The eco-evo-energetic framework. Energy available from the environment (influenced by biotic and abiotic conditions) is accumulated (A), assimilated (B) and used for expenditure on life history traits that influence fitness (C). Energetic limitation and genetic correlations result in trade-offs in expenditure among each life history trait (D), and optimal allocation results in enhanced fitness. Integrating fitness across all individuals in the population equals population growth (E) and population size in time step 1 is an important component of the biotic environment in time step t+1 (F).
Energy is arguably the most fundamental currency in biology. If an organism is unable to acquire sufficient energy from the environment to satisfy the basic necessities of life, it will be unable to survive or reproduce. Moreover, the energy that is acquired must be allocated among a number competing demands (e.g., growth, maintenance and reproduction). These tradeoffs form the basis of life history evolution theory and are well established on a theoretical level. There are real challenges in quantifying energetic status of free-ranging organisms, however, meaning that empirical tests of theory are rare. By collecting targeted measurements of energy acquisition (e.g., body composition) and expenditure (e.g., metabolic rate), we are attempting to expand upon recent accomplishments that have bridged both energetics and ecology (Brown et al. 2004. Toward a Metabolic Theory of Ecology. Ecology 85: 1771-1789) as well as ecology and evolution (e.g., Pelletier et al. 2009. Eco-evolutionary dynamics. Phil. Trans. Roy. Soc. B. 364: 1483-1489). Specifically, we are exploring the links across these three disciplines, in a proposed eco-evo-energetics framework. Current research questions include:
How does variation in energetic traits (e.g., ability to accumulate fat or food resources) influence life history variation (e.g., phenologies, reproductive success, survival)?
Does variation in energetic traits have evolutionary potential (i.e., is it heritable? genetically correlated with other traits?)?
How does selection act on variation in energetic traits?
What is the relevance of individual variation in energetic traits at a population level (i.e., in explaining variation in population demography and dynamics)?
Vaanholt, L.M., J.E. Lane, B. Garner and J.R. Speakman. 2016. Partitioning the variance in calorie restriction induced weight and fat loss in outbred mice. Obesity In Press.
Fletcher, Q.E., J.R. Speakman, S. Boutin, J.E. Lane, A.G. McAdam, J.C. Gorrell, D.W. Coltman and M.M. Humphries. 2014. Daily energy expenditure during lactation is strongly selected in a free-living mammal. Functional Ecology 29: 195-208.
Lane, J.E., S. Boutin, J.R. Speakman and M.M. Humphries. 2010. Energetic costs of reproduction to males in a scramble competition mating system. Journal of Animal Ecology 79: 27-34.