A Hierarchical Framework to Assess Ecological Niche Across Levels of Biological Organization

ABSTRACT Background Ecological niches are commonly treated as species‐level properties, assuming uniform responses to environmental and biotic gradients. However, empirical evidence increasingly shows that ecological differentiation often arises within species, as populations experience distinct environmental regimes, biotic interactions and evolutionary histories. These patterns highlight the need for a framework that captures how niche attributes emerge across levels of biological organization. Conceptual Framework We develop a hierarchical framework for the Hutchinsonian niche in which ecological structure becomes most coherent at the population level, where local selection, demography and ecological interactions intersect. Within this framework, niche attributes such as position, breadth and functional organization arise from population‐level processes and integrate non‐additively into species‐level niche envelopes, while remaining fully compatible with classical theory. Empirical Synthesis Evidence from diverse taxa and ecosystems demonstrates consistent divergence among populations in climatic tolerances, resource use and functional traits. These divergences reflect localized ecological filtering, dispersal constraints and adaptive differentiation, and are supported by genetic, isotopic and trait‐based studies. Together, these findings indicate that population‐level structure is a pervasive component of ecological niches. Implications A hierarchical niche framework improves the mechanistic basis for ecological modelling, biogeographic inference and conservation. Extending the classical Biotic–Abiotic–Mobility (BAM) framework to its population‐structured formulation (BAMp) enables characterization of population‐specific abiotic, biotic and mobility components. We outline operational approaches—including spatial stratification, hierarchical modelling and integration of functional and movement data—to incorporate population‐level structure into ecological analyses. Conclusion By making explicit the hierarchical organization through which ecological structure emerges, this framework provides a more biologically grounded basis for interpreting ecological niches and species' environmental responses under environmental change, and enables the identification of ecologically meaningful units for conservation.