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The Theory of
Ecological Communities

MONOGRAPHS IN POPULATION BIOLOGY
EDITED BY SIMON A. LEVIN AND HENRY S. HORN
A complete series list follows the index.

The Theory of
Ecological Communities
Mark Vellend
Princeton University Press
Princeton and Oxford

Copyright © 2016 by Princeton University Press
Published by Princeton University Press, 41 William Street, Princeton, New Jersey 08540
In the United Kingdom: Princeton University Press, 6 Oxford Street, Woodstock,
Oxfordshire OX20 1TW
press.princeton.edu
All Rights Reserved
Library of Congress Cataloging-in-Publication Data
Names: Vellend, Mark, 1973– , author.
Title: The theory of ecological communities / Mark Vellend.
Description: Princeton : Princeton University Press, 2016. | Series: Monographs in
population biology | Includes bibliographical references and index.
Identifiers: LCCN 2015047633 | ISBN 9780691164847 (hardcover : alk. paper)
Subjects: LCSH: Biotic communities.
Classification: LCC QH541 .V425 2016 | DDC 577.8/2—dc23 LC record available
at https://lccn.loc.gov/2015047633
British Library Cataloging-in-Publication Data is available
This book has been composed in Times LT Standard
Printed on acid-free paper. ∞
Printed in the United States of America
10 9 8 7 6 5 4 3 2 1

Contents
Acknowledgments vii
1. Introduction 1
PART I
APPROACHES, IDEAS, AND
THEORIES IN COMMUNITY ECOLOGY
2. How Ecologists Study Communities 9
3. A Brief History of Ideas in Community Ecology 20
PART II
THE THEORY OF ECOLOGICAL COMMUNITIES
4. The Pursuit of Generality in Ecology and Evolutionary Biology 39
5. High-Level Processes in Ecological Communities 49
6. Simulating Dynamics in Ecological Communities 69
PART III
EMPIRICAL EVIDENCE
7. The Nature of Empirical Evidence 93
8. Empirical Evidence: Selection 107
9. Empirical Evidence: Ecological Drift and Dispersal 138
10. Empirical Evidence: Speciation and Species Pools 158
PART IV
CONCLUSIONS, REFLECTIONS, AND FUTURE DIRECTIONS
11. From Process to Pattern and Back Again 175
12. The Future of Community Ecology 182
References 193
Index 225

Acknowledgments
The ideas in this book, and the inspiration and encouragement to develop them,
have come from many and various sources. As the saying goes, we are often
able to move science forward because we are “standing on the shoulders of
giants.” In my case, I have been extremely fortunate to cross paths with many
great scientific minds whose collective influence on my thinking cannot be
overstated.
First, I am greatly indebted to my scientific mentors. My first direct experi-
ence in ecological science was as a field assistant working in an old-growth for-
est on Mont Saint-Hilaire, Québec, as part of a project led by Martin Lechowicz,
Marcia Waterway, and Graham Bell of McGill University. I was part of a team
of mostly inexperienced undergraduate students ripping apart sedges in the lab
to make genetic clones and then planting these clones up and down kilometer-
long transects in the forest. We eagerly awaited visits to the field site from our
mentors—Marcia taught us how to identify everything, Graham laid out the
theoretical context, and Marty covered everything in between. Graham’s view
of the forest plants as being conceptually not so different from his test tubes of
evolving algae in the lab at first struck most of us as oversimplified to the point
of eliminating all the beauty and mystery from the natural world. But the ap-
peal of focusing on general processes where others saw a near-insurmountable
web of details stuck with me, as did Marty and Marcia’s insistence that our
theoretical models be molded to the reality of the natural world, and not vice
versa. The conceptual framework of this book is probably not so different from
the one I was first exposed to while on the “Carex crew” in the 1990s.
My PhD advisors, Peter Marks and Monica Geber, fostered deep reflection
on both empirical and theoretical perspectives in science and, perhaps more
important, provided the freedom and unwavering support to intellectually wan-
der the conceptual terrain of ecology and evolution. Stephen Ellner sparked my
interest in theory, and the clarity of his thinking remains an inspiration for me
today. One more person deserves mention here, although he might be surprised
to read this. During our first year as PhD students, Sean Mullen and I were in
the introductory biology teaching assistants’ room waiting to see if any stu-
dents would come see us, and he made an offhand comment along the lines of
“it would be super cool to know whether patterns of genetic variation in your
forest plants correspond to the community-level patterns of interest.” That one
remark helped set the direction for much of my research for the next 10 years,

viii ACKNOWLEDGMENTS
in particular my interest in integrating community ecology and population ge-
netics, which underpins the conceptual framework in this book. Thanks, Sean.
Another major source of stimulus came from Stephen Hubbell’s (2001) book
on neutral theory, which essentially represents the importation into community
ecology of one specific set of models from population genetics—those exclud-
ing selection. In some ways, the present book represents the next logical step:
the importation and addition of models involving selection. Janis Antonovics,
Bob Holt, and Joan Roughgarden have also made the basic argument that many
ecological processes are closely analogous to evolutionary processes, and per-
sonal meetings with each of these giants of ecology and evolution provided
inspiration at various points along the way.
I have probably received the most encouragement to turn my ideas into a
book from students of community ecology or fellow scientists, most of whom
were “junior,” circa 2010 or before. For providing a testing ground, critical
feedback, and substantial encouragement, I have several groups of people to
thank: the students and fellow instructors in three courses in community ecol-
ogy (two at the University of British Columbia, one at Université de Sher-
brooke); the students in my lab group, in Margie Mayfield’s lab group (Univer-
sity of Queensland), and in various discussion groups; and the many students I
have met during seminar visits in too many places to name. These students and
their successors are one of my primary target audiences.
A fellow postdoc at the National Center for Ecological Analysis and Syn-
thesis, John Orrock, was coauthor and cobrainstormer on a book chapter that
presented an initial sketch of the ideas in this book (Vellend and Orrock 2009),
and Anurag Agrawal was very supportive in inviting submission of a more de-
veloped paper to Quarterly Review of Biology (Vellend 2010). Prior or sub-
sequent to publication of the QRB paper, I received especially encouraging
and/or constructively critical comments (even if many were quite brief and
not necessarily positive) from Peter Adler, Bea Beisner, Marc Cadotte, Jérôme
Chave, Jon Chase, Jeremy Fox, Amy Freestone, Jason Fridley, Tad Fukami,
Nick Gotelli, Kyle Harms, Marc Johnson, Jonathan Levine, Chris Lortie, Brian
McGill, Jason McLachlan, Christine Parent, Bob Ricklefs, Brian Starzomski,
James Stegen, and Diego Vázquez. No doubt I am missing some important
people from this list, for which I apologize. The University of Queensland, and
my sabbatical host there, Margie Mayfield, provided an inspiring setting where
the bulk of the writing of this book was completed.
Finally, during the writing of the book I received invaluable input from many
people in the form of data, advice, or critical feedback. Raw data for analyses
and/or graphics were generously provided by Véronique Boucher-Lalonde,
Will Cornwell, Janneke HilleRisLambers and Jonathan Levine, Carmen Mon-
taña, Laura Prugh, Adam Siepielski, Josie Simonis, Janne Soininen, and Car-
oline Tucker and Tad Fukami. Feedback on particular issues or sections of the
book was provided by Jeremy Fox, Monica Geber, Dominique Gravel, Luke

ACKNOWLEDGMENTS ix
Harmon, Liz Kleynhans, Nathan Kraft, Geoffrey Legault, Jonathan Levine, and
Andrew MacDonald. Andrew MacDonald is also responsible for the presenta-
tion of R code in a much nicer format than I was capable of producing myself
and for helping my programming skills inch slightly toward the twenty-first
century (I still have a long way to go). Finally, I owe a very special thanks to
several people who read and provided excellent feedback on the book in its
entirety: Véronique Boucher-Lalonde, Bob Holt, Marcel Holyoak, Geneviève
Lajoie, Andrew Letten, Jenny McCune, Brian McGill, and Caroline Tucker.
The book is far better than it would have been without the input from all these
people, and I am profoundly grateful for the generosity of everyone who has
helped out in some way.

C H A P T E R 1
Introduction
Many budding ecologists have their imaginations captured by a seemingly sim-
ple question: why do we find different types and numbers of species in differ-
ent places? The question is the same whether the setting is birds in the forest,
plants along a mountainside, fish in lakes, invertebrates on a rocky shore, or
microbes in the human body. Some parts of the answer to this question are glar-
ingly obvious just from a short walk more or less anywhere on earth. Strolling
through any city or town in eastern North America, we can see that the plant
species growing in sidewalk cracks and dry roadsides are different from those
growing in wet ditches, which are different still from those growing in wooded
parks. Some birds reach very high abundance in dense urban areas, while oth-
ers are found exclusively in wetlands or forests. So, we can observe everyday
evidence that environmental variation selects for different species in different
places (Fig. 1.1).
As we begin to look more closely, however, the story is not so simple. Some
places that seem to present near-identical environmental conditions are none-
theless home to very different sets of species. Some pairs of species seem to
live in very similar types of environments but almost never in the same phys-
ical place. Two places experiencing a very similar disturbance event (e.g., a
drought or fire) subsequently follow very different successional trajectories.
A hectare of one type of forest might contain 100-fold more species than a
hectare of another type of forest. A major scientific challenge is thus to devise
theories that can explain and predict such phenomena. Over the past 150 years
ecologists have risen to this challenge, devising hundreds of conceptual or the-
oretical models that do just this. However, because almost every such model

2 CHAPTER 1
is relevant to at least one type of community somewhere on earth, the list of
explanations for community patterns gets only ever longer, never shorter.
We are thus faced with a serious pedagogical challenge: how to conceptually
organize theoretical ideas in community ecology as simply as possible to fa-
cilitate ecological understanding. We have for a long time organized ecological
knowledge (in textbooks or other synthetic treatments) according to subareas
into which researchers have self-organized rather than fundamental ecological
processes that cut across these subareas. For example, a treatment of plant com-
munity ecology might have sections on herbivory, competition, disturbance,
stress tolerance, dispersal, life-history tradeoffs, and so on (Crawley 1997,
Gurevitch et al. 2006). Similarly, a conceptual treatment of community ecology
might present many competing theories: island biogeography, priority effects,
colonization-competition models, local resource–competition theory, neutral
theory, metacommunity theory, and so on (Holyoak et al. 2005, Verhoef and
Morin 2010, Morin 2011, Scheiner and Willig 2011, Mittelbach 2012). As a
result, if each student in an undergraduate or graduate class is asked to write
down a list of processes that can influence community composition and diver-
sity (I have done this several times), the result will be a long list from each
student, and collectively no fewer than 20–30 items.
The central argument to be developed in this book is as follows. Underlying
all models of community dynamics are just four fundamental, or “high-level,”
processes: selection (among individuals of different species), ecological drift,
dispersal, and speciation (Vellend 2010). These processes parallel the “big
four” in evolutionary biology—selection, drift, migration, and mutation—and
they allow us to organize knowledge in community ecology in a simpler way
than by using the conventional approach. What seems like a jumble of inde-
pendent theoretical perspectives can be understood as different mixtures of a
Figure 1.1. The east-facing slope of Mont Saint-Joseph in Parc national du Mont Mé-
gantic, Québec, illustrating spatial relationships between environmental conditions and
community composition. The cold, upper part of the slope (~850–1100 m above sea
level) is boreal forest (dark coloration) dominated by balsam fir (Abies balsamea). The
lower slope is deciduous forest (light coloration) dominated by sugar maple (Acer sac-
charum). The photo was taken in springtime (8 May 2013), prior to the flushing of de-
ciduous leaves. The foreground is relatively flat terrain (~400 m a.s.l.) composed mostly
of a patchwork of young forest stands on private land, with a variety of different tree
species. From left to right, the image spans roughly 4 km.

INTRODUCTION 3
few basic ingredients. By articulating a series of hypotheses and predictions
based on the action of these four processes, we can thus build a general theory
of ecological communities. As explained further in Chapter 2, the theory does
not apply equally to all topics under the broad umbrella of community ecol-
ogy. For example, models of species on the same trophic level interacting via
competition and/or facilitation (sometimes called “horizontal” communities)
fall cleanly within the theory, whereas models involving trophic interactions fit
within the theory largely to the extent that they make predictions concerning
properties of horizontal components of the larger food web (which they often
do). Nonetheless, following the tradition set by MacArthur and Wilson (1967,
The Theory of Island Biogeography) and Hubbell (2001, The Unified Neutral
Theory of Biodiversity and Biogeography), I call my theory and therefore my
book The Theory of Ecological Communities.
1.1. WHAT THIS BOOK IS
My overarching objective in this book is to present a synthetic perspective on
community ecology that can help researchers and students better understand
the linkages among the many theoretical ideas in the field. The initial sketch of
these ideas was presented in Vellend (2010), and this book is a fully fleshed-out
version of the theory, reiterating the key points of the earlier paper but going
well beyond it in many ways:
• First, I more thoroughly place the theory of ecological communities in
historical context (Chap. 3), and I present a novel perspective (gleaned
from philosopher Elliott Sober) on why high-level processes (in this case
selection, drift, dispersal, and speciation) represent an especially appropri-
ate place to seek generality in community ecology (Chap. 4).
• I describe in detail how a vast number of different hypotheses and models in
community ecology fit as constituents of the more general theory (Chap. 5).
• I provide simple computer code in the R language that (i) generates predic-
tions for empirical testing, (ii) illustrates how changing a few basic “rules”
of community dynamics reproduces a wide range of well-known models,
and (iii) allows readers to explore such dynamics on their own (Chap. 6).
• After outlining some key motivations and challenges involved in empirical
studies in ecology (Chap. 7), I then put the theory of ecological communi-
ties to work by systematically articulating hypotheses and predictions based
on the action of selection (Chap. 8), drift and dispersal (Chap. 9), and speci-
ation (Chap. 10), in each case evaluating empirical evidence supporting (or
not) the predictions. In essence, Chapters 8–10 serve to reframe the corpus
of empirical studies in community ecology according to a general theory
that is considerably simpler than typically found in a textbook treatment
of the discipline.

4 CHAPTER 1
• Chapters 11 and 12 present some overarching conclusions and a look to
the future.
1.1.1. Reading This Book as a Beginner, an Expert, or Something in Between
This book is aimed at senior undergraduate students, graduate students, and
established researchers in ecology and evolutionary biology. It is the book I
would have liked to read during grad school. I believe it presents the core con-
ceptual material of community ecology in a new and unique way that makes it
easier to grasp the nature of the key processes underlying community dynam-
ics and how different approaches fit together. This has been my experience in
using it as a teaching tool. I also hope to stimulate established researchers to
think about what they do from a different perspective, and perhaps to influence
how they teach community ecology themselves. Thus, I approached the writing
of the book with the dual goals of pedagogy (beginning-student audience) and
advancing a new way of thinking about theory in community ecology (expert au-
dience). I suspect that readers who are somewhere on the pathway from beginner
to expert—that is, grad students—have the most to gain from reading this book.
A pervasive challenge in scientific communication (including teaching) is to
keep the most knowledgeable members of an audience engaged without “los-
ing” those with the least preexisting knowledge of the topic. Readers can get
the most out of this book if they are already somewhat familiar with the kinds
of community-level patterns of species diversity and composition that ecolo-
gists aim to explain, as well as some of the factors commonly invoked to ex-
plain such patterns—environmental conditions, competition, disturbance, and
so on. I begin explanations at a fairly basic level and provide what I consider
the essential background (Chaps. 2–3), but even so, a full understanding of
various historical advances in ecology (Chap. 3) and some of the more sophis-
ticated empirical studies (Chaps. 8–11) requires delving into the primary liter-
ature. At the other end of the spectrum, expert readers will no doubt encounter
sections they can skim, but I hope that all chapters of the book contain enough
novel perspectives, approaches, or modes of traversing well-trodden ground to
engage even the most expert reader. If you are an expert and pressed for time,
you may choose to skip to the end of Chapter 3 (Sec. 3.4), where I begin the
transition from background material to the details of my own distinct perspec-
tive and theory. Feedback on earlier versions of the book suggested that experts
will find the most “new stuff” in the latter part of the book (Chaps. 8–12).
1.1.2. Unavoidable Trade-Offs
This book covers a very broad range of topics (models, questions, methods,
etc.), which necessarily involves a trade-off with detail in several respects.
First, the depth to which I explore each individual topic is limited. So, while

INTRODUCTION 5
readers will learn, for example, about the strengths and weaknesses of differ-
ent approaches to testing for signatures of ecological drift or spatially variable
selection, they will not learn all the detailed ins and outs of how to implement
particular empirical methods. I am not myself an expert on all such details, and
even for topics I do know quite well, I have deliberately limited the detail so as
not to distract from the big-picture conceptual issues on which I want to focus.
Plenty of references are provided for readers interested in digging deeper. Sec-
ond, I present very few formal statistics, despite their ubiquity in ecological
publications. I report a great many empirical results from the literature, but
almost entirely in graphical form, allowing readers to see for themselves the
patterns in the data. Interested readers can consult the original publications for
p-values, slopes, r2
, AIC, and the like. Finally, I cannot claim to have cited the
original paper(s) on all topics. My emphasis has been on communicating the
ideas rather than tracing each of their histories to the origin, although I do ded-
icate a whole chapter to the history of ideas, and I hope I have managed to give
credit to most of those papers considered “classics” by community ecologists.
1.1.3. Sources of Inspiration
By way of ensuring that I have appropriately credited the ideas that form the
basic premise of this book, I end this introductory chapter by acknowledging
those publications that inspired me by calling attention to the striking con-
ceptual parallels between population genetics and community ecology (An-
tonovics 1976, Amarasekare 2000, Antonovics 2003, Holt 2005, Hu et al.
2006, Roughgarden 2009). Many additional researchers have taken notice of
these parallels, especially following the importation into ecology of neutral
theory from population genetics (Hubbell 2001). That said, I can say from ex-
perience that most community ecologists have not thought of things in this
way, and there has been no systematic effort to find out whether it’s possible to
reframe the bewildering number of theories, models, and ideas in community
ecology as constituents of a more general theory involving only four high-level
processes. This book is my attempt to do so.

P a r t I
APPROACHES, IDEAS, AND THEORIES
IN COMMUNITY ECOLOGY

C H A P T E R 2
How Ecologists Study Communities
The next three chapters serve three main purposes: (i) to establish the domain
of application of the theory of ecological communities, (ii) to describe the basic
community patterns of interest, and (iii) to place the book in historical context.
The present chapter is aimed largely at goals (i) and (ii), but as a by-product it
also begins to address goal (iii). Historical context is addressed more fully in
Chapters 3 and 4.
Ecologists study communities in a variety of ways. In the very same study
system (e.g., temperate lakes), one ecologist might focus on the phytoplankton
community, while another focuses on the interaction between zooplankton and
a dominant fish species. One study might focus on the processes that determine
community structure in a single lake, while another describes patterns across
several lakes in one landscape, or in thousands of lakes across an entire con-
tinent. Finally, one researcher might be primarily interested in understanding
why lakes vary according to how many species they contain, while another is
more interested in why lakes vary according to which species they contain.
Thus, any study in community ecology must establish from the outset at least
three things: the focal set of species, the spatial scale of analysis, and the com-
munity properties of interest. The following two sections establish the domain
of application of the theory of ecological communities according to the deline-
ation of a focal set of species (Sec. 2.1) and spatial scales of interest (Sec. 2.2).
Relative to the traditional view of community ecology focused on interactions
between species at a local scale (Morin 2011), the domain of application here is
in one sense narrower (focusing largely on single trophic levels) and in another
sense broader (focusing on all scales of space and time). Having established

10 CHAPTER 2
the domain of application, I then describe the properties of communities that
ecologists strive to understand (Sec. 2.3).
2.1. DIFFERENT WAYS OF DELINEATING
ECOLOGICAL COMMUNITIES
All scientific endeavors must define their objects of investigation, and so com-
munity ecologists must define their ecological communities. As a theoretical
ideal, it is useful to consider the complete set of organisms belonging to all spe-
cies (viruses, microbes, plants, animals) living in a particular place and time as
an ecological community sensu lato (Fig. 2.1a). In practice, however, this the-
oretical ideal is almost never met. Researchers more or less always begin their
studies by focusing on a subset of the full community, chosen on the basis of
taxonomy, trophic position, or particular interactions of interest (Morin 2011).
Recognizing the many ways researchers delimit communities, we can use the
maximally inclusive definition of a community as “a group of organisms rep-
resenting multiple species living in a specified place and time” (Vellend 2010;
see also Levins and Lewontin 1980). Once a researcher has chosen a group of
organisms as the focal community, all other components of the ecosystem—
biotic and abiotic— are then conceptually externalized, in the sense that they
may be ignored completely, or incorporated into an investigation as variables
that may influence the object of study, without being formally a part of the
object of study itself (Fig. 2.1).
Focal groups of species to be included in a community of interest can be de-
fined in many ways. Some of the earliest studies in community ecology treated
“plant communities” (Clements 1916) and “animal communities” (Elton 1927)
as separate, if interacting, objects of study. In contemporary ecology, studies
of “food webs” (McCann 2011) focus on feeding relationships, often ignoring
differences among species within trophic groups, and externalizing nonfeeding
interactions and even some feeding interactions (e.g., nectar consumption by
pollinating insects) (Fig. 2.1b). Studies of “mutualistic networks” (Bascompte
and Jordano 2013) focus on two sets of interacting species, such as plants and
their pollinators or mycorrhizae, externalizing everything else (Fig. 2.1c).
Studies also often focus on a small number of strongly interacting species—
“community modules” sensu Holt (1997)—such as particular consumer-
resource pairs (e.g., the lynx and the hare) (Fig. 2.1d).
Finally, one can choose to focus on species at a particular trophic level (e.g.,
plants)orinaparticulartaxon(e.g.,birdsorinsects),againexternalizingeverything
else (Fig. 2.1e). Ecologists have referred to such a unit of study (or something like
it) as an “assemblage” (Fauth et al. 1996), a “guild” (Root 1967), a set of “species
having similar ecology” (Chesson 2000b), or a “horizontal community” (Loreau
2010). These terms are all decidedly lacking in the pizazz and the admirable self-

HOW ECOLOGISTS STUDY COMMUNITIES 11
defining quality of the other terms in Figure 2.1, so throughout this book, for lack
of a better term, I will simply refer to them as ecological communities and, occa-
sionally, horizontal communities when the distinction is helpful.
2.1.1. A Focus on Horizontal Ecological Communities
The theory of ecological communities applies unambiguously to horizontal
ecological communities, and so this book is largely about horizontal commu-
nities, which are also the focus of a sizeable proportion of studies in ecology
as a whole (see Chap. 7). I am a plant ecologist, and my empirical studies in
community ecology focus on the set of plant species found in different places
and at different times (e.g., Vellend 2004; Vellend et al. 2006, 2007, 2013). This
is the bias I bring to the table, and not surprisingly, the theory I will describe
applies nicely to plant communities. However, it applies equally to any set of
species sharing common needs in terms of resources or space, such as phyto-
plankton, sessile intertidal invertebrates, seed eaters, decomposers, predatory
insects, or songbirds. Importantly, species in such communities interact not
only via competition, which has traditionally received the most attention from
ecologists, but also via facilitation (positive interactions) and any number of
positive or negative indirect interactions via other biotic or abiotic components
of the ecosystem (Holt 1977, Ricklefs and Miller 1999, Krebs 2009). The the-
ory here is not just about competition.
Within horizontal communities, individuals of different species share similar
abiotic and biotic constraints on fitness, and community dynamics are closely
analogous to the evolutionary dynamics of genotypes in a single species’ pop-
ulation (Nowak 2006; see also Chap. 5). Fitness can be quantified in a com-
parable way across individuals of the same or different species, and so many
theoretical models from population genetics apply just as easily to species in
communities as they do to alleles or genotypes in populations (Molofsky et
al. 1999, Amarasekare 2000, Norberg et al. 2001, Vellend 2010). Such models
are based on just four high-level processes: selection, drift, mutation, and gene
flow in population genetics; selection, drift, speciation, and dispersal in com-
munity ecology. For objects of study that include multiple trophic levels, one
can still identify the same four high-level processes, but the analogy is weaker.
Synthetic treatments have already appeared in this very monograph series on
food webs (McCann 2011), mutualistic networks (Bascompte and Jordano 2013),
and consumer-resource interactions (Murdoch et al. 2013). The present book com-
pletes the picture in Figure 2.1 by providing a conceptual synthesis of the literature
onhorizontalecologicalcommunities.Ibuildonpreviousmonographsthathavecov-
ered particular models and theories in horizontal community ecology (MacArthur
and Wilson 1967, Tilman 1982, Hubbell 2001). Whether and how the conceptual
frameworksforfoodwebs,mutualisticnetworks,interactionmodules,andhorizontal
communities can be truly merged—and not simply squeezed side by side into the

12 CHAPTER 2
Figure 2.1. Different ways of defining objects of study in community ecology for a hy-
pothetical terrestrial ecosystem. Each diagram represents the same system, but with the
direct object of study (whatever is inside the dashed-line box) defined in different ways.
Solid lines indicate interactions between species under consideration (omitted from (a)
for simplicity); solid-line boxes outside of the dashed-line box indicate all components
of the ecosystem that are externalized. Plant species 1 and 2 (“number plants”) belong to
a different functional group than species A and B (“letter plants”); species within such
functional groups (e.g., herbs vs. shrubs) are often lumped in food-web analyses (b).
Abiotic conditions
(e.g., temperature, pH)
Abiotic resources
(e.g., light, CO2, N)
(a) An ecological community sensu lato
Herbivore
1
Herbivore
2
Predator
Pollinator
1
Pollinator
2
Plant 1 Plant 2 Plant A Plant B
Decomposer
1
Pathogen 1 Pathogen 2
Decomposer
2
Decomposer
3
• Abiotic conditions
• Abiotic resources
• Pathogens
• Pollinators
• Decomposers
• Within-trophic level spp. dynamics
(b) A food web
Herbivores
Predator
Number
plants
Letter
plants
• Pathogens
• Other herbivores
• Pollinators
• Plants
• Decomposers
(d) A consumer-resource module
Herbivore
1
Predator

same package or combined in some specific contexts (there are lots of examples of
both)—remains to be seen. Before proceeding, I do wish to emphasize that this focus
does not marginalize the importance of trophic interactions or any other process or
variable treated as external to the object of study. Rather, as indicated previously, it
simply treats consumers or pathogens or mutualists as being outside the direct study
object of interest—a component of the biotic environment that potentially exerts
strong selection on the focal community and that might itself respond to changes in
this focal community (Fig. 2.1).
2.2. THE UBIQUITOUS ISSUE OF SCALE
In addition to studying very different sets of species, researchers also study
communities at many different spatial scales. Some definitions of an ecolog-
• Pathogens
• Predators
• Herbivores
• Decomposers
(c) A mutualistic network
Pollinator 1
Plant 1 Plant 2
Pollinator 2
Plant A Plant B
• Predators
• Pathogens
• Herbivores
• Pollinators
• Plants
(e) Horizontal communities
A decomposer community
Decomposer
1
Decomposer
2
Decomposer
3
• Predators
• Pathogens
• Herbivores
• Pollinators
• Decomposers
A plant community
Plant
1
Plant
2
Plant
A
Plant
B
Figure 2.1. Continued

14 CHAPTER 2
ical community (reviewed in Morin 2011) include species interactions as a
requirement, thus placing an upper limit on the spatial extent of a community.
I see no objective way to define such a spatial limit, so I prefer to leave species
interactions and any spatial restriction out of the definition of an ecological
community. Following Elton (1927), I consider the concept of a community
“a very elastic one, since we can use it to describe on the one hand the fauna
of equatorial forest, and on the other hand the fauna of a mouse’s cæcum.” As
such, the theory of ecological communities applies to analyses of community
properties (see Sec. 2.3) at any scale of space or time, which includes studies
not typically described under the banner of community ecology but, rather, as
biogeography, macroecology, or paleoecology.
Even with a spatially elastic definition of communities, one must remain
cognizant that processes and patterns observed at one scale may be quite dif-
ferent from those observed at another scale, and that a community may be
influenced by processes operating at many scales (Levin 1992). A tree in a
forest may experience competition only from its neighbors within a few meters,
it may be pollinated by insects traveling hundreds of meters, and its growth
might be affected by climatic fluctuations originating in altered water circula-
tion in the southern Pacific Ocean thousands of kilometers away. As will be-
come clear in subsequent chapters, some processes—e.g., negative frequency-
dependent selection—can result from highly localized species interactions
or from trade-offs involving dispersal at larger scales. The key point here is
that it is rarely if ever possible to define one “correct” scale for studying eco-
logical phenomena of interest (Levin 1992), especially if we are interested in
multiple interacting processes that might determine community structure and
dynamics.
Although the focal scale of observation can clearly vary continuously from
tiny study plots to entire continents, for sake of convenience community ecol-
ogists often recognize discrete scales, such as “local” (the smallest), “global”
(the largest), and “regional” (somewhere in between) (Ricklefs and Schluter
1993b, Leibold et al. 2004). For many studies, there is no need for scaling ter-
minology at all, in that areas of a narrow size range are being compared. These
areas might be highly variable in size from study to study—1- m2
plots, islands
of several square kilometers, or portions of a continent of hundreds of square
kilometers—but there is still no need to assign them a label. In other cases,
researchers refer to patterns or processes at multiple scales, most often those
occurring within the smallest focal area and those operating at larger scales.
In these cases, scaling terms are quite handy. Following convention in the liter-
ature, I refer to these as “local” and “regional,” respectively, while recognizing
that these terms do not have precise meanings beyond the fact that one is nested
within the other (see also Chap. 5). An ensemble of local communities is a
“metacommunity.”

2.3. THE PROPERTIES OF ECOLOGICAL COMMUNITIES THAT
WE WANT TO EXPLAIN AND PREDICT
For any focal community and spatial scale(s), ecologists have defined a variety
of different community-level properties of interest. Most generally, we are in-
terested in the number of species (species richness), the equitability of abun-
dances and the variety of traits among species (species/trait diversity), the iden-
tities and average trait values of species (species/trait composition), and the
relationships of these properties to site characteristics. This section describes
the quantification of these community properties, which we will refer to fre-
quently in subsequent chapters.
The basic quantitative description of a community is a vector of species
abundances, which we can call A. For a community of four species, with abun-
dances of a1
= 4, a2
= 300, a3
= 56, and a4
= 23, A = [4, 300, 56, 23]. The
abundances might be the number of adult trees of maple, beech, ash, and pine,
or of four species of woodpecker in a given site. This is equivalent to thinking
of the abundance of each of S species as a “state variable,” with the state of the
community being its position in the resulting S-dimensional space (Lewontin
1974). Most observational studies in community ecology include data from
multiple sites or local communities, in which case the raw data are represented
by a species × site matrix whose elements are species abundances (Fig. 2.2),
many of which are likely to be zeros. This matrix represents the “metacommu-
nity” and is made up of concatenated species abundance vectors, one for each
of j sites (A1
, A2
. . . Aj
). Armed with such data (and no additional data), we
can calculate what we might consider “first-order” community properties, as
follows.
First-Order Properties of Single Communities (Fig. 2.2)
Species richness: The number of species in the site (i.e., the number of
nonzero elements in A). When comparing sites in which different numbers
of individuals were observed, researchers often standardize species rich-
ness across sites by calculating the number of species observed in repeated
random samples of a given number of individuals in a given site, a proce-
dure called “rarefaction.” Unstandardized species richness is sometimes
called “species density” (Gotelli and Colwell 2001).
Species evenness/diversity: Any index calculated from the vector of species
abundances A in which, all else being equal, a more even distribution of
abundances across species leads to higher values. For example, a forest in
which total tree abundance is split 50:50 between two species has higher
evenness than a forest in which one of the two species abundances greatly
exceeds the other. Common indices are the Shannon-Weiner Index, Simp-
son’s Index, and various kinds of entropy calculations (Magurran and

16 CHAPTER 2
McGill 2010). These indices are typically based on the frequencies, freqi
= ai
/∑(ai
), of each species i.
Species composition: The vector of abundances (sometimes just recorded as
presence/absence) itself, unmodified (A), can be considered a multivariate
property of the community that one might wish to explain or predict.
Species abundance distribution: Regardless of which species has which
abundance, the distribution of these abundances (e.g., is it log-normal or
some other shape?) has been of great interest as a community property
(McGill et al. 2007).
First-Order Properties of Multiple Communities (i.e., a Metacommunity)
Beta diversity: Species composition is often studied by first calculating in-
dices that represent the degree of dissimilarity in species composition, or
beta diversity, between sites. To quantify beta diversity, a single number
can be calculated for the entire set of sites, or more commonly, an index is
calculated for each pairwise combination of sites. There is a very long list
Species 1 4 0 315 0
Species 2 300 250 0 223
Species 3 56 120 74 101
Species 4 23 18 0 0
Site 1 Site 2
1 community
Metacommunity
Species rank
1 2 3 4
For site 1:
Species richness = 4
Simpson’s evenness =
1/Σfreqi
2 = 1/Σ((4/383)2+(300/383)2+
(56/383)2+(23/383)2) = 1.57
Species abundance distribution
(shown as a rank-abundance plot):
Site 3 Site 4
Abundance
Abundance
300
250
200
150
100
50
0
Figure 2.2. The basic quantitative description of a metacommunity. The vector of spe-
cies’ abundances, A1
(gray-shaded rectangle), represents the multivariate “composition”
of the community in site 1, while the matrix represents the metacommunity of four sites.
Calculations of other first-order properties of the community at site 1 are shown to the
right. freqi
is the frequency of species i (its abundance divided by the sum of species’
abundances for that site).

of possible indices (Anderson et al. 2011). Without getting into quantita-
tive details, pairs of sites sharing similar abundance vectors (e.g., sites 1
and 2 in Fig. 2.2) show low beta diversity, while pairs with very different
abundance vectors (e.g., sites 1 and 3) show high beta diversity. For exam-
ple, beta diversity between a tropical and a temperate forest will be much
higher than beta diversity between two nearby plots in the temperate for-
est. This difference can be due both to turnover in the identities of species
in each site, as well as to differences in abundances of species present in
both sites.
Characterizations of pattern in ecological communities often draw on two
additional kinds of data. First, we can incorporate the characteristics (“traits”)
of each species into calculations of community properties for either single or
multiple communities (Weiher 2010; Fig. 2.3). For example, rather than asking
about how many species (species richness) and which species (species compo-
sition) live in different places, we can ask how the variance in body size among
species (trait diversity) or the average body size across species (trait composi-
tion) varies from place to place (McGill et al. 2006). Phylogenetic relationships
among species represent a special case of incorporating species-level charac-
teristics, with which we can calculate the degree of relatedness among species
as an index of “phylogenetic diversity” (Vellend et al. 2010).
Second, we can use site characteristics (e.g., their area, environment, or geo-
graphic isolation) to quantify relationships with first-order properties, and such
relationships then represent patterns in their own right requiring explanation.
Species 1 4 0 315 0
Species 2 300 250 0 223
Species 3 56 120 74 101
Species 4 23 18 0 0
Site 1 Site 2 Site 3 Site 4
Site characteristic 1 10 1 7 16
Site characteristic 2 0.01 0.4 0.2 0.5
Site characteristic 3 90 92 95 97
Site characteristic 4 12 0.1 0 5
0.2 320 0.5 20
0.6 298 0.1 16
0.9 412 0.1 26
1.3 300 0.2 21
Trait 1 Trait 2 Trait 3 Trait 4
Abundance
Figure 2.3. The three data tables needed to calculate various second-order commu-
nity properties, either incorporating species characteristics (traits) or site characteristics
(e.g., environmental variables). Traits are assumed to be fixed at the species level (i.e.,
not variable within species among sites).

18 CHAPTER 2
For example, we might calculate parameters of the statistical relationship be-
tween species richness and area or productivity and then seek to understand
how those parameters vary from case to case (Rosenzweig 1995). Although
not all site characteristics (e.g., temperature, geographic isolation, presence of
a predator) fall readily under the heading “environmental variable,” for sim-
plicity I will often use the term “environment” to refer them as a group. Given
the incorporation of data that go beyond the basic species × site matrix, we can
think of the patterns just described as “second-order” community properties.
Second-Order Community Properties Incorporating Species Characteristics
Trait diversity: Several indices quantify the degree of within-community var-
iation among species in trait values, for either single or multiple traits.
Traits are often described as “functional” in the sense that they have some
impact on fitness (Violle et al. 2007), so such indices are frequently de-
scribed as reflecting “functional diversity” (Laliberté and Legendre 2010,
Weiher 2010).
Trait composition: The community-level average value of a given trait is es-
sentially one way to quantify community composition (Shipley 2010).
Second-Order Community Properties Incorporating Site Characteristics
Diversity-environment relationships: The relationship between local diver-
sity (any first- or second-order metric) and a particular site characteristic.
Frequently studied site characteristics include the area over which a survey
was done (species-area relationships) and any number of “environmental”
variables such as productivity, disturbance history, elevation, latitude, pH,
geographic isolation, or soil moisture availability (Rosenzweig 1995).
Composition-environment relationships: The strength and nature of relation-
ships between species composition (including trait or phylogenetic com-
position) and any site characteristics of interest. Such analyses can be
implemented in many different ways (Legendre and Legendre 2012), in-
cluding analyses that aim to predict pairwise site-to-site indices of beta
diversity using pairwise differences among sites in certain characteristics
(e.g., the geographic distance between sites). These are discussed further
in Chapter 8.
It is important to emphasize that there is an extremely large number of ways
of calculating each type of community property, and an even larger number
of ways of analyzing those properties. These have been described in detail
elsewhere (Magurran and McGill 2010, Anderson et al. 2011, Legendre and
Legendre 2012). I have presented here the basic set of conceptually distinct
patterns one might quantify in communities.

To summarize, the theory of ecological communities applies most clearly to
horizontal ecological communities, and it applies to any scale of space or time.
Community ecologists describe patterns in a variety of first- and second-order
community properties, and in subsequent chapters I explore how all these prop-
erties can be understood as the outcome of four high-level processes: selection,
drift, speciation, and dispersal.

C H A P T E R 3
A Brief History of Ideas in Community Ecology
Ideas do not arise in a vacuum. This book was inspired both by a perceived
“mess” of loosely related models and patterns in community ecology (Mc-
Intosh 1980, Lawton 1999), as well as some conceptual developments in ecol-
ogy and evolutionary biology that pointed the way to what I consider a very
general theory that can help contain the mess (Mayr 1982, Ricklefs 1987, Hub-
bell 2001, Leibold et al. 2004). In addition to my broad goal in this chapter
of putting the theory of ecological communities in historical context, my aim
is to communicate both how community ecology came to be perceived as a
mess and where the building blocks of my own theory originated. I do so by
providing a brief history of the research traditions in ecology most relevant to
horizontal communities. Along the way, if you start to feel confused about how
all the historical pieces of community ecology fit together, that is indeed one of
the points I wish to make, and is a problem the rest of this book aims to solve.
Experts familiar with the history of community ecology may wish to skip to
Sections 3.4 and 3.5, which present a synthetic, forward-looking perspective.
The history of community ecology does not involve a linear sequence of
events. For any current research area (e.g., metacommunities or trait-based
community analyses), one can identify numerous intellectual strands extending
backward in time to different origins. Likewise, most foundational ideas (e.g.,
the competitive exclusion principle or the individualistic concept) have had an
influence on many different current topics of research (McIntosh 1985, Worster
1994, Kingsland 1995, Cooper 2003). Therefore, any one person’s historical
account will differ from that of others. In addition, because the basic subject
matter of ecology involves commonplace phenomena such as the distributions

IDEAS IN COMMUNITY ECOLOGY 21
and behaviors of plants and animals, core ideas in ecology can be traced back
thousands of years (Egerton 2012). Many nineteenth-century scientists and nat-
ural historians, such asAlexander von Humboldt (1769–1859), Charles Darwin
(1809–1882), and Eugenius Warming (1841–1924), could easily be considered
community ecologists (among other things) by modern standards. Nonetheless,
to understand how the different pieces of present-day community ecology fit
together, we can stick largely with more recent conceptual developments.
The brief historical sketches I present here extend back no further than a cen-
tury or so. I have not aimed to provide a comprehensive historical account nor
to mention all important contributions, as several excellent historical treatments
of ecology collectively do this (McIntosh 1985, Worster 1994, Kingsland 1995,
Cooper 2003, Egerton 2012). With an eye to covering the conceptual ground
necessary to understanding modern-day “horizontal” community ecology spe-
cifically (see Fig. 2.1), I focus on the development of three themes: (i) making
sense of community patterns (Sec. 3.1), (ii) generating and testing predictions
from simplified mathematical models (Sec. 3.2), and (iii) examining the im-
portance of large-scale processes (Sec. 3.3). Section 3.4 focuses on a series of
debates and waves of interest in various topics in community ecology over the
past 50 or so years, from which the building blocks of the theory of ecological
communities emerged. I focus this chapter largely on conceptual approaches
and developments, with minimal empirical content. Empirical studies are the
subject of Chapters 7–10.
3.1. MAKING SENSE OF COMMUNITY PATTERNS
OBSERVED IN THE FIELD
For well over a century, field biologists have been characterizing patterns in
ecological communities and trying to draw theoretical inferences from the re-
sulting data. One of the earliest theoretical debates in ecology concerned the
question of whether communities in nature could be recognized as discrete en-
tities. Frederic Clements (1916), an American plant ecologist, said yes. Clem-
ents held that a community was an integrated entity within which species were
as interdependent as organs in a human body. According to this point of view,
change in species composition along an environmental gradient is not gradual
but, rather, abrupt (Fig. 3.1a). Because of this strong interdependence among
species within a community, moving up a mountainside of mature forest, for
example, one could find oneself in community type 1 or 2 but rarely if ever in
a transitional community type (Fig. 3.1a).
Clements’s ideas aligned nicely with the tradition of vegetation classifica-
tion, which was a major focus of botanists’ efforts in Europe in the early twen-
tieth century, as typified by the “Zurich-Montpellier” approach pioneered by
Josias Braun-Blanquet and colleagues (Braun-Blanquet 1932). The basic data

22 CHAPTER 3
involved plant community surveys, with subsequent efforts aimed at organizing
study plots into a hierarchical vegetation classification scheme (each plot was
assigned to a particular vegetation “type”), thus implicitly assuming that eco-
logical communities are discrete entities.
Opposition to Clements’s view of an ecological community as a “superor-
ganism” is most often associated with Henry Gleason, who argued that each
species responded in a unique way to environmental conditions (Fig. 3.1b).
Community
type 1
Community
type 2
(a) Clements’s
superorganism hypothesis
No discrete communities
(b) Gleason’s
individualistic hypothesis
(c) Data from
Mont Mégantic, Québec
Environmental gradient
2.0
1.5
1.0
0.5
sugar maple
paper birch
yellow birch
red spruce
Environmental gradient
Abundance
Elevation (m)
550 650 750 850 950 1050
log(%
cover
+
1)
Figure 3.1. (a, b) Two competing hypotheses regarding species distributions along en-
vironmental gradients, and thus the organization of species into communities (i.e., par-
ticular points along the x-axis). (c) Locally weighted scatter plot smoothing (LOESS)
curves (tension = 0.7) for the five most abundant tree species in 48 vegetation plots
along an elevational gradient at Mont Mégantic, Québec (data from Marcotte and
Grandtner 1974). These data illustrate gradual change in community composition along
the gradient, thus supporting hypothesis (b).

According to this point of view, the set of species one finds in a given place
results more from species-specific or “individualistic” responses to various en-
vironmental factors than from strong interdependence among species (Gleason
1926). Support for this supposition came later from data showing gradual varia-
tion in community composition along environmental gradients (e.g., elevation)
rather than abrupt transitions from one community type to the next (Whittaker
1956, Curtis 1959; Fig. 3.1c). This reality forced ecologists to operationally
define communities as the set of species in sometimes arbitrary units of space,
as I have done in this book (see Chap. 2).
Until the 1950s, analyses of community survey data were largely qualitative.
Quantitative data were presented in tabular form or in graphs of how species
abundances changed along particular gradients (e.g., Fig. 3.1), but conclusions
were drawn from qualitative inspection of such tables and graphs (e.g., Whit-
taker 1956). A clear need for quantitative, multivariate methods of analysis was
apparent, and this need was filled by methods developed under the heading
of “ordination” (Bray and Curtis 1957). Multivariate ordination aims to place
survey plots “in order” based on their multivariate species composition. Such
methods begin by considering the abundance of each species as a separate var-
iable measured at each site, such that the “response” of interest is inherently
multivariate (i.e., the vector of species abundances described in Chap. 2). Be-
cause many species pairs show correlated distribution patterns (positive or neg-
ative), ordination methods are typically able to identify and extract a relatively
small and manageable number of dimensions along which most variation in
community composition occurs (Legendre and Legendre 2012). For example,
if we conduct an ordination of only the species × site data used to create Figure
3.1c (i.e., without incorporating any information on elevation), the first axis of
an ordination analysis would correlate strongly with elevation, given that so
many of the species show correlated distribution patterns along this axis. Such
methods allow one to ask—quantitatively— which environmental or spatial
variables best predict site-to-site variation in community composition (Legen-
dre and Legendre 2012)?
To the extent that different community theories make different predictions
about the explanatory power of different variables, the results of multivariate
community analyses can in principle allow empirical tests (see Chaps. 8–9).
As a relatively recent example, neutral theories (described in Sec. 3.3) predict
no direct role of environmental variables (e.g., elevation or pH) in explaining
community composition but an important role of spatial proximity among sites.
The development and application of new multivariate methods of community
analysis has continued unabated for the last 50+ years and characterizes a
major thrust of current research (Anderson et al. 2011, Legendre and Legendre
2012, Warton et al. 2015).
As described in Chapter 2, ecologists have documented many other
community-level patterns as well, such as species-area relationships, relative

24 CHAPTER 3
abundance distributions, and trait distributions (e.g., body size), and subse-
quently have sought explanations for such patterns. Many such explanations
derive from mathematical models of one sort or another, as described in the
next two sections.
3.2. SIMPLIFIED MATHEMATICAL MODELS
OF INTERACTING SPECIES
One cannot overstate the massive influence of population modeling in ecology.
This is one case in which a major research tradition can be traced back to some
singular contributions (Kingsland 1995), in particular the models of interacting
species developed independently by Alfred Lotka and Vito Volterra (see also
Nicholson and Bailey 1935). Models of this nature can be used to try to make
sense of community patterns already observed and to generate new predictions
for how community dynamics should proceed under different conditions. The
simulation models presented in Chapter 6 fall squarely within this tradition. To
understand where these models, and their hundreds of descendants, come from,
we must start with simple models of single populations.
Population growth is a multiplicative process. When a single bacterium
splits in two, the population has doubled, and when these two cells divide, the
population has doubled again, to produce a total of four individuals. If Nt
is the
population size at time t, and cell division happens in discrete time steps, then
N1
= N0
× 2, N2
= N1
× 2 = N0
× 2 × 2, and so on. For any “reproductive factor”
R, Nt+1
= Nt
× R (Otto and Day 2011). Because the population grows multi-
plicatively without limit according to this equation (Fig. 3.2a), it is called ex-
ponential population growth. To make the transition to more complex models
smoother, we can define R = 1 + r, in which r is the intrinsic rate of population
growth. Otto and Day (2011) use the symbol rd
to distinguish this definition of
r for discrete-time models from that used in continuous-time models (r = log
R), but here I use just r to simplify the notation. If r > 0, the population grows,
and vice versa. So, Nt+1
= Nt
(1 + r), and
Nt+1
= Nt
+ Nt
r.
Of course, populations cannot grow without limit. Although many factors
can limit population growth, for a single species the most obvious possibility
is the depletion of resources as more and more individuals consume from the
same limited supply. In this case, resources should be very abundant when a
species is at low density (i.e., there are no organisms to deplete the resource),
and so the population can grow exponentially. As the population grows, re-
sources will be depleted, and so population growth should slow. If we define
a maximum population size that can be sustained in a given place as K, the
“carrying capacity,” then population growth should decrease as the population

size approaches K. Nt
/K expresses how close the population is to K, so 1 – Nt
/K
expresses how far the population is from K. We can express the realized popu-
lation growth as r(1 – Nt
/K). If Nt
= K, the realized population growth is zero,
and as Nt
approaches zero, the realized population growth approaches r. This
scenario is captured by the logistic equation for population growth (Fig. 3.2a):
Nt+1
= Nt
+ Nt
r(1 – Nt
/K).
The logistic equation represents a minor modification of the exponential-
growth equation via the addition of reduced population growth as the popu-
lation itself gets large and depletes resources. But of course, resources can be
depleted (or, in principle, added) by other species. With the addition of a sec-
ond species, we now need subscripts 1 and 2 to keep track of species-specific
variables and parameters (e.g., N1
and N2
). A simple way to model competition
is to express the influence of each individual of species 2 on species 1 as some
proportion of the influence species 1 has on itself. We call this parameter the
competition coefficient, α12
(the effect on species 1 of species 2). If an individ-
ual of species 2 depletes the resources needed by species 1 at half the rate that
species 1 depletes its own resources, α12
= 0.5. So, if there are N2
individuals of
species 2 in the community, they have the equivalent effect on species 1 as α12
×
N2
= 0.5 × N2
individuals of species 1. With this assumption, we can now account
for resource depletion by competing species in models of the two species pop-
ulation dynamics. Things look more complicated because we have to introduce
all the subscripts, but it is really just one small addition to the logistic equation:
N1(t+1)
= N1(t)
+ N1(t)
r1
(1 – N1(t)
/K1
– α12
N2(t)
/K1
);
N2(t+1)
= N2(t)
+ N2(t)
r2
(1 – N2(t)
/K2
– α21
N1(t)
/K2
).
To model more species, we add an equation for each species and include an
additional factor αij
Nj
for the effect of each species j on species i.
In Chapter 6 we will explore theoretical dynamics in some models of this na-
ture. For now, suffice it to say that the outcome of competition between species
1 and 2 depends largely on the relative values of the K’s and the αij
’s. All else
being equal, stable species coexistence is promoted when intraspecific compe-
tition is stronger than interspecific competition (i.e., α12
× α21
< 1) and when the
carrying capacities, K1
and K2
, are not too different (Fig. 3.2b, c). Basic mathe-
matical models of this type for interacting species have been a part of ecology
for roughly 100 years, and an enormous number of minor (and perhaps not so
minor) modifications have been introduced since then.
3.2.1. The Enduring Influence of Population Modeling in
Theoretical and Empirical Community Ecology
A major wave of enthusiasm for mathematical models in ecology swelled
in the 1960s and 1970s, largely via the contributions of Robert MacArthur

26 CHAPTER 3
and colleagues, including MacArthur’s PhD director, G. Evelyn Hutchinson
(Kingsland 1995). Many models of competing species include an explicit ac-
counting of the dynamics of resources (e.g., equations representing the dynam-
ics of the limiting nutrients for which plants compete), the results of which
help specify the types of trade-offs among species that might promote stable
coexistence. For example, if each of two species is (i) limited by a different
(a) Single-species exponential
and logistic population growth
Logistic
growth
Exponential
growth
60
40
50
30
20
10
Time
0 10 20 30 40
(b) Two-species Lotka-Volterra
competition: stable coexistence
Species 1
Species 1
Species 2
20
10
15
5
Time
0 50 100 150
Population
size
(N)
(c) Two-species Lotka-Volterra
competition: competitive
exclusion
40
30
20
10
0
0
0
Time
0 50 100 150
Population
size
(N)
Species 2
Figure 3.2. Population dynamics of (a) single species under exponential and logistic
population growth, and (b, c) two competing species under Lotka-Volterra competition.
In all panels, r = r1
= r2
= 0.2 (see the text for equations). In (b) and (c), α21
= 0.9, and α12
= 0.8, such that species 1 has a stronger competitive effect on species 2 than the reverse.
For carrying capacities, K = 30 for the logistic growth model in (a), for both species in
(b), and for species 1 in (c). In (c), K2
= 40, thus giving an advantage to species 2, which
overcomes its weaker competitive effect.

resource and (ii) takes up the resource by which it is most limited faster than
the other species, stable coexistence is possible given certain rates of supply of
the two resources (Tilman 1982).
Ultimately, it was realized that regardless of the details of a particular model
or natural community, the long-term outcome of competition among species
depends on just two key factors (Chesson 2000b). This result can be illustrated
by first recognizing that stable species coexistence depends fundamentally
on each species having a tendency to increase when its abundance gets very
low. Otherwise, we should see competitive exclusion. Even from the original
Lotka-Volterra competition model, we can learn that coexistence depends on
two key interacting factors: (i) intraspecific competition must be stronger than
interspecific competition (α12
× α21
< 1), and (ii) differences among species in
their average performance in a given place (represented by K) must be suffi-
ciently small so as not to overwhelm factor (i). These are essentially two ways
in which species can differ from each other, and in what has been called “mod-
ern coexistence theory” (HilleRisLambers et al. 2012), these have been dubbed
“niche differences” and “fitness differences,” respectively (Chesson 2000b). In
mathematical terms, the rate of population growth when rare, rrare
, is a function of
these two kinds of difference as well as a scaling coefficient (s) that allows them
to be expressed in units of population growth rate (MacDougall et al. 2009):
rrare
= s(fitness difference + niche difference).
For simplicity, I have so far described models that focus largely on commu-
nity dynamics in single, closed communities, where the environment is homog-
enous in space and time. Many other models have been developed that relax
these assumptions—for example, involving environmental heterogeneity in
space or time. The consequences of different amounts of dispersal between two
or more local communities have been explored in models under the umbrella of
what we now call “metacommunity ecology” (Leibold et al. 2004). These types
of models are treated in greater detail in Chapters 5 and 6.
Mathematical models— as well as many verbal models extending their logic
to specific situations— have motivated empirical studies of various kinds (see
Chaps. 8–9). Gause (1934) pioneered the use of lab microcosms containing mi-
crobes or very small bodied species (e.g., paramecia, yeast) to first estimate the
parameters of a particular model and then to test its predictions in independent
trials (see also Vandermeer 1969, Neill 1974). Such experiments led to Gause’s
“competitive exclusion principle,” which essentially states that, given the in-
evitability of some fitness differences among species (sensu Chesson 2000b),
coexistence of two species competing for the same resource is not possible
because there is no scope for niche differentiation. Extending this principle
to large numbers of species that seemingly all compete for the same few re-
sources, Hutchinson (1961) used observations of phytoplankton in lakes to de-
clare the “paradox of the plankton.”

28 CHAPTER 3
Many studies have aimed to characterize the differences among species (e.g.,
associations with different abiotic environmental conditions, or differential re-
source partitioning) that might allow them to coexist (Siepielski and McPeek
2010). Many other studies have searched for patterns in observational data on
species distributions or community composition that are expected under strong
competition—the central process of interest in the 1960s and 1970s (Diamond
1975, Weiher and Keddy 2001). One such pattern is a “checkerboard” formed
by the distributions of two species, in which one or the other occurs often in
any given site, but rarely the two together (Diamond 1975). Still other studies
have experimentally manipulated particular factors of interest (e.g., the density
or presence of other species, resource supply, dispersal) and tested whether the
results reveal strong species interactions of one kind or another (e.g., competi-
tion, predation, or facilitation) or changes in community composition predicted
by theoretical models (Hairston 1989). All these lines of research are alive and
well in contemporary community ecology (Morin 2011, Mittelbach 2012).
3.3. LARGE-SCALE PATTERNS AND PROCESSES
More often than not, ecological patterns, and the importance of different pro-
cesses in explaining them, depend on the spatial scale of observation (Levin
1992). For example, at a small spatial scale (e.g., comparing individual ponds)
maximum species diversity might be found at intermediate productivity,
whereas at a larger scale (e.g., comparing watersheds) species diversity might
increase steadily with increasing productivity (Chase and Leibold 2002). Many
definitions of an ecological community include the criterion that the species
within a community interact with one another (Strong et al. 1984, Morin 2011),
which consequently places an upper limit on the spatial extent of a community.
Defining where to place such a limit is rather difficult, to put it mildly (see
also Chapter 2), but it’s fair to say that for most kinds of organisms the scale
would likely be measured in square centimeters (microbes), square meters
(herbaceous plants), or hectares (small mammals) rather than square kilome-
ters. However, the core questions of community ecology— for example, why
do we find different types and numbers of species in different places/times?—
are literally identical to questions asked by scientists working at larger spatial
scales (e.g., among biogeographic regions). Historically, such scientists might
have called themselves biogeographers, whereas today they might equally call
themselves macroecologists, or just ecologists. I would call them community
ecologists as well.
Explanations for large-scale community patterns (e.g., comparing different
continents or biomes) do involve consideration of some processes typically
assumed to be of negligible importance at smaller scales. For example, the ge-
ologic and evolutionary histories of a region play major and perhaps dominant

roles in shaping regional biotas (Ricklefs and Schluter 1993a). However, such
“regional biotas” have repeatedly come into contact and subsequently mixed,
thus presenting an opportunity for “typical” community-level processes such
as competition to play an important role in determining large-scale community
patterns (Vermeij 2005, Tilman 2011). In addition, sharply contrasting biomes
containing species with (semi)independent evolutionary histories can often
occur in very close proximity (e.g., temperate forest, boreal forest, and tundra
along one mountainside). Finally, the types and numbers of species contained
in a regional biota or “species pool” might have an important influence on ex-
actly how different processes are manifested as local-scale patterns (Ricklefs and
Schluter 1993a), such as the relationship between species diversity and a particu-
lar environmental gradient (Taylor et al. 1990). All these observations and ideas
have intellectual roots going back 100 years or more. However, their integration
with small-scale studies in community ecology is comparatively more recent.
Processes thought to act at relatively large spatial scales have been repre-
sented in theoretical models in various ways. Quite in contrast with his models
of locally interacting species, Robert MacArthur along with E. O. Wilson de-
veloped the “theory of island biogeography” (MacArthur and Wilson 1967),
which posited that local species composition on an island was in constant flux,
with species diversity determined by a balance between immigration from a
continental mainland and local extinction. The resulting model predicted—and
therefore helped make sense of—patterns showing reduced species diversity on
smaller and more isolated islands (Fig. 3.3).
Interestingly, the key features of the island biogeography model make no
important distinction between different identities of species (Hubbell 2001).
From a pool of species on a hypothetical mainland, individuals arrive at a given
rate regardless of species, and the rate of colonization (i.e., the arrival of a
Equilibrium
species
richness
Extinction
Colonization
Local species richness
Rate
Small islands
Large islands
Connected
islands
Isolated
islands
Rate
Figure 3.3. The essential features of MacArthur and Wilson’s (1967) model of island
biogeography, illustrating why island area and connectivity/isolation influence species
richness.

30 CHAPTER 3
new species) declines with increasing local species richness because fewer and
fewer of the new arrivals will represent species not already present. Larger is-
lands can harbor larger populations, which, again regardless of species identity,
have a lower chance of going locally extinct. Hubbell (2001) recognized this as
one special case of a more general neutral theory, meaning a theory assuming
no demographic differences among individuals of different species. He added
speciation and an individual-level birth-death process to generate predictions
of the shape of species-abundance distributions, species-area relationships, and
the distance decay of community similarity (i.e., the decreasing similarity in
the composition of communities located increasingly farther apart) at a wide
range of spatial scales.
The striking match between the predictions of Hubbell’s neutral theory and
the empirical patterns just described caused a major controversy and a flurry
of research activity in the 2000s, mostly aimed at documenting patterns not
predicted by neutral theory (McGill 2003b, Dornelas et al. 2006, Rosindell et
al. 2012). Many of these patterns (e.g., strong correspondence between species
composition and environmental variables) were already well known. I think the
longer-lasting legacy of neutral theory has been a sharp reminder that processes
other than those necessarily involving species differences—specifically, drift,
dispersal, and speciation—can play important roles in shaping many patterns
of interest in ecological communities, regardless of whether selective processes
are important in influencing some of the same patterns or even solely responsi-
ble for creating other patterns.
Speciation has long been recognized as a key factor in determining the num-
ber of species across large areas, given that it is one of only two sources of
species “input” into a given area (to be discussed further in Chapter 5). In aim-
ing to explain the latitudinal gradient in species diversity, MacArthur (1969)
sketched out a model quite similar to the island biogeography model, except
with a balance between immigration + speciation versus extinction, rather than
only immigration versus extinction (see also Rosenzweig 1975). Indeed, it is
a truism that if one area has more species than another, the balance of inputs
(speciation and immigration) versus outputs (extinction) must be different.
A major push for wider recognition of the importance of regional species
pools (created by speciation, immigration, and extinction) in determining the
nature of local-scale community patterns came from Robert Ricklefs and col-
leagues in the 1980s and 90s (Ricklefs 1987, Cornell and Lawton 1992, Rick-
lefs and Schluter 1993a). I illustrate the basic thrust of this line of research
with two examples in which predictions of hypotheses based on the dominance
of local-scale species interactions contrast with predictions based on the hy-
pothesis that properties of the regional species pool determine local patterns.
First, if local species diversity is limited by competition (i.e., communities are
“saturated” with species), then the number of species in small areas should
not depend on the number of species in the regional pool, unless the regional

species pool is exceptionally depauperate. If, however, local competition is
insufficiently strong to put a hard cap on the number of species, local richness
should increase linearly with regional richness (Cornell and Lawton 1992). The
basis of this prediction can be understood as a twist on the island biogeography
model (Fox and Srivastava 2006) (Fig. 3.4a). Patterns in empirical data vary
widely among systems, spanning the full range of possibilities between the two
hypotheses in Figure 3.4b (see Chap. 10).
The second example pertains to explaining the shape of the relationship be-
tween species diversity and a given environmental variable (e.g., productivity).
For the hump-shaped relationship often observed between species richness and
productivity, a “local” hypothesis might posit that severe environmental condi-
tions prohibit all but a few species from persisting at low productivity, severe
competition reduces diversity at high productivity, and both types of species
can coexist at intermediate productivity (Grime 1973). In contrast, a “regional”
hypothesis might posit that competition plays no direct role but that interme-
diate productivity conditions have predominated over both space and time
throughout the evolutionary history of the regional biota, such that more spe-
cies have evolved to perform best under these conditions (Taylor et al. 1990).
Thus, the effective size of the regional species pool varies among habitats with
different productivities and consequently determines local diversity patterns.
Testing these competing predictions with just one pattern is impossible, but if
the shape of such relationships varies among regions, then according to the re-
gional or “species-pool” hypothesis, we should be able to predict the direction
of diversity-environment relationships based on knowledge of conditions that
Extinction
Colonization
Low
diversity
region
High diversity region
(e.g., high speciation)
Rate
Regional species richness
Regional-
determines-
local
Local saturation
Local
species
richness
(a) Underpinnings of the regional-
determines-local hypothesis
(b) Predictions of the regional-
determines-local and local
saturation hypotheses
Figure 3.4. Application of the island biogeography model to predicting the effect of
regional diversity on local diversity (a), and a graphical depiction of competing predic-
tions of regional versus local hypotheses. In (b) it is assumed that saturation, if present,
would be manifested only above some minimal level of richness.

32 CHAPTER 3
have predominated over large spatial/temporal scales (Pärtel et al. 1996, Zobel
1997, Pärtel 2002) (Fig. 3.5). Very few studies have directly tested this predic-
tion, but they do support the species-pool hypothesis (see Chap. 10).
3.4. A SEQUENCE OF ACTIONS AND REACTIONS OVER THE
LAST 50 YEARS OF COMMUNITY ECOLOGY
I think that the last 50 years of community ecology can be understood largely as
a sequence of overlapping waves of enthusiasm for a particular phenomenon,
process, or approach whose importance was perceived as underappreciated or
understudied at a given moment in time (Fig. 3.6; see also McIntosh 1987,
Region 1 Region 2
Longitude
Latitude
Latitude
Longitude
pH
Local
species
richness
pH
Local
species
richness
Figure 3.5. Illustration of the “species-pool hypothesis” to explain the shape of diversity-
environment relationships. In region 1, high-pH conditions predominate in the region
(top panel), so a positive diversity-pH relationship is found, and vice versa for region 2.

Kingsland 1995). Many such waves were marked by the publication of one or
more books that now serve as sign posts to this history (Cody and Diamond
1975, Tilman 1982, Strong et al. 1984, Diamond and Case 1986, Ricklefs and
Schluter 1993a, Hubbell 2001, Chase and Leibold 2003, Holyoak et al. 2005).
Of the three research traditions discussed in Sections 3.1–3.3, two of them
gained a major thrust of momentum via the work of Robert MacArthur and col-
leagues in the 1960s. These colleagues included Richard Lewontin, E. O. Wilson,
and Richard Levins, and collectively this group has been called the “Marlboro
Circle,” after Marlboro, Vermont, where they met for discussions at Mac-
Arthur’s lakeside home (Odenbaugh 2013). In many ways, the other major
research tradition described earlier (making sense of observational patterns)
has also been largely repurposed for testing theoretical ideas that were formu-
lated or at least clarified in this same period. The fact that dueling hypotheses
(e.g., local vs. regional controls on community patterns) can both trace their
origins to the same author (Fig. 3.6) has been dubbed “MacArthur’s paradox”
(Schoener 1983b, Loreau and Mouquet 1999). The 1960s thus serves as a good
starting point for tracing the more recent origins of present-day topics of active
research in community ecology.
The MacArthur School (Marlboro Circle)
:
n
o
i
t
i
t
e
p
m
o
c
f
o
s
l
e
d
o
m
e
l
p
m
i
S
y
h
p
a
r
g
o
e
g
o
i
B
d
n
a
l
s
I
compare equilibrium to data – draw inferences
Major problems inferring
process from pattern
Most of the world is not at
equilibrium most of the time
Patch dynamics
and disequilibrium
Better“null”models
for community
assembly studies
Spatial
ecology
Neutral
theory
Niche-neutral
reconciliation
Metacommunity
ecology
Back to historical and
regional perspectives
Macroecology
Experiments ignore large-scale
processes and give
experiments
Figure 3.6. Major research programs, methods, theories, or conceptual frameworks
(gray boxes) in community ecology over the last 50 years, linked by perceived weak-
nesses in a particular reigning paradigm (white boxes).

34 CHAPTER 3
Models based on interspecific competition as a dominant structuring force
in ecological communities constituted the first wave (Cody and Diamond
1975). A great hope was that such models would provide the basis for a general
and universally applicable theory of ecology (Diamond and Case 1986). This
was not to be (McIntosh 1987). First, many communities are structured more
strongly by predation than competition, and major criticism arose charging that
any and every bit of data gathered was being interpreted as support for the
competition-centric worldview without a rigorous consideration of alternative
hypotheses (Strong et al. 1984). A second criticism was that the real world
should not be expected to look like the equilibrium solution to a simple model,
because the real world is rarely at equilibrium or simple (Pickett and White
1985, Huston 1994). These two criticisms led to the initiation or at least revival
of at least three lines of research (the next waves in the sequence): (i) the use
of null models to explicitly evaluate the likelihood that certain patterns might
arise in the absence of competition (Gotelli and Graves 1996), (ii) a focus on
perturbations from equilibrium and “patch dynamics” via disturbance (Pickett
and White 1985), and (iii) the use of field experiments to test for the mecha-
nisms underlying community patterns (Hairston 1989).
Ecologists active in the 1980s have recounted to me that it was difficult to
get a paper accepted in a good journal if the study wasn’t experimental. Field
experiments are critical tools for testing process-based hypotheses. However,
they come with severe logistic constraints in that all but a few are done at very
small spatial scales (e.g., square-meter cages on a rocky shore, or plots in a
grassland), and experiments are either logistically impossible or unethical in
many systems (Brown 1995, Maurer 1999). Recognition of the limitations of
the intense focus on processes at a local scale itself led to a new research wave,
already described previously: the integration of regional processes into our
understanding of communities, even at a local scale (Ricklefs 1987, Ricklefs
and Schluter 1993a). One of the key processes emphasized by proponents of
regional-scale phenomena is dispersal. Dispersal was already a key feature of
island biogeography theory, which forces one to think explicitly about spatial
scale. In the 1990s, space had been described as the “next frontier” in ecology
(Kareiva 1994), and “spatial ecology” (Tilman and Kareiva 1997) was a buzz-
word for a time, now manifested—at the community level—as metacommu-
nity ecology (Leibold et al. 2004, Holyoak et al. 2005).
The theory of island biogeography (MacArthur and Wilson 1967) has had a
major influence in ecology and perhaps even more so in conservation biology as
a basis for predicting extinction with habitat loss and in the design of nature re-
serves (Losos and Ricklefs 2009). The idea that landscapes are patchy (often with
island-like habitat remnants), with frequent local extinctions and colonizations,
became a center piece of research under the heading “patch dynamics” (Pickett
and White 1985). As described earlier, one of the more controversial theories put
forward during the last 30 years in ecology—Hubbell’s (2001) neutral theory—

was inspired in part by island biogeography theory. Neutral theory is considered
one pillar of the metacommunity framework, and a major focus of the past 15
years or so has been an effort to reconcile the success of neutral theory in pre-
dicting some patterns in nature with the fact that one of its assumptions (demo-
graphic equivalence of individuals of different species) is clearly false (Gewin
2006, Gravel et al. 2006, Holyoak and Loreau 2006, Leibold and McPeek 2006).
3.5. PROLIFERATION AND DISTILLATION OF THEORETICAL
IDEAS IN COMMUNITY ECOLOGY
With the waxing and waning of various models, conceptual ideas, buzzwords,
methods, and philosophies in community ecology over the past century, a stu-
dent could be forgiven for finding difficulty in seeing any kind of overarching
structure into which everything fits. Each new perspective or theory has typi-
cally emphasized one or a few processes—not necessarily to the exclusion of
others, but at least with a focus on a particular subset: neutral theory empha-
sizes everything except selection, niche theory focuses on selection, metacom-
munity theory emphasizes dispersal, and so on. The various waves of interest
in different topics during the time that I have been a student of community
ecology ultimately laid bare (to me) the fact that all the processes of interest
can be reduced to four analogues of the processes in population genetics, which
students have no trouble easily seeing as the overarching conceptual structure
into which everything in that discipline can fit.
In communities, the term selection has been used only sporadically to de-
scribe a process acting among individuals of different species (Loreau and
Hector 2001, Norberg et al. 2001, Fox et al. 2010, Shipley 2010), but all the
deterministic outcomes of ecological models involving differences between
species, from Lotka-Volterra to the present, are essentially models of selection
in communities (Vellend 2010). So, selection has always been a conceptual
focus of community ecology. The potential influence of community drift, via
demographic stochasticity, has been recognized for a long time, but it took
root in the field as a whole only after Hubbell (2001) stirred the pot with his
neutral theory. Likewise, dispersal has featured in prominent ecological models
for many decades, but development of the metacommunity concept (Leibold
et al. 2004) has served as a reminder of its central place as a distinct process
influencing communities. Finally, the importance of considering the formation
of regional species pools when studying communities at any scale (Ricklefs
and Schluter 1993a), as well as the emergency of macroecology (Brown 1995),
added speciation to the mix of distinct processes that can influence ecological
communities. With these four processes in hand, the smorgasbord of theory in
community ecology can be reined in and understood as many combinations of
a few key ingredients.

P a r t I I
THE THEORY OF ECOLOGICAL
COMMUNITIES

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I can at any time trump up a story of your attempting to corrupt the
turnkeys, and be sure, when I do, I will not want for proofs. That
will cover any thing I can do to annoy you, and answer any
accusation you can make against me. Do you think that the word of
a jailor will not be taken, before that of the murderer he has in
custody?”
“I can bring your own servants as witnesses, three of whom
assaulted me last night.”
“Dunce, do you think I trusted them with my secret? They have
nothing to tell, and apprehend nothing but a plot between you and
my black, who has been put into the penitentiary for his offence. He
is my only confident; and I trust him, because his stupidity answers
to me for his faith.”
“Suppose I were to double the bribe for which you sold me my
liberty, what security should I have that you would abide by your
bargain?”
“Oh, if you were to do that, it would alter the case.”
“Might you not then detain the money, and defy me, as you have
done now?”
“Suppose that a thing which might happen: can you help yourself?
can you do better?”
I saw there was no remedy, and I was constrained to allow the
success of this twofold perfidy. It was with an ill grace, and an
attempt at sullenness and indifference, that the jailor accepted my
proposal. The second thousand however had irresistible charms;
and, in spite of himself, the sensation that made his heart dance,
relaxed his muscles, and played about his mouth. He was puzzled
what to think of me. The facility with which I produced the sums he
demanded, with less apparent effort than they might have come
from a duke or a sovereign prince, startled and staggered him. He
had still his qualms, and evidently doubted whether he should not
raise his price a third time. I saw no safety but in pertinacity and

firmness, and had the good fortune ultimately to check his doubtful,
half-formed experiments.
I was led by the accidents which have just been related, into
further and deeper reflections on the power of money, as well as on
the nature of the situation in which I found myself placed by the
legacy of the stranger. My present experiment had been made upon
a subject apparently the most favourable that could have been
devised, upon a man whose breast the love of gold occupied without
a rival: yet with this man I very hardly succeeded. I was not indeed
so blinded by the present dejection of my spirit and sickness of my
heart, as to imagine that I had not a secure game with this base-
minded wretch, if I consented to play it. I had only to enlarge my
bribe, to change it from the limited sum of two thousand pounds to
the more brilliant offer of two thousand per annum, and no doubt I
might have led him with me to the extremity of the globe. However
he might have demurred, however he might have doubted, however
curiosity, whetted even to agony by the goadings of avarice, might
have prompted him to an incessant enquiry within himself as to the
solution of my character and my powers, his grasping spirit would
infallibly have chained his tongue, and been surety for his fidelity.
But I could not yet prevail upon myself to endow such groveling and
noxious propensities with so rich a reward. I considered, in the
language of the stranger, that the talent I possessed was of the
most momentous nature, and bestowed by the governor of the
universe for the highest purposes; and I should have held myself
unjustifiable in enriching by its means, however urgent the necessity
might appear, the most worthless of mankind.
The sentiments of my tyrant varied every hour; he was fickle,
anxious, and undetermined; harassed with the double fear of losing
the sum already obtained, and of not securing the whole of what
was capable of being acquired. He parted with me at last with all the
pangs of a lover, who witnesses the ceremony of his mistress’s
taking the monastic veil, and being sundered from him for ever. I
was his Fortunatus’s purse, and this was the last day he was to
enjoy the use of it; I was to him as the buried treasure of some

long-forgotten hoarder, and he feared he should quit his digging
before he had carried off every thing that the field concealed. At
length however he began to apprehend that he had urged the
refinement of an unprincipled avarice as far as it would go; and
therefore in a few days, the negro being already discharged from his
penance, he suffered us to escape together.

CHAPTER XXIII.
Having rejoined the remainder of my family, we set out together
for the plains of Italy. My first interview with Marguerite after my
return from Dresden had been melancholy. But our situation was
now such as to give additional anguish to her serious thoughts. She
had then regarded me as ambiguous, mysterious, and impenetrable,
qualities from which the frankness of her nature spontaneously
revolted; she saw in me the destroyer of her son, the idol of her
heart; she believed me an alchymist, a character which she viewed
as base, degrading, and insensible; she had heard that rumour had
been busy with my fame. But now she saw in me a man of blasted
reputation, arraigned and imprisoned for robbery and murder. She
did not credit these imputations. But did the ingenuous and noble-
minded Marguerite de Damville ever think to find herself allied to a
being thus loaded with the world’s abhorrence; that she should be
compelled to honour with the sacred name of husband a fugitive, a
prison-breaker, and an outlaw? If I had suffered these things in the
defence of my children, my religion, or my country, the case would
have been widely different. If, while encountering the contempt of
men, I had carried within me the glorious feeling, that what they
regarded as my disgrace was indeed my immortal honour,
Marguerite de Damville, beyond all women, was prepared to despise
their senseless blame, and proudly to demand her share in such a
dishonour.
I know there are men who will listen with fretful impatience to a
detail of such sorrows as hers, and who will cry out, “If we must be
distressed, give us more substantial and genuine sources of
distress!” They will regard the dejection of Marguerite as an idle
wilfulness of grief, better entitled to aversion than to sympathy; and
will tell me that nothing but the most deplorable blindness could
have prevented her from discerning the happiness of her condition;

that she had the world before her, a rich, a brave, and an
enterprising husband, with a lovely family of children; that they
could move from country to country, and from climate to climate,
carrying with them the means of luxury, indulgence, homage, and
usefulness. To such moralisers I write not. For those who are
incapable of sympathising with the delicate sensations of Marguerite,
I am as little qualified to enter into their feelings as they into mine.
In the sequel of the story however it is not impossible they may
meet with their gratification. I am hastening to events corporeal and
palpable. I and my family did wander from country to country, and
from climate to climate. With what resulting success will speedily be
seen.
Our destination at the present moment led us through the
territory of the Grisons, and over a limb of the Rhetian Alps, to
Como, Milan, Piacenza, Parma, and Pisa, in the neighbourhood of
which latter city we resolved to take up our immediate residence. In
this passage we met with few adventures that merit to be recorded
in my history. One however seems entitled to a place, both as it
tends to display the singular worth of a dumb and unpretending
brute, and as it is in some sort connected with the fortunes I
encountered in the Pisan territory. It occurred in our journey over
the Alps.
One evening, in the wildest and most desolate part of the
mountain, after having lodged my family in an inn, I wandered forth
to take a survey of the neighbouring scenery. It was moonlight; our
travel of the day had been short, and had left on me no impression
of fatigue; while the romantic appearance of every thing around,
tempted me to extend my excursion further than I had originally
purposed. Stories of robberies and murders in the vicinity had been
repeated to us, and Marguerite had employed the precaution of
desiring Hector, such was the name which the caprice of his former
masters had bestowed on my faithful negro, to follow my steps and
hold me in sight. No anticipations of danger however disturbed my
contemplations. I resigned myself, as all my life I had been
accustomed to do, to the impressions of the moment, and sought to

shut out memory and the world from all my thoughts. The scene
was inexpressibly beautiful; the silence was uninterrupted and awful.
The splendour of the moon gave a sober and silvery tint to every
thing by which its light was caught; soft white clouds were scattered
in the deep azure of the sky; the shades were of a blackness and
profundity that could not be surpassed. Every thing was calculated
to soothe and subdue the mind, to inspire a grand and expansive
tranquillity. The enthusiasm it spoke occupied every channel of my
heart. I stood still. It seemed as if motion would have jarred and
broken the spell that seized me; I yielded with eager transport to the
sentiment that shrowded and enveloped me in its ample embrace.
I had remained motionless for above half an hour, when a sudden
and eager sound burst upon my ear. It seemed to be the shriek of
some human creature in distress. It was repeated several times. My
first impulse was to fly to the spot from which the sound appeared
to proceed. Meanwhile Hector came up to me, and endeavoured to
detain me by violence. His first principle was obedience to every just
and lawful command; and the errand upon which he was
commissioned, was to preserve me from the approach of danger. He
represented to me the stories of banditti we had recently heard. He
told me that we should too probably fall in with a numerous party of
these desperadoes, against whom all our efforts, either for ourselves
or for those I was desirous to succour, would be nugatory. What
would become of my children? what would become of his mistress, if
my rashness were succeeded by a fatal event? While he was thus
speaking, and exerting himself to detain me, the cries ceased. I
believed they were those of a person assassinated. I conceived that
I should be the vilest of poltroons if I suffered any consideration to
prevent me from endeavouring to afford to this unfortunate the
relief in my power.
I had not advanced far, before I perceived coming towards us, in
the same direction from which the sound had reached my ear, a dog,
entirely black, and of uncommon stature and strength. He was
alone. Having caught sight of us, he increased his pace, and had no
sooner reached the spot on which we stood, than he seized the flap

of my coat, and pulled it with considerable violence. I was somewhat
alarmed at his size and action, the latter of which I apprehended to
have a hostile design; and, having shaken him off, I put myself in a
posture of defence with a cane that I carried in my hand.
Undeterred however by my gesture, he returned to the attack, only
pulling with something less exertion of strength than he had done
before. More accurate attention convinced me that he had no
intention to injure me, and I withheld the action of Hector, who had
raised his hand to strike in defence of his master. I suffered him to
guide me; and, after a considerable circuit which the nature of the
road obliged us to take, he led me to a spot where I found a man
lying on the ground, and weltering in his blood, but with no person
near, to whom to impute the violence he had sustained.
His blood flowed copiously from two or three different wounds,
one of them in particular near his left breast; and my first care was
to stop the effusion. For this purpose we stripped him of his clothes,
and tore his linen into bandages. When we found him, he was
insensible; but the anguish of binding his wounds revived him a
little, though only enough to extort from him sighs and groans. This
accomplished, I dismissed Hector to the inn to procure something in
the nature of a litter, by which he might more easily be conveyed
within reach of effectual assistance.
I was now left for six hours with no other companions than the
wounded gentleman and his dog, upon the very spot upon which he
had just before sustained so ferocious a treatment, probably from
the hands of banditti. They might every moment be expected to
return. This was no agreeable notion to a person circumstanced as I
was. I was compelled to feel that a man possessed of boundless and
illimitable wealth, and of the power of repelling old age and disease,
did not in these advantages possess every thing. Notwithstanding
the disappointments and mortifications I had sustained, I was yet
attached to life: and though the bequests of the stranger had
hitherto produced to me nothing but evil, I still looked, with almost
puerile eagerness and beating of heart, for the time when I might
spread out the whole extent of my treasures without parsimony or

the dread of reverse. During the interval which I employed in these
reflections, the wounded man was for the most part in a state of
insensibility, and constantly speechless. I expected his death every
moment, and I perceived, as I thought with certainty, that there was
no hope of his recovery. While we had dressed his wounds, the dog
had watched our motions with the most restless attention, and, now
that it was over, he came and licked my hands, and laid himself
down at my feet. The least motion however, so much as a rustling
among the leaves, startled him: he rose, looked round, and seemed
to enquire into the cause of the disturbance; but he abstained from
barking and every kind of noise; whether it were that he was
conscious of the advantage of quiet to a person in his master’s
condition, or that he had the sense to know, in the situation in which
we were placed, that whatever produced alarm, might eventually
expose us to undiscovered danger.
It was broad daylight before Hector re-appeared, and several
other persons in his company. Hector was not of a temper to have
receded from any thing he undertook, and the authority of
Marguerite had in this instance seconded his remonstrances with the
surly and inactive peasants of the place. I had at this time only one
other male servant; but, when Hector returned, he brought with him
a crazy kind of litter, and a recruit of four mountaineers. The
wounded man still lived, and was conveyed alive to the place at
which I had taken up my lodging. He survived three days; and,
during the whole of that period, the dog could neither be moved by
force, nor prevailed on by entreaties, to quit the apartment of his
master. Before his death my unfortunate guest recovered the power
of speech. He told me that his name was Andrea Filosanto, and,
which struck me as somewhat extraordinary, that he was of Pisa, the
very place at which I purposed to take up my abode. He had a
brother resident in that city, and had himself been about to marry a
very beautiful and accomplished young lady, an heiress, of the house
of Carracciuoli in Pisa. Previously to his marriage, he resolved to
make a visit to his mother, who had espoused to her second
husband a French nobleman of Languedoc. He had travelled

accompanied only by one servant, contrary to the persuasions both
of his brother and the family of his intended bride; but that servant,
though he had been a very short time in his employment, was
active, ingenious, and obliging, and had established himself strongly
in the favour of his master. Signor Filosanto had taken with him a
sum of money, the produce of one year’s income of the dower of his
mother; and it was but too probable that the richness of the charge
he bore, had been fatal to the life of the bearer. His servant had
disappeared from his side not a quarter of an hour before his being
attacked by the banditti; and various concurring circumstances
seemed to fix on this servant the accusation of being an accomplice
with the murderers. Having heard from the unfortunate sufferer the
tale of treachery of his human attendant, I related to him the
extraordinary example of fidelity and attachment shown by his dog.
The master was struck with the story I told, and called the dog to
him upon his bed. The poor animal first leaped up upon the foot of
the bed, and then warily and with great caution crawled to his
master’s face. Filosanto embraced the dog, who by his manner
showed himself fully sensible of the purport of the action. That very
evening, having requested me to convey his remains to the tomb of
his ancestors at Pisa, the master expired. The dog in dumb and
constant grief watched by the corpse, and followed the vehicle in
which it was conveyed to Pisa. After the funeral, he made the
choice, from which he could not be diverted, of living with me, and
not with the brother and relations of his master, to whom he was
almost wholly a stranger, but who would gladly have received him.
One of the advantages I derived from this adventure, was the
friendship and protection of the Filosanti and Carracciuoli, two of the
most powerful families in Pisa.
I have not yet finished the history of my dog. A few months after
our establishment in the Pisan territory, the valet of the deceased
had the audacity to appear in that city. He believed himself to be
entirely unknown there, his master having taken him into his service
during his residence as a student in the university of Bologna; and
having ordered him, previously to his projected tour into France, to

stay behind and settle his debts and other affairs at that place. He
found however an adversary in Pisa that in all his anticipations had
never occurred to his thoughts. The dog saw him at a distance in the
street, ran towards him with incredible swiftness, and fell upon him
with savage violence and ferocity. The man was not extricated from
his grip, till he had been severely and dangerously wounded. Thus
assailed, all the terrors of superstition and an accusing conscience
seized on this devoted villain; he owned who he was, and confessed
that he had made one among the assassins and plunderers of his
master, visible probably to the dog, though unseen by the
unfortunate Filosanto. He declared, that he knew not what motive
had brought him to Pisa, that he seemed to himself under the
guidance of an impulse which he had not power to resist, and that
he rejoiced that Providence had thus conducted him to the expiation
of his guilt. He was brought to his trial, and suffered death for his
crime.
Charon, such was the name by which my dog was distinguished,
showed himself in all his actions worthy of the character for
attachment and sagacity which he had in these instances acquired.
He was therefore the favourite of my whole family, and particularly
of Hector. But his own partiality was with the nicest discrimination
reserved for me. The ruling passion of his preceding master had
been the sports of the field, and his leading singularity an
uncommon familiarity and friendship towards his brute attendants.
By this conduct he had won the affections, and perhaps awakened
the understanding and virtues, of the faithful Charon. I own my
weakness. I could not resist the assiduities and regard of this
generous brute; and, though I had never before conceived any
extraordinary partiality for creatures of his species, his sagacity and
nobleness of nature took a strong hold of my affection. I admired his
form and agility as he bounded and gamboled before me upon the
plain. In the midst of his gayest frolics he was all attention, and the
least sign I made him would instantly divert his exertions to a
different pursuit. He was accustomed to salute me with honest,
undesigning homage every morning as I came from my chamber,

and I should have missed his presence with heaviness of heart upon
this plain and homely occasion. He was the associate of my solitary
walks, and my companion when pensive meditations induced me to
withdraw from all human society. I became accustomed at such
periods to observe him by my side, and should have felt that all was
not right if he were not there. I was interested in his health, his well-
being and his enjoyments; and, if any calamity befell him, was
prepared to feel it more severely than a wise man is sometimes
willing to confess.—It would scarcely be necessary to add to this
simple history of my faithful Charon, the circumstance of his having
saved the life of a beautiful little boy of ten years old, who had
unluckily slipped into the Arno, and whom he seized by his garments
and drew to the shore, had it not some connection with what I shall
speedily have occasion to relate.

CHAPTER XXIV.
To return to the thread of my narrative, which in stating these
particulars I have in some points anticipated.—I sat down, as I have
already said, in the environs of the city of Pisa. Marguerite, as well
as myself, had a powerful attachment to the retirement of rural life,
and I judged it equally eligible for the health and intellectual
improvement of my daughters. I accordingly purchased a small
domain, delightfully situated, but of simple appearance, on the
banks of the Arno. Here I proposed to remain during the
indisposition of my wife, which I flattered myself retirement,
tranquillity, attention and kindness, would in no long time be able to
cure. To this object I resolved to devote my exertions. Well did she
merit this return from me, who had restored me in the guilty ruin of
my fortunes, and raised me from the abyss of insanity. Odious and
detestable in the utmost degree should I have appeared in my own
eyes, if I could have neglected any means I was able to devise, to
heal a mischief of which my own precipitation, selfishness, and folly
were the only causes. Every little, continual, nameless care I
exerted, was as a drop of healing balm to the burning fever and
remorse of my conscience. Nothing indeed could eradicate my
distemper; I felt the ever-living worm of perpetrated guilt gnawing
at my heart. But my solicitudes for Marguerite, at least during the
moments they were in action, mitigated my anguish; and this
transitory relief, however insignificant it may appear in the eyes of
others, I cherished beyond the wealth of kingdoms.
Marguerite and myself appeared at this time to have changed
characters. She was languid, indisposed in body and mind, her
thoughts gloomy, her hopes blasted, her wishes bankrupt. Still
however she maintained her superiority to what I had been in a
similar condition. She endeavoured to make the best of what yet
remained to her, though she declined the vain attempt of forgetting

what she had lost. She hung over her daughters with inexpressible
endearment. She consoled them; she reasoned with them; she
endeavoured to steel their minds for whatever ill might be yet in
store. She cultivated their understandings; she breathed into them
mingled sentiments of resignation and energy. There was in her
conversation with them a striking tone of celestial and divine. Her
eloquence was copious; her manner rich, unaffected, and flowing;
her speech simple, free from exaggeration and turbulence, but mild,
affectionate, and winning. It sank deep into the hearts of her
hearers, and seemed to give a new turn to their tempers and
disposition. It rendered the character of Julia at once more
distinctive, and yet more chastised; it inspired an unwonted mildness
and sensibility to that of Louisa; and rendered the cadette of the
family unusually grave, thoughtful, and sedate.
But upon me were devolved the more active occupations of our
establishment. Marguerite had formerly been, I was now, the
steward. Every kind of superintendence, from which the distinction
of sex did not unavoidably exclude me, was resigned to me by the
lovely victim of my indiscretions. Marguerite had been my nurse, I
was now ambitious to be hers. I made myself the schoolmaster of
my children; Marguerite confined her communications to general
topics and the culture of the heart. I initiated them in music,
drawing, geography, several different languages of Europe, and in
every accomplishment that I believed would be really ornamental or
improving to them. I might, it is true, have hired different masters to
instruct them in each of these branches, and it is not impossible that
they might then have been better taught, though I was myself no
incompetent preceptor. But I had an honest artifice for my guide in
the plan I adopted: I was desirous of removing out of the sight of
my wife every thing that might remind her of the fatal legacy, the
effects of which she was induced so bitterly to deplore. In some
particulars I may affirm of myself that I was now a better and a
kinder husband, than I had been in the days of our gayest
prosperity, or the scene of our infant loves. I studied with assiduity
the temper of Marguerite; I watched her looks; I endeavoured to

anticipate her every wish. I meditated with care the plan of life,
which her simple and feeling heart, if solely consulted, would have
led her originally to have chosen; and I copied out in the whole
arrangement of our household the idea painted in my mind. Far from
us were now the ostentation and pomp of the family-château on the
banks of the Garonne. We lived now, not to awaken admiration and
envy in the bosom of guests and spectators: we lived for ourselves.
Every thing was elegant; every thing was tasteful; but not an article
found its place in our residence, that did not rest its claim to be
there upon a plea of usefulness. Though, by the nature of my
situation, I was superior to all restraint from a consideration of
expense, yet our competent board and orderly habitation
approached nearer in their appearance to the honest plainness of a
rustic, than to the sumptuousness of hereditary nobility. A table set
out with striking propriety and neatness was preferred to the
richness of plate and the splendour of porcelain and lustres. I was
anxious that Marguerite should forget the change of our situation
and the extent of my resources. The objects of my present pursuit
were obscurity and content. That Marguerite might forget my
acquisition, I was studious to appear to have forgotten it myself. If a
stranger had entered our habitation, and surveyed our economy, he
would have judged that our revenues amounted to a decent
competence, and that we disbursed them with a judicious discretion.
Nothing was to be seen that would have betrayed the possessor of
the powder of projection.
We had no guests. We cultivated no acquaintance. We were
formed to suffice to each other within our little circle; and, but for
the importunate recurrence of disquieting reflections, we should
have done so. To look at the exterior of our household, it might have
been thought that we had arrived at that sweet forgetfulness of
anxious care, that delicious leisure and unbroken retreat, which have
in all ages been the theme of panegyric to poets and philosophers.
But it was not so. Our reciprocal relations were changed; and the
hope of the house of St. Leon was no longer in the midst of us, to
cheer, to enlighten, and to warm our bosoms.

A life of leisure is often an active and a busy life. The grand, I
might almost say the single, object of present attention to me, was
the restoration of the health and tranquillity of Marguerite. For that I
watched with unwearied assiduity. Subordinate to this occupation
were the different arts and accomplishments in which I instructed
my daughters. Yet neither the former nor the latter of these
engagements filled up all the time of a mind so restless and rapid as
mine was. Intervals occurred, in which my attentions to Marguerite
would have been, not soothing, but troublesome, and in which I
could no longer impart a lesson to my daughters, without relaxing
and weakening the spring of progression in their minds. These
intervals I sometimes dedicated to chemistry and the operations of
natural magic. The more effectually to hide these pursuits from the
eye of Marguerite, I occupied, unknown to her, a sort of grotto,
buried almost from human observation in a hollow on the banks of
the river, and which was connected, by a winding path and a
concealed subterranean passage, with the garden of my own
habitation. The secrets of the stranger had given me a particular
relish for this kind of pursuit. There are habits of the mind and
modes of occupying the attention, in which, when once we have
engaged, there seems a sort of physical impossibility of ever
withdrawing ourselves. This was my case in the present instance. My
habit was of no long standing. But no reading of my story, no mere
power of language and words, can enable a bystander to imagine
how deep it was sunk into my heart, how inextricably it was twisted
with all the fibres of my bosom. That he may in some degree enter
into my situation, I entreat the reader to consider what are the most
imperious passions of the human mind. They have rudely been
described to be wealth, power, and pleasurable sensation. How
alluring to every one of us are the visionary conceptions of the mind
respecting these most potent excitements! But mine were no visions.
I had grasped them in my hand, and known their reality. I had felt
that the wealth of the whole world was at my disposal, and that I
held my life by a tenure independent and imperial. These are not of
the class of conceptions that fade and perish from the mind. We
cannot wake from them as from a dream, and forget that ever such

things were. They had changed the whole constitution of my nature.
It would have required a miracle, greater than all the consecrated
legends of our church record, to have restored me to what I
formerly was. If then I could have resolved never henceforth to use
the gifts I had received, I yet firmly believe that I never could have
refrained from the composition and decomposition of simples, and
from experiments on the nature of substances, chemical and
metallic. I was however far from having formed any such resolution
as that I have named. My present forbearance to bring forth the
secret treasure of my powers was purely an accommodation to the
unhappy condition of my wife; and I felt it as a meritorious exertion
thus to postpone the use of the faculties I possessed. In the mean
time the amusement I sought, that I regarded as properly and
entirely my own, consisted in these experiments. While I was busied
with my crucible, I was able more vividly to present to myself my
seeming superiority to the rest of my species. I used the
employments of my grotto, as a sort of starting-post from which to
set forth in a series of intoxicating reveries; not to mention that to
improve in the facility of my secret operations might become a
valuable subsidiary to the pursuits of my future life.
I took occasionally as my companion at these periods the negro of
the prison of Constance. I found him sufficiently adapted for my
purpose; his innocence and implicit obedience to whomever he
served, rendering me secure that he would anticipate nothing, that
he would conjecture nothing, that he would rest in what he saw,
that I might almost exhibit my whole process under his eye, without
once awakening the busy fiend of curiosity in a mind to which
science had never unveiled her charms. He was formed to be a pure,
passive machine in the hands of his employer, only with this singular
difference from the lifeless machine of the engineer or mechanical
inventor, that he was susceptible of attachment and affection, as
well as of a certain species of contentment and a certain species of
goodness and virtue.
A feature of my individual character which has already frequently
presented itself to the attention of the reader is the love of

admiration and spontaneous deference. I am at this moment
ashamed of my vices and my follies; but it must be recollected, in
the first place, that they are human, and in the second that I am
writing, not their vindication, but their history. In the midst of my
experiments and chemical lucubrations, I could not help sometimes
ostentatiously exhibiting to Hector the wonders of my art, and those
extraordinary effects which have in all ages drawn upon the more
eminent operators of natural magic the reproach of being
necromancers and conjurers. This I did, partly perhaps that my
attendant might learn to look up to me with a kind of nameless
respect and awe, but partly also that I might divert myself with the
simplicity of his nature, and the gaping and motionless astonishment
with which he viewed my performances. If I had not done this, or
digressed into idle and ostentatious experiments, he would
otherwise have seen enough, in the operations in which his
assistance, if not absolutely necessary, was extremely convenient, to
have induced a person, so void of the meanest European
information, to regard me as assisted by and in league with invisible
powers.
The prejudice against me, with which this poor fellow had been
impressed at the commencement of our intercourse did not long
hold out, in his ingenuous mind, against the more favourable
sentiments which my present situation and mode of living were
calculated to inspire. The specimens he had hitherto seen of
European society were of the most unfavourable kind. His first
master was a wretch of brutal disposition, ferocious and insolent;
disdaining to reason himself, and impatient of remonstrance in
others. This man had exercised the temper of his humble and honest
attendant with every variety of savage caprice; and, having tired the
restlessness of his own gloomy tyranny, without being able to
exhaust the modest and unexampled patience of his servant, had
finished by throwing him into gaol, upon a wanton and groundless
charge of dishonesty. This, which was intended as a further exercise
of tyranny, deserved to be hailed by the poor sufferer as a period of
jubilee and deliverance. His innocence, as I have already related,

was speedily recognised by his new task-master, who accordingly
exerted himself to obtain justice for the friendless victim; and from a
reputed thief proposed to elevate him to the rank of a turnkey.
Hector had neither kindred nor patron to assist him; the outcast of a
gaol, he must again have entered the world with a blasted character.
Thus circumstanced, and influenced beside by gratitude to the
unlooked-for liberality of his deliverer, he willingly accepted the
situation proposed to him. With his new master, who, not less
unprincipled, was less tyrannical than his predecessor, the
humbleness of his hopes taught him to be contented. Yet in the
bosom of the gaoler all his fidelity and regard could not enable him
to detect one positive virtue; and, within the walls of the prison,
there had existed nothing that could by any possibility cherish and
refresh the human heart.
The scene presented to Hector’s observation in our little retreat,
on the banks of the Arno, was of a very different nature. To his frank
and affectionate spirit, it appeared a perfect paradise. He had yet
scarcely been acquainted with any but the refuse of mankind, from
the infection of whose vices his unapprehensive and invincible
simplicity had been his only safeguard; and he was now suddenly
introduced to the presence and intercourse of the most perfect of
her sex. He loved her as a benefactor, and he worshipped her as a
god. There is no receipt for begetting affection in others, so infallible
as a warm and susceptible heart. Hector accordingly soon became in
a remarkable degree the favourite of my daughters. His temper was
naturally cheerful and gay; and, warmed by their encouragement, it
became a thousand times more so. When he had completed the
occupations of the day, the lightness of his spirit would prompt him
to sing and dance for ever. He exhibited the whole circle of his
sportive games for their amusement. The infantine innocence of his
understanding remarkably adapted him to be the butt of their little
waggeries and mischiefs. Whatever tricks were played upon him,
were however tempered by the forbearance and regard his worth
demanded; while the obstreperous cheerfulness with which he
would second their mirth, when most ignorant of its occasion, gave

uncommon zest to the amusement, and furnished eternal
provocation to the prolonging and varying its features.
Let not the fastidious reader complain of the inconsistency of this
part of my picture, or censure the levity of my daughters. I am not
writing a tragedy, but a history. Sad grief and melancholy cannot,
and ought not, for ever to reign in the human face or the human
heart. No daughters ever loved a mother more entirely, more
fervently, than Marguerite was loved by her children. They were
unwearied in their attention to her: often was their pillow watered
with tears, occasioned by the sad presentiment of the loss they were
destined to sustain. But the human mind, particularly in the season
of youth, has an unconquerable principle of elasticity in its frame.
The bow cannot be kept for ever on the stretch; and, when the
whole soul appears to be bent down by calamity to the grave, it will
often surprisingly recover its vigour and renew its strength. The
ingenuous nature of these poor girls led them indeed occasionally to
reproach themselves with these moments of cheerfulness as with a
crime. But it was no crime. None but the uncharitably rigorous and
morose will charge it upon them as a crime. It interfered with no
duty; it diminished no affection; it had no tendency to harden their
hearts. It was a tax they paid to the imperfectness of our nature; it
was a tribute of gratitude to that God who, while he deals out to us
the most terrible calamities, fails not to mix with the copious draught
some solitary drops of beneficence. Julia alone, whose temper was
constitutionally serious and soft, entered little into these sports, of
which her youngest sister was the eternal leader and untired
partaker. Yet even upon the grave countenance of Julia they would
sometimes provoke an unwilling smile, which upon her countenance
sat with uncommon lustre.
The hilarity and loveliness which Hector found in the midst of my
family instigated and increased the attachment he began to feel for
myself. He could not believe that the father of such daughters, and
the chosen husband of such a consort, could be destitute of a title to
be loved. He reasoned in his own way upon the attempt I had made
to corrupt his fidelity, an attack which he never thoroughly digested.

I have reason to believe that his attendance upon my chemical
processes, and the wonders I occasionally showed to excite his
astonishment, did not tend to elevate me in his good opinion. But he
could not avoid witnessing in me many of the virtues of a good
husband and a good father, and these, so new to his observation,
strongly impressed him in my favour. The regularity of my habits and
the mildness of my carriage were also calculated to win his affection
and esteem. Never had the poor fellow’s affections been so forcibly
called out as they were in his new situation; and he would cheerfully
have stretched out his neck to the assassin’s knife, to have warded
off impending evil from the meanest of us.
Prosperity and ease have often been found the parents of wishes
and inclinations unfelt before. Adversity is the season of sober
thought, calls home the erratic mind, and teaches us to be cheaply
satisfied. But the man who has many gratifications is apt to wander
in imagination from daily and familiar joys, and confidently to reach
after things yet untried. Such was the situation of Hector: Hector
was in love. Our sweet and simple mansion was distant scarcely
more than two hundred yards from a characteristic Italian village.
The maid of a little albergo in this place had caught his
inexperienced heart. He had been invited by some peasants to a
moonlight festivity on the lawn of the albergo; and, though I should
have been better pleased that my servants should decline this sort of
amusement, I could not have the heart to deny him. It was, so far
as I knew, the first and the last time that Hector had ever resorted
to it. But I was deceived. Hector had proved the gayest and most
amusing of the whole circle. His cheerfulness was inexhaustible, and
his mirth in the utmost degree harmless and good humoured. He
had played a thousand antics, and danced with an agility that knew
no end. In a word, the accomplishments of Hector, in spite of the
jetty hue that stained his face, had won the heart, or roused the
coquetry, of the plump and rosy bar-maid. The overtures she made
and the lures she threw out were too glaring to escape the notice
even of the modest Hector. He felt himself flattered, such is human
nature, at suddenly becoming an object of admiration and

preference to a woman, whom his imagination, stimulated by her
visible partiality, attired in a hundred charms. He owned himself
hers, in all fair and honest fealty, to the world’s end.
Love taught Hector a lesson which he had never learned before.
In nature he was frank, and, as far as fidelity to his master
permitted it, wore his heart as naked as his face. Love taught him
dissimulation. A vulgar footman or clown is as forward as the most
empty beau, in boasting of the triumphs he has gained over the
female heart, and in sacrificing the reputation of those who have
loved him at the shrine of his vanity. Not such was Hector. He shut
Up his new sensations and reveries as a sacred deposit in his bosom.
Nature worked within him, and he would have been ashamed to
speak, and distressed to hear, of emotions, now felt, till now never
experienced. His artless and ingenuous temper in this one particular
assumed the guise of cunning. Never did he tell his love in the ear of
any indifferent auditor; assiduously did he avoid pronouncing even
the name of her to whom he was attached. In any other case he
would have announced to me his inclinations, and previously
demanded my leave of absence for his excursions. But love seemed
to him imperiously to command privacy, and he employed every
imaginable precaution to prevent me and all human beings from
knowing whither he went, or that he was absent at all.
In one of his visits to his fair donzella, he happened incautiously to
drop some very remote hint of the scenes in which he had just been
engaged with me in my secret grotto. The curiosity of the girl was
strongly roused; she questioned him further. He started, and was
terrified to recollect what he had said. I had strictly enjoined him
secrecy towards every member of my family: my precaution had
extended no further; for, as I have said, I scarcely knew that he had
the most casual intercourse with any person beyond my own roof.
But Hector naturally dreaded that what I was so earnest to conceal
from every one in my house he would be highly to blame to
communicate to a stranger. He therefore peremptorily refused, and
with many signs of distress, to say another word on the subject.

The donzella, piqued at his resistance, had recourse to female
arts. She was cruel; she uttered words of sharp displeasure and
disdain; she knew that a person who refused her such a trifle could
not have an atom of regard for her; she commanded him never to
see her more. Unsuccessful in these expedients, she had recourse to
expedients of a different sort. She wept; she called him base, false-
hearted and unkind; she saw he was determined to be the death of
her; she was seized with strong fits of sobbing and hysterical
affection. In the midst of all this he was as unmoved as a rock of
marble. He interpreted every thing that passed in its most literal
form; he felt more severely her unkindness, and sympathised more
truly in her distress, than perhaps any human creature would have
done. But no further could she gain upon him. The confidence of his
master was in question, and he would sooner have died upon the
rack, than run the slightest risk of betraying it.
From these arts she descended to arts more congenial to the
habits of her life. She summoned all her skill to perplex him with
cunning and insidious questions. From her questions he ought to
have fled; but of this Hector was incapable. He was distressed by
her severity, he grieved for the unintentional pain he had caused her.
All these circumstances melted his heart; and he could not resolve
upon any thing that was not considerate and respectful towards her.
As the framing of artful questions was the strong-hold of the
donzella, and she might have challenged in this article the most
hoary practitioner of the quibbling bar, so it was exactly the weakest
side upon which poor Hector could be attacked. His simplicity yielded
him up a defenceless prey to the assailant; least of all human
undertakings was he capable of detecting the various faces of a
doubtful question, and of guarding himself against the traps of an
insidious foe. It was not till the fourth interview from Hector’s
original hint, that the donzella had recourse to this species of attack;
and she did not withdraw her forces, till she had extorted from him
all he knew.
When Hector found that all his guards were baffled and put to
flight, he had then recourse to the only expedient that remained,

conjuring her by every thing sacred and every thing tremendous, not
to betray a trust she had so ungenerously obtained from him. She
readily promised every thing he desired. Soothed by her compliance,
he determined not to mention to me the lapse of which he had been
guilty. It would in his opinion have been little less than treason, to
suspect his Dulcinea of indiscretion or frailty. In the breast of this
miracle of nature was not his loyalty as secure as it could be even in
his own? Why then should he betray the secret of his love, which
had never yet been confided even to the senseless air? Why should
he subject himself to the inconceivable anguish and confusion, of
owning, where my interests, or where my wishes were concerned,
that he had been found tripping and imperfect? Why should he inflict
a pain, or cause in me a fear, which he knew, and he only could
know, was groundless? Thus it happened that I had one more
confident of what I purposed should be secret, than I was myself in
the smallest degree advertised of.
The consequences of this indiscretion of my servant were not slow
in rendering themselves visible. The donzella was by no means so
scrupulous or delicate in her sentiments, as my humble, but faithful,
attendant. As she had given her company to Hector, she had had an
opportunity of observing in him such integrity and goodness of
heart, as could not fail to extort the esteem of any human being.
She really honoured him; she was unwilling to give him any cause of
uneasiness. But she had another lover; perhaps she had more. The
laws of chastity she regarded as prejudices, and believed they were
never formed for persons in her situation in society. She was of
opinion that the more lovers she had, provided she satisfied them
all, the more completely did she improve the talents with which
Heaven had endowed her. Few women have any secrets for the man
they admit to their embraces. In an hour of amorous dalliance she
communicated to Agostino, the ostler, all that she knew of the
conjurations and spells of Monsieur Boismorand, such was the name
I had assumed upon my entrance into Italy. Her communication was
probably attended with cautions, imitated from those with which
Hector had so industriously loaded the donzella in the preceding

example. Perhaps the illustrissimo Agostino had another mistress,
with whom he thought it would be unjust to practise greater
reserves than the donzella had done with him. Be that as it will, the
rumours which were whispered to my prejudice speedily got air;
and, it may be, were repeated with the greater avidity, on account of
the mystery that attended them, and the injunctions of secrecy with
which they were accompanied.

CHAPTER XXV.
Italy may be considered as the very focus and parent of
superstitious credulity. The materials which Hector had furnished,
after all the interrogations of the donzella, were slight compared
with the superstructure which was presently erected on them. My
grotto was said to be the appropriated haunt where a thousand
devils held their infernal sabbath. The terrified imagination of the
rustics, listening with a temper horribly distracted between curiosity
and alarm, created to itself fictitious howlings and shrieks, and saw
pale and sulphureous flames dancing upon the surface of the
stream. Poor Hector was early the victim of their cruel and untamed
ignorance; they believed that the peculiarity of his complexion
rendered him a singularly agreeable intercessor between me and my
infernal familiars. The colour of Charon was similar to that of my
confidential attendant; and he, like Hector, fell under the calumnious
misconstructions of the affrighted villagers. Conspicuously noble,
affectionate and useful as he was, the jaundiced eye of superstition
metamorphosed him into a devil. The storms of thunder and
lightning to which the climate in which I resided is particularly
subject acquired new terror from the ill fame which now pursued the
name of Monsieur Boismorand. At those times the shapeless form of
monsters vomiting smoke and flames were visible to the
neighbourhood, sometimes scudding along the blue tops of the
distant hills, and at others, with audaciousness incredible, brushing
even at the elbow of the almost lifeless clowns and dairy-maids, and
then suddenly dissolving into air, their place no longer marked but by
the noisome and deadly stench they left behind. All the misfortunes
of the district were imputed to me, the mortality of cattle, the
convulsions and death of children, and the pale and lingering decay
of persons recently advanced to an age of puberty. Innocent and
blameless was my conduct to all around us; often was I forward and

eager for the relief of the poor and afflicted; never was I the author
of the slightest inconvenience or prejudice to any. Yet nothing
merely human could be hated in the degree in which I was hated;
few were daring and intrepid enough to repeat the very name I
bore; and, when it was inadvertently pronounced, it produced
through the whole extent of the astonished circle an involuntary and
supernatural shudder.
Agostino, the first lover who had made an impression on the heart
of Hector’s donzella, was, as I afterwards found, a fellow of a
gloomy and ferocious disposition, a true Italian spadaccino,
determined that none should perpetrate an affront against him with
impunity, but should expiate, in some refined and cruel vengeance,
the levity by which they had been so unfortunate as to give birth to
his hatred. He by no means relished or approved the liberal and
good-humoured sentiments of the donzella; often had they inflicted
on him the darkest torments of jealousy; nor had he failed, at least
in one preceding instance, to make his rival the victim of his
resentment. The donzella however went on in her career; she was
light of heart, gay in temper, and careless of consequences. She had
always hitherto succeeded, by playful blandishments, or more
serious demonstrations of contrition, in mollifying the temper of her
brute; and every pardon she received operated with her as a new
permission to offend. She did not sufficiently consider that she was
thus continually raising to a higher pitch the frenzy of his malice.
Hector in the mean time was utterly unconscious and ignorant of the
perilous situation in which he stood; while, to the apprehension of
Agostino, the giving him a negro for a rival, whom his pride regarded
as belonging to an inferior species of beings, and his devout
ignorance likened to the leader of the infernal squadrons, was the
last and most intolerable insult.
His malice was ingenious and subtle. He disdained the vulgar
revenge of stabbing his antagonist in the dark, and supposing that
his enmity could be gorged by a blow. When the venom of his
nature was thoroughly put in motion, nothing could restore it to
quietness and tranquillity but some mighty stroke, to excite the

wonder of every bystander, and that should leave behind it a track of
desolation, never to be filled up again and erased. He heard
therefore with unsated appetite and eager joy the tale of
necromancy and infernal machination repeated to him from Hector
by the donzella. The impression which the narrative produced upon
him was a mixed sentiment of transport at the apprehension of such
an instrument of vengeance and of palpitating hatred; superstition
teaching him to believe and to view with abhorrence that which he
desired to render tenfold more an object of faith and aversion to his
neighbours. He struck an auspicious and august alliance between his
revenge and his religion; his religion exciting him to exterminate
that, the destruction of which would produce inexpressible
gratification to his revenge. The darkness of his spirit led him to
proceed with double caution and vigilance in his correspondence
with the donzella. He discovered nothing to her of the dark project
which was engendering in his mind; and only betrayed so much of
his superstitious feelings and fears as, by giving new emotion, might
stimulate her to gratify his curiosity and her own by a detection of
further particulars. He was assiduous in the underhand and sinister
propagation of the tale, to which he did not fail to give his own
colouring and affix his own feelings. He was desirous that the train
should be laid in silence, and that the explosion he designed should
be free from all pre-signification of the event. Thus an individual, of
whose animosity I had no apprehension, and the meanness of
whose appearance would probably have made me neglect all
precaution against him, gave method and direction to an evil, of
which however, upon a review, I am not inclined to doubt I should
have been the victim, if the enmity and industry of this individual
had been wholly withdrawn.
The mischief was long in preparation, before I received in any way
the slightest intimation of the predicament in which I stood. The first
circumstance at all calculated to excite alarm in my mind, was the
singular manner in which I found myself regarded, if I entered any
of the neighbouring villages, or met the rustics and their dames, as I
strayed along the roads or the fields. They fled my approach,

deserted the streets, and carefully shut themselves up in their
houses, till I had passed. Where it was impossible to avoid me, they
bowed themselves to the earth in the most submissive guise before
me, while the most lively terror was painted in their countenances,
dreading lest they should excite the resentment of a tremendous
and inexorable foe. These tokens however were far from inspiring
me with a conception of the truth. They perplexed, they astonished,
they distressed me. Sore as I was with my recent afflictions, my
mind was but too fully prepared for anticipations of evil. I had
suffered from suspicions, I had suffered from calumnious
imputations, I had suffered from the malignant effects of popular
rumour. Had I yielded my confidence to any person but such a one
as Hector, it is probable my suspicions would have turned on that
side. But my reliance on him was not less than that which Alexander
the Great yielded to Philip the physician: I knew his rectitude, his
simplicity, his fidelity, and the singleness of his heart; and I could not
harbour the shadow of a doubt respecting him. My reliance was of
that entire and perfect sort, which did not express itself by a
recollection of the physical possibility and an acquittal founded in
deliberation, but by a total vacancy of doubt, or of retrospect that
way directed, just such as the state of my mind would have
appeared, if the thing had been naturally impossible.
I was not however ignorant and raw enough to be deceived by the
exterior of homage I have described; I sufficiently knew that what I
beheld was the offspring of hatred. To feel one’s self hated is in all
instances a painful and humiliating state of the human mind. To me
it was especially so. I was not formed to retaliate this species of
injury; I could not hate in my turn. I was formed to love. I could not
look upon my species with dark and gloomy contemplations; I was
prompt to admire their virtues, and perhaps even too prompt to
extenuate their errors. It may, I believe, be laid down as a rule, that
they who cannot hate can least endure to be made objects of
hatred. Fettered however as I now was, by the tenderest
consideration for the health and tranquillity of Marguerite, I thought
it best to temporise and submit in silence. My principal anxiety was

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