Production efficiency differences among populations can be explained by physiology

Production efficiency may differ considerably among individuals and populations. Here we theoretically analyze to what extent differences in efficiency among populations relate to basic physiological processes. We derive characteristics for a stationary population of constant size using (1) an extended Bertalanffy growth equation and (2) Dynamic Energy Budget (DEB) theory to describe individual energetics and mortality combined with an additional thinning rule to provide a more realistic description of survival than the one usually made by only assuming constant background mortality. The production-assimilation ratio as predicted by DEB theory appeared to be strongly correlated with the Bertalanffy growth coefficient and the ultimate reproduction rate. Birds and to a lesser extent mammals have a much lower ratio than other taxa. Benthic marine invertebrate grazers, which are mainly molluscs, showed a higher ratio than pelagic grazers, mostly arthropods, which may have consequences for overall ecological efficiency when marine coastal systems get more dominated by the benthic compartment as a result of human impacts such as the construction of windfarms.