – disease relationships has led to a call for general frameworks to help us better predict outcomes in often data-poor host – parasite systems, and the MTE provides one promising potential framework. Lab members use mathematical models of parasite spread, often tied together with models from the MTE, to try to understand how warming temperatures are likely to impact host – parasite systems and the resulting burden of infectious disease across biological systems.