Eltonian shortfall due to the Grinnellian view: functional ecology between the mismatch of niche concepts

A number of recognized shortfalls currently exist in biology. They are related to 1) a disparity between the species described and the actual number of species; 2) uncertainties in species’ geographical distribution; 3) scarcity of species abundance data and 4) a lack of evolutionary data. Here, we discuss how attempts to solve the Eltonian shortfall (scarcity of knowledge about intra‐ and interspecific interactions, responses of species to environment and the effects of species on ecosystems) based on functional ecology must be aware of the pitfalls of using a Grinnellian view (broad scale) to address local questions (Eltonian scale). Since the characterization of species’ requirements and their effects on the environment (Eltonian niche) is based on functional traits, it is important to recognize that the Grinnellian niche is focused on the requirements but not the effect of species on a given habitat. By neglecting the dichotomy between the Eltonian and Grinnellian niches, choosing traits based on large‐scale datasets to address local questions to describe the niche of a species may lead to two pitfalls. The first applies to situations where traits that may predict potential distribution and coexistence at large scales (Grinnellian view) are often not suitable for explaining coexistence at local scales (Eltonian view). Since the Eltonian niche comprises the requirements and impacts of species at a local scale, the second pitfall is that the selection of traits only based on their significance at coarse scales may ignore the distinction between response and effect traits. We present a theoretical framework that explores the Eltonian shortfall, and discuss possible solutions. We provide a conceptual basis to aid in the choice of traits with respect to niche concepts and population ecology for dealing with the Eltonian shortfall.