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This chapter considers a concept of niche that emphasizes multidimensional spaces of scenopoetic variables and provides a natural connection to the study of geographic distributions of species. It first explains the relations between environmental and geographic spaces before discussing the use of equations to link spatially explicit population growth patterns to variation in the ecological characteristics of species. It then describes the BAM diagram, a Venn diagram that displays the joint fulfillment in geographic space of three sets of conditions that together determine species distribution: biotic conditions, abiotic conditions, and movement of the species. The chapter also explores the spatial resolution of scenopoetic variables, estimation of the fundamental and existing fundamental niches, the biotically reduced niche, and caveats about reducing Grinnellian niches and the Eltonian Noise Hypothesis. Finally, it shows how distributional areas and ecological niches can be estimated.

This chapter explores the conceptual bases for the discrepancy between species’ potential geographic distributional areas and their occupied distributional areas, focusing on the case of conditions when the Eltonian Noise Hypothesis is true as well as the necessary modifications when it is not. It first considers the meaning of the potential distributional area and the reasons why an ecological niche model may not estimate it correctly. It then explains why a species may not be at equilibrium with its potential distributional area, but rather inhabits only some subset of areas suitable for it. It also discusses nonequilibrium distributions that may arise in terms of the BAM diagram before concluding with an analysis of procedures for further processing of a niche model, which expresses potential geographic distributional area, to yield an estimate of occupied distributional area.

This book has described a comprehensive framework for thinking about the geography and ecology of species distributions, arguing that such a framework is critical to further progress in the field of ecological niches and distributions. To develop this framework, traditional concepts in ecology have been radically reworked. In this conclusion, some of the challenges for future work regarding ecological niche modeling are discussed, such as fully integrating the BAM diagram with central concepts of population biology and statistical theory; clarifying the notion of niche conservatism versus niche evolution as regards scenopoetic versus bionomic environmental dimensions; and improving the link between correlational and mechanistic approaches to estimating and understanding ecological niches. The book argues that careful conceptual thinking must be combined with detailed empirical exploration in order to address each of these challenges.