Body size, in conjunction with diet, has been used extensively as a simple characterization of the ecological niche of species and to investigate the evolutionary and ecological assembly of communities.  However, body size can be considered a proxy for a more fundamental driver: individual energy use. Energy is a core ecological currency and modeling its fluxes has helped address basic questions of species - environment interactions and ecosystem processes.  A perspective that combines these two viewpoints is to consider the energetic position or “energetic niche” of a species. It can be quantified as species’ primary productivity required (PPR), i.e. the amount of energy from primary productivity needed to sustain the daily energy needs of an individual.  PPR integrates information on body size, diet, and trophic transfer inefficiencies into one single measure.
We assess how energetic niches may dictate the abundance structure of species within a taxonomically-defined community. Using a simple model, PPR distributions are used to predict abundances of all species as well as taxonomic and ecological aggregations (orders, feeding guilds) in a community and compare them with observed abundances.
We complement these analyses with an extensive population-level assessment of PPR as a predictor of inter and intra-specific abundance patterns in mammals.
Results/Conclusions

Across communities, predicted rank-abundance distributions (RADs) are very similar to empirical RADs. Congruence between PPR-predicted and observed abundances is seen at the feeding guild and order levels within each community with weaker fits at the species level.  PPR is also a good predictor of mammalian abundances for a globally dispersed dataset and offers consistently stronger prediction than body size as a standalone predictor.
In summary, we find that the simple energetic models presented offer a sound first-order prediction of observed animal abundances at population and community levels. These findings underpin the importance of the energetic niche of species in studies of abundance and suggest several applications for the presented energetic framework in population and community ecology and conservation.