Metacommunities: Spatial Dynamics and Ecological Communities

by Marcel Holyoak, Mathew A. Leibold, Robert D. Holt

Overview

Until recently community ecology—a science devoted to understanding the patterns and processes of species distribution and abundance—focused mainly on specific and often limited scales of a single community. Since the 1970s, for example, metapopulation dynamics—studies of interacting groups of populations connected through movement—concentrated on the processes of population turnover, extinction, and establishment of new populations.

Metacommunities takes the hallmarks of metapopulation theory to the next level by considering a group of communities, each of which may contain numerous populations, connected by species interactions within communities and the movement of individuals between communities. In examining communities open to dispersal, the book unites a broad range of ecological theories, presenting some of the first empirical investigations and revealing the value of the metacommunity approach.

The collection of empirical, theoretical, and synthetic chapters in Metacommunities seeks to understand how communities work in fragmented landscapes. Encouraging community ecologists to rethink some of the leading theories of population and community dynamics, Metacommunities urges ecologists to expand the spatiotemporal scales of their research. 

Product Details

ISBN-13:	9780226350646
Publisher:	University of Chicago Press
Publication date:	10/01/2005
Edition description:	New Edition
Pages:	520
Product dimensions:	6.00(w) x 9.00(h) x 1.40(d)

About the Author

Marcel Holyoak is professor in the Department of Environmental Science and Policy at the University of California, Davis.


Mathew A. Leibold is professor in the Department of Integrative Biology at the University of Texas.


Robert D. Holt is professor of ecology at the University of Florida.

Read an Excerpt

METACOMMUNITIES
Spatial Dynamics and Ecological Communities
The University of Chicago Press
Copyright © 2005
The University of Chicago
All right reserved.

ISBN: 978-0-226-35064-6


Chapter One Metacommunities A Framework for Large-Scale Community Ecology

Marcel Holyoak, Mathew A. Leibold, Nicolas Mouquet, Robert D. Holt, and Martha F. Hoopes

A primary goal of ecology is to measure, understand, and predict patterns of biodiversity, including the numbers of kinds of organisms and their genetic and phenotypic or functional diversity. Patterns in the distribution and abundance of species are often striking, inspiring awe of nature and fostering a desire to conserve biodiversity. Understanding such patterns has crucial practical utility, for instance as part of the ongoing quest to understand the role of biodiversity in ecosystem functioning (e.g., maintaining water quality, atmospheric C[O.sub.2] levels, or primary production; Naeem et al. 1999; Loreau 2000). Dealing with anthropogenic global change provides a strong motivation to articulate the mechanisms creating and maintaining biodiversity.

Biodiversity is structured by processes operating at several hierarchical scales, including populations of individual species, interacting populations of different species (predators and prey, competitors, etc.), and whole communities and ecosystems (e.g., indirect interactions, levels of ecosystem functioning). The patterns of biodiversity that we seek to understand are also innately spatial, scaling from local ecosystems to landscapes and entire biogeographic regions (e.g., Wiens 1989; Levin 1992; Holt 1993; Rosenzweig 1995; Maurer 1999; Hubbell 2001; Chase and Leibold 2003). Surprisingly, there are many gaps in the empirical and theoretical knowledge that could logically explain the dynamics of entire communities in spatially structured habitats (e.g., collections of fragments). This book aims at filling some of these gaps by highlighting the emergence of a new focus for ecologists working at this level of organization-what is known as "metacommunity ecology."

The kinds of patterns we seek to explain are established by existing empirical studies, for instance, by studies that measure species diversity locally (a-diversity), among-localities (b-diversity) and regionally (g-diversity; Whittaker 1960; Magurran 1988). Especially interesting are cases where such patterns of diversity are linked to changes in composition and related to environmental factors such as environmental gradients. We argue that a complete theory for species diversity would have the potential, as is appropriate for the study system, to explain the following:

How diversity varies at different scales ranging from that of single point samples, through elements of spatial and temporal turnover over different scales, to the regional scale. Most community theory is focused on the "local" scale and much less thought has gone into explaining diversity at other scales (e.g., Pimm 1982; Polis and Winemiller 1996; Morin 1999).

How diversity is related to other major features of communities and ecosystems such as trophic structure (allocation of biomass into different functional groups), and rates of flow of materials through food webs and ecosystems. Again, much of "diversity theory" (e.g., Whittaker 1960; MacArthur and Wilson 1967; Magurran 1988) is focused on explaining patterns in the number of species without relating this to the ways these species participate in other important ecological processes.

How patterns of diversity at different scales are related to processes involving dispersal as it affects either colonization rates (rates of introduction of novel species into communities where they were previously absent) or population dynamics per se (frequently involving mass effects, rescue effects or source-sink relations among different local communities-see table 1.1 for definitions of italicized words). While much recent work has explored the effects of dispersal in a piecemeal fashion there is still much to do to understand the full spectrum of dispersal-mediated dynamics that might occur among interacting species at different spatial and temporal scales. This question builds on the foundations of island biogeography and metapopulation theory (e.g., MacArthur and Wilson 1967; Hanski and Gilpin 1997; Hanski and Gaggiotti 2004).

This book aims to begin to provide a body of work that can address all of these questions in a unified way. We encourage readers to think broadly about the kinds of empirical, theoretical and synthetic work that can contribute to understanding species diversity and the spatial structure of communities, coalescing around the theme of metacommunities.

During the last few years ecologists have increasingly questioned whether the existing conceptual framework of community ecology is adequate for describing the dynamics of communities that are connected across space. The metacommunity concept has emerged as a new and exciting way to think about spatially-extended communities. It leads us to ask novel questions about the mechanisms that structure ecological communities and that create emergent patterns, such as patterns of species diversity and distribution. A metacommunity can be defined as a set of local communities that are linked by dispersal (Hanski and Gilpin 1991; Wilson 1992; table 1.1). In turn, a community may be defined as a collection of species occupying a particular locality or habitat. These definitions describe a hierarchy of scales and emphasize the ways in which processes occurring at smaller scales interact with those at larger scales (e.g., Levins and Culver 1971; Vandermeer 1973; Crowley 1981; Law et al. 2000; Mouquet and Loreau 2002). It is these interactions among processes at different spatial scales that are central to metacommunity thinking and that form the core of this book.

This introductory chapter has five purposes. First, we elaborate on the motivation for studying metacommunities. Second, we flesh out the metacommunity concept by building on the definitions above. Third, we provide a set of definitions in table 1.1 that facilitate discussion. Fourth, we describe four conceptual models that help to simplify thinking about metacommunities (following Leibold et al. 2004). Fifth, we highlight the variety of ways in which metacommunities are being studied by introducing the rest of this book.

The Need for the Metacommunity Concept

This book arose because of empirical and theoretical gaps in the ecological literature that could limit the success of both pure and applied ecology. This section describes some problems that indicate the need to consider the spatial dynamics of communities.

A good example of a classical community ecology concept that has been misleading because of our failure to explicitly consider space is the intermediate disturbance hypothesis (IDH) (Connell 1978). The IDH is the most frequently cited nonequilibrium mechanism of species coexistence (Wilson 1990), and predicts that species diversity will be greatest at intermediate levels of disturbance. In thirty-six empirical studies (Shea et al. 2004), what counted as "intermediacy" of disturbance was defined in terms of intensity (seventeen cases), frequency (thirteen cases), time since disturbance (three cases), extent (two cases), and duration (one case). However, of twenty-seven published empirical tests of the IDH, only ten (37%) showed the predicted relationship of maximum species diversity at intermediate disturbance (Holyoak, unpublished data). Furthermore, Roxburgh et al. (2004) pointed out that disturbance per se is not the coexistence mechanism involved in the IDH. Instead the storage effect and relative nonlinearity (see table 1.1 and Hoopes et al., chapter 2 for further explanation) are the mechanisms of coexistence; these may be independent of disturbance in many systems. The lack of congruency with the IDH in many empirical tests is therefore not surprising because disturbance is not necessarily the mechanism of coexistence even when disturbance influences communities! Roxburgh et al. (2004) made possible the identification of coexistence mechanisms by searching for indicators of relative nonlinearities and the storage effect within spatially explicit models. In a lucid review of empirical studies, Shea et al. (2004) began the search for such mechanisms and clarified the role of disturbance in nature. Our initial ideas about the IDH (e.g., Connell 1978), and their recent reinterpretation (Roxburgh et al. 2004; Shea et al. 2004), are a good example of where taking a closer look at spatial dynamics has led to important new insights.

A second motivation for studying metacommunities comes from our desire to conserve biodiversity in landscapes experiencing fragmentation. Habitat fragmentation creates patchy landscapes in which dispersal may be required for persistence, and is acknowledged to be an important factor driving the loss of biodiversity (e.g., Wilcove et al. 2000). However, fragmentation studies typically use empirical trends to predict how communities will change during fragmentation because we lack a general metacommunity theory to guide us in how to measure and analyze natural fragmented communities. In a recent book on forest fragmentation and management, Lindenmayer and Franklin (2002) recount a large number of examples where fragmentation produced largely unexpected effects either on individual species or biodiversity. Experimental studies of fragmentation also frequently produce "surprising" effects (Debinski and Holt 2000). Unexpected effects took a variety of forms, but commonly observed phenomena were that fragmentation responses were influenced by the nature of the habitat "matrix" between patches (see also Davies et al., chapter 7), and by changes in habitat within patches (e.g., edge effects). Empirical work on fragmentation often investigates the ability of species' traits to predict responses to fragmentation, but rarely attempts to explicitly deal with community structure (metacommunity studies, such as those in this book, are exceptions to this generalization). Metapopulation models provide a motivation for studying species interactions within communities. Single species are equivalent to noninteracting species and specialist predators and prey or competitors exemplify interacting species. In single species metapopulation models, the subdivision of habitat that results from fragmentation can only be detrimental-as fragmentation proceeds, previously stable populations in large undivided habitats become increasingly small and isolated, making them vulnerable to local extinction through demographic stochasticity, but with a reduced capacity for patches to be to be recolonized (Harrison and Taylor 1997). For interacting pairs of species, where a species can drive another locally extinct, persistence and diversity can actually be enhanced by fragmentation (subdivision). This may occur as formerly extinction-prone interacting populations in large areas of habitat become fragmented and various spatial dynamics (e.g., colonization-competition trade-offs, see table 1.1) become possible that can enhance persistence and diversity (Harrison and Taylor 1997; Hoopes et al., chapter 2). The degree to which species negatively interact could therefore be critical to the way in which species respond to fragmentation. It is an open question whether the responses of biodiversity to fragmentation are best predicted using community-level theory (metacommunities) or species-level theory (metapopulations), and the answer is likely to depend on the degree to which species interact, on how such interactions are modified by spatial dynamics, and by how such pair-wise interactions are embedded in more complex multispecies communities.

The absence of a theory that provides mechanisms for responses to fragmentation potentially limits both our ability to predict how communities will change under altered circumstances and our ability to effectively manage communities and metacommunities by manipulating habitat factors at landscape scales. Since the most general goal of conservation efforts is to maintain biodiversity, it is worrying that we at present attempt this without a complete theory that can explain the maintenance of biodiversity over ecologically relevant periods of time. These deficiencies in knowledge also carry over to managing fisheries through protecting areas in marine reserves, to restoring habitats where placement of restoration sites is an issue, to managing invasive (and spreading) species, to predicting the impacts of climate change, and to managing ecosystem properties that are linked to biodiversity.

A specific example helps provide motivation for studying the role of community-level mechanisms and especially species interactions in understanding responses to habitat fragmentation (Allan et al. 2003; LoGiudice et al. 2003). Forest fragmentation and habitat destruction in Dutchess County (NY, USA) have been shown to reduce mammalian species diversity and to elevate population densities of white-footed mice (Peromyscus leucopus). Fragmentation is also expected to cause an increase in the human exposure to Lyme disease because the disease's vector, black-legged ticks (Ixodes scapularis), are more likely to be infected with the Lyme bacterium (Borrelia burgdorferi) after feeding on mice compared to other vertebrate hosts. The frequency of tick infection declined linearly as fragment area increased, while mammalian species diversity increased, and mice density declined (Allan et al. 2003). Different vertebrate species have been shown to harbor different numbers of ticks, leading to different survival rates of ticks and different infection rates of ticks with the Lyme bacterium. White-footed mice are overwhelmingly the greatest producers of infected ticks, and the ability of mice to produce ticks is different for the various vertebrate hosts (figure 1.1; LoGiudice et al. 2003). Squirrels (Sciurus carolinensis and Tamiasciurus hudsonicus) are estimated to have the greatest combined effects in reducing the potential for Lyme disease (figure 1.1) (because of mechanisms like competition between vertebrate host species and tick preference for different hosts). Several questions follow from these observations, and all of them are likely to require spatial answers: (1)What are the implications of the differences among vertebrate hosts and differences in the sequence of community assembly for the occurrence of Lyme disease (LoGiudice et al. 2003)? Community assembly in fragments results from the movement of species between fragments (a spatial dynamic). (2) Are vertebrate hosts responding directly to habitat change or are they undergoing indirect changes caused by interactions with other species? This question is also central to testing the "species sorting perspective" of metacommunities sketched later in this chapter. (3) How do species interactions between the Lyme bacterium, the tick and vertebrate hosts operate? Predator-prey and host-disease metapopulation models show the potential for these interactions to be strongly influenced by spatial dynamics (see Hoopes et al. chapter 2, and Holt and Hoopes, chapter 3).

These examples illustrate substantial gaps in our knowledge that require examination of the role of spatial structure and dynamics in ecological communities. This book provides many further examples of problems that motivate the study of metacommunities. The caveats introduced into various pieces of work show that we are just beginning on a journey of discovery. This volume is intended to provide for a broad community of basic and applied ecologists the essential conceptual building blocks for further exploration of metacommunities.

Defining Metacommunities

Earlier we defined a metacommunity as a set of local communities that are linked by dispersal (Hanski and Gilpin 1991; Wilson 1992), and a community as a collection of species occupying a particular locality or habitat (table 1.1). This set of definitions works well for conceptualizing metacommunities, but is often complicated by the complex nature of real metacommunities. This section discusses some of these complexities, first for communities then for metacommunities.

(Continues...)

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Table of Contents

Preface and Acknowledgments
Introduction
1. Metacommunities: A Framework for Large-Scale Community Ecology
Marcel Holyoak, Mathew A. Leibold, Nicolas M. Mouquet, Robert D. Holt, and Martha F. Hoopes
Part 1: Core Concepts
Introduction by Marcel Holyoak
2. The Effects of Spatial Processes on Two Species Interactions
Martha F. Hoopes, Robert D. Holt, and Marcel Holyoak
3. Food Web Dynamics in a Metacommunity Context: Modules and Beyond
Robert D. Holt and Martha F. Hoopes
Part 2: Empirical Perspectives
Introduction by Marcel Holyoak and Robert D. Holt
4. Metacommunities of Butterflies, Their Host Plants, and Their Parasitoids
Saskya van Nouhuys and Ilkka Hanski
5. Inquiline Communities in Pitcher Plants as a Prototypical Metacommunity
Thomas E. Miller and Jamie M. Kneitel
6. Local and Regional Community Dynamics in Fragmented Landscapes: Insights from a Bryophyte-based Natural Microcosm
Andrew Gonzalez
7. Metacommunity Structure Influences the Stability of Local Beetle Communities
Kendi F. Davies, Brett A. Melbourne, Chris R. Margules, and John F. Lawrence
8. Local Interactions and Local Dispersal in a Zooplankton Metacommunity
Karl Cottenie and Luc De Meester
9. Assembly of Unequals in the Unequal World of a Rock Pool Metacommunity
Jurek Kolasa and Tamara N. Romanuk
Part 3: Theoretical Perspectives
Introduction by Richard Law and Priyanga Amarasekare
10. The World Is Patchy and Heterogeneous! Trade-off and Source-Sink Dynamics in Competitive Metacommunities
Nicholas Mouquet, Martha F. Hoopes, and Priyanga Amarasekare
11. Assembly Dynamics in Metacommunities
Richard Law and Mathew Leibold
12. Scale Transition Theory for Understanding Mechanisms in Metacommunities
Peter Chesson, Megan J. Donahue, Brett A. Melbourne, and Anna L. W. Sears
13. Applying Scale Transition Theory to Metacommunities in the Field
Brett A. Melbourne, Anna L. W. Sears, Megan J. Donahue, and Peter Chesson
Part 4: Emerging Areas and Perspectives
Introduction by Marcel Holyoak and Mathew Leibold
14. Competing Theories for Competitive Metacommunities
Jonathan M. Chase, Priyanga Amarasekare, Karl Cottenie, Andrew Gonzalez, Robert D. Holt, Marcel Holyoak, Martha F. Hoopes, Mathew A. Leibold, Michel Loreau, Nicolas Mouquet, Jonathan B. Shurin, and David Tilman
15. Assembling and Depleting Species Richness in Metacommunities: Insights from Ecology, Population Genetics, and Macroevolution
Mark A. McPeek and Richard Gomulkiewicz
16. Habitat Selection, Species Interactions, and Processes of Community Assembly in Complex Landscapes: A Metacommunity Perspective
William J. Resetarits, Jr., Christopher A. Binckley, and David R. Chalcraft
17. New Perspectives on Local and Regional Diversity: Beyond Saturation
Jonathan B. Shurin and Diane S. Srivastava
18. From Metacommunities to Metaecosystems
Michel Loreau, Nicolas Mouquet, and Robert D. Holt
19. Adaptive and Coadaptive Dynamics in Metacommunities: Tracking Environmental Change at Different Spatial Scales
Mathew A. Leibold, Robert D. Holt, and Marcel Holyoak
20. Future Directions in Metacommunity Ecology
Robert D. Holt, Marcel Holyoak, and Mathew A. Leibold
Coda by Marcel Holyoak, Mathew A. Leibold, and Robert D. Holt
List of Contributors
Index

Editorial Reviews

"[The book] deserves a wide readership among community ecologists, scholars of ecosystem ecology and related disciplines."

History of Philosophy and Life Science - Matthias Gross

"The material is clearly presented and the quality of writing is generally high. In its liberal use of tables and diagrams, the book serves as an excellent introduction to the foundational concepts and theoretical lineage of metacommunity theory. It certainly is an excellent choice for a graduate seminar."

Ecology - Michael M. Fuller

"The book presents a compelling case for adding the metacommunity concept to the ecologocial toolbox. I suggest that you add it to your bookshelf. . . . My personal standard for a book is that it changes how I think about a subject. This book met this criterion. Metacommunities makes an excellent case that metacommunity theory is not just metapopulation theory for the 00s. Substantially different dynamics from those predicted in metapopulation models result when dispersal enmeshes the local dynamics of multiple interacting species. I believe the book will encourage readers to understand how regional linkages affect local ecological outcomes in their own systems."

Conservation Biology - Mark C. Urban

"This book is a resoundingly thorough exploration of metacommunity concepts to date. . . . An exciting and valuable compilation of ideas that will strengthen this rapidly growing field."

Austral Ecology - Don A. Driscoll

"This book is timely, scholarly, stimulating, and a major step toward a fully unfied community ecology. It is a must-read for anyone trying to understand diversity and structure of biotic communities."

Ecoscience - Hans Henrik Bruun