Ecology as a science has lacked a general scientific theory capable of making predictions on ecological phenomena on various levels, but now a candidate for such a theory exists. This is termed the Metabolic Theory of Ecology (MTE) and states that energy use (metabolism) is a central process for all organisms that partly can be predicted from body size and then used to make predictions on ecological processes at the population and community level. However, there is some scepticism towards MTE as a general theory and so far the empirical support for it is mixed. In this project, different predictions of MTE will be studied to test the theory and see if and how it may need to be modified.
In this project we will (i) quantitatively assess the usefulness of MTE across several levels of biological organization and (2) develop MTE by analyzing how other factors and details of species biology can be included to increase its explanatory power. To begin with, we will study the relationship between growth and mortality in resource limited populations. Here, MTE predicts that in a population of growing individuals that uses the available resources to its limit, additional growth can only be achieved at the expense of mortality, along a so called selfthinning line. The slope of this line is determined by the metabolic rate of the organism and temperature. The accuracy of this prediction will be studied using laboratory experiments on various invertebrates (e.g. house cricket).
Second, using greenhouse experiments in combination with computer simulations we aim to study how well the outcome of species interactions can be predicted based on the body sizes of species and furthermore if the functioning and response of an entire ecological system can be predicted based on this. Third, using empirical data from various ecosystems we aim to study how well-known ecosystem patterns, such as the relationship between body size and abundance of species, and that between body size and trophic position in a food web, can be explained.
Taken together, this implies a critical and systematic assessment of the utility of MTE that will increase understanding of the factors that affect individual populations, how they interact with other populations and the patterns they give rise to in ecological systems. This knowledge is important to be able to make better predictions of how various environmental changes and perturbations on ecological communities may affect individual species as well as entire ecosystems.