Spatial Scale and Biodiversity

by

Daniel J. McGlinn, Michael W. Palmer

• LAST REVIEWED: 19 October 2022
• LAST MODIFIED: 27 February 2019
• DOI: 10.1093/obo/9780199830060-0210

Introduction

The scale of observation leaves an indelible mark on our understanding of biodiversity. Despite wide recognition among ecologists that scale is important, most theories of biodiversity and coexistence treat mechanisms as scale-independent (e.g., coexistence theory). Furthermore, most empirical tests of theory are still only performed at a single spatial scale. A fuller understanding of scale is likely to help resolve some of ecology’s ongoing controversies. Does biodiversity increase productivity? Is the world experiencing the sixth major mass extinction? Are species interactions relevant to understanding biodiversity? Does exotic biodiversity decrease native biodiversity? We know the answers to these questions depend in large part on scale. However simply recognizing that scale plays a role is not sufficient, and currently several bodies of theory are emerging that provide a vision of a more unified ecology in which scale plays a central role. Ultimately, the daunting problems facing biodiversity require that we consider scale directly in our hypotheses. The goal of this bibliography is to highlight key papers that define scale and discuss how it influences biodiversity patterns. Another Oxford Bibliographies in Ecology article, “Species-Area Relationships” by Samantha M. Tessel, Kyle A. Palmquist, and Robert K. Peet is devoted entirely to the species-area relationship and therefore that topic is covered in less depth here.

General Overviews

The recognition of the importance of scale to biodiversity emerged in the first part of the 20th century in literature on the species-area relationship and island biogeography (see also under Oxford Bibliographies in Ecology “Island Biogeography Theory” by Gonçalo Ferraz). It was not until the late 1980s that work on scale began to flourish and in the 1990s that the ideas were reviewed in a comprehensive way. Ricklefs and Schluter 1993 provided an edited collection of papers that showed how scale was first starting to be incorporated into local community ecology to allow for links with biogeography. Rosenzweig 1995 demonstrated the insights that can be gained by applying equilibrium theory across spatial and temporal scales. Brown 1995 christened the new field of macroecology by synthesizing work on the intersection of energetics, body size, and community assembly to provide a new framework for addressing patterns of biodiversity. Hubbell 2001, in contrast to Rosenzweig 1995 and Brown 1995, removed the emphasis on interspecific demographic differences and environmental filtering as necessary explanations for biodiversity patterns. Instead, Hubbell 2001 emphasized the previously neglected roles of dispersal limitation, ecological drift, and stochastic speciation on biodiversity patterns. Storch, et al. 2007 provided an edited synthesis of perspectives on biodiversity that emphasized both stochastic (as in Hubbell 2001) and deterministic explanations for patterns such as the species-area relationship and latitudinal diversity gradient. McGill 2010 unified many of the models presented in Storch, et al. 2007 by demonstrating why very different models can result in similar biodiversity patterns. Harte 2011 provided a unique neutral explanation of biodiversity patterns that does not evoke any mechanisms (at least as they are traditionally thought of by ecologists) and instead provides predictions about community structure that are derived under the assumption that communities are arranged in a most likely state. Vellend 2016 synthesized the stochastic and deterministic views of ecology by unifying various models and hypotheses using just four key processes—selection, dispersal, drift, and speciation—which represents a generalization of the approach taken in population genetics. Leibold and Chase 2017 embraced and broadened the vision in Vellend 2016 of unifying ecology under these four mechanisms and suggested more directly how scale should play a central role in developing and testing the metacommunity concept of biodiversity that explicitly recognizes the spatial and temporal arrangement of species’ underlying biodiversity patterns.

• Brown, J. H. 1995. Macroecology. Chicago: Univ. of Chicago Press.

  Brown provides a vision for a new field of ecology that searches for general patterns across habitats and taxonomic groups. He suggests that if one wishes to predict the dynamics of a system it is not sufficient to understand the parts of the system; rather it is important to also study the system as a whole. Brown uses this approach to examine patterns of species distribution and community assembly at local to continental scales.

• Harte, J. 2011. Maximum entropy and ecology: A theory of abundance, distribution, and energetics. New York: Oxford Univ. Press.

  DOI: 10.1093/acprof:oso/9780199593415.001.0001

  The book develops the maximum entropy theory of ecology (METE) which is a neutral model for spatial patterns of biodiversity that assumes that communities are arranged in a most likely state given measured constraints. METE represents a null hypothesis about biodiversity patterns that evokes no explicit ecological or evolutionary mechanisms. This book also provides an overview of biodiversity concepts with a focus on spatial and body-size distributions of communities.

• Hubbell, S. P. 2001. The unified neutral theory of biodiversity and biogeography. Princeton, NJ: Princeton Univ. Press.

  This book builds off the theory of island biogeography and proposes that biodiversity patterns such as the species-abundance distribution, species-area relationship, and distance decay of similarity were not due to species differences but rather to stochastic processes such as dispersal, ecological drift, and chance speciation. Hubbell demonstrates how a continental-scale process such as speciation can influence local biodiversity patterns.

• Leibold, M. A., and J. M. Chase. 2017. Metacommunity ecology. Princeton, NJ: Princeton Univ. Press.

  DOI: 10.2307/j.ctt1wf4d24

  This book has an even broader goal than Vellend 2016 and extends the focus to how the processes influence the spatial and temporal patchiness of metacommunities. The authors discern how different models of community assembly may be contrasted in a useful way.

• McGill, B. J. 2010. Towards a unification of unified theories of biodiversity. Ecology Letters 13.5: 627–642.

  DOI: 10.1111/j.1461-0248.2010.01449.x

  McGill unifies the many different unified theories of biodiversity (several of which are described in Storch, et al. 2007) as special cases of a more general framework that relies on three premises: 1) most species are rare, 2) species are independent, 3) individuals within species are aggregated. If these three criteria are met, then McGill argues that regardless of the processes that the model evokes it will generate broadly similar macroecological patterns to what we observe in nature. Available online.

• Ricklefs, R. E., and D. Schluter, eds. 1993. Species diversity in ecological communities. Chicago and London: Univ. of Chicago Press.

  An edited collection of papers around the theme of biodiversity and biogeography that attempts to unify the importance of the effects of historical and contemporary processes on the generation and maintenance of biodiversity. This collection was one of the first syntheses that recognized the connection and importance of both spatial and temporal scale on the processes shaping biodiversity patterns.

• Rosenzweig, M. L. 1995. Species diversity in space and time. Cambridge, UK: Cambridge Univ. Press.

  DOI: 10.1017/CBO9780511623387

  This book examines both spatial and temporal patterns from local-to-global and paleo-to-modern across a range of taxonomic groups focusing on plants and animals. Rosenzweig uses the species-area relationship to reveal how sampling effects, dispersal limitation, environmental filtering, and speciation can all influence biodiversity at different spatial and temporal scales. A key thrust of this work is to develop a phenomenological model to explain variation in the slope of the species-area relationship.

• Storch, D., P. A. Marquet, and J. H. Brown, eds. 2007. Scaling biodiversity. Cambridge, UK: Cambridge Univ. Press.

  This edited book provides examples of several different approaches to modeling the scaling of biodiversity and provides a reference point for how the discipline transformed from niche versus neutral camps to a more unified vision of ecology (see Vellend 2016 and Leibold and Chase 2017). This book is also a useful reference for Palmer’s environmental texture hypothesis, Harte’s hypothesis of equal allocation probabilities, and Sizling’s random clustering model of spatial invariance.

• Vellend, M. 2016. The theory of ecological communities. Princeton, NJ: Princeton Univ. Press.

  DOI: 10.1515/9781400883790

  Vellend argues that generality about community assembly may be observable if we focus on just four high-level processes: ecological drift (i.e., random loss of species due to demographic stochasticity), selection (i.e., competition and environmental filtering), dispersal, and speciation. Vellend reviews the evidence for each mechanism and suggests tests that need to be carried out to move the field forward. This book promises to change the way community ecology is taught at all levels.