The Evolutionary Ecology of Ant-Plant Mutualisms

193 Pages·1985·4.64 MB·English

by  Andrew James Beattie

The evolutionary ecology of ant-plant mutualisms
CAMBRIDGE STUDIES IN ECOLOGY
EDITORS:
E. Beck Department of Plant Physiology, University of
Bayreuth
H. J. B. Birks Department of Botany, University of
Cambridge
E. F. Connor Department of Environmental Science,
University of Virginia
ALSO IN THE SERIES
Hugh G. Gauch, Jr. Multivariate analysis in
community ecology
Robert Henry Peters The ecological implications of
body size
C. S. Reynolds The ecology of freshwater phytoplankton
K. A. Kershaw Physiological ecology of lichens
Robert P. Mclntosh The background of ecology:
concept and theory
The evolutionary
ecology of
ant-plant mutualisms
ANDREW J. BEATTIE
Northwestern University
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© Cambridge University Press 1985
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no reproduction of any part may take place without
the written permission of Cambridge University Press.
First published 1985
A catalogue record for this publication is available from the British Library
Library of Congress Cataloguing in Publication data
Beattie, Andrew J. (Andrew James), 1943—
The evolutionary ecology of ant—plant mutualisms.
(Cambridge studies in ecology)
Bibliography: p.
Includes index.
1. Ants — Ecology. 2. Ants — Evolution. 3. Insect—plant
relationships. 4. Botany — Ecology. 5. Plants —
Evolution. 6. Insects - Ecology. 7. Insects - Evolution.
I. Title. II. Series.
QL568.F7B36 1985 595.79'6'0452482 84-27411
ISBN-13 978-0-521-25281-2 hardback
ISBN-10 0-521-25281-4 hardback
Transferred to digital printing 2005
To my mother and father,
Christine, and Helena

Contents
Preface page ix
1 Introduction 1
2 Origins and early evolution of ant-plant mutualisms 8
Ants and plants in the Cretaceous 8
The impact of the ant's mode of feeding 11
The impact of social organization 15
Early ant-plant habitats 19
3 Plant protection by direct interaction 21
Ant nests and domatia 27
Food bodies 34
Extrafloral nectaries 37
A closer look at ant guards and extrafloral nectaries 50
4 Plant protection by indirect interaction 54
Homopterans 54
Lepidopterans 61
Summary and conclusions 63
5 Myrmecotrophy 66
6 The dispersal of seeds and fruits by ants 73
The predator-avoidance hypothesis 73
The competition-avoidance hypothesis 75
The fire-avoidance hypothesis 76
The dispersal-for-distance hypothesis 77
The nutrient hypothesis 77
Assessment of the hypotheses 78
The distribution and variability of ant dispersal 87
The ants that disperse seeds 90
vn
viii Contents
7 Ant pollination 96
8 Food rewards for ant mutualists 110
Ant nutrition 110
Elaiosomes 113
Extrafloral nectar 115
Food bodies 118
Rewards offered by homopterans and lycaenid larvae 119
Ant rewards: supply and demand 120
9 Variation and evolution of ant-plant mutualisms 128
Generalist versus specialist 130
Selection and fitness 131
Pathways to mutualistic interaction and coevolution 138
References 146
Index 177
Preface
The natural history of ant-plant mutualisms has fascinated Western sci-
entists for roughly two centuries. During this time it has become clear
that the ways in which plants manipulate ants, and vice versa, can be so
complex and subtle as to severely stretch the credence of the observer.
The early natural historians described ant-plant relationships in superb
detail, but generally inferred that a given relationship was mutualistic
from anatomical, morphological, or behavioral data alone. Experimental
verification was the exception rather than the rule. Although the experi-
mental approach was tried by a few early workers, such as von Wettstein
(1889), its impact was not dramatic until the publication of Janzen's
seminal work on acacia ants about twenty years ago. This pioneering
research has since been followed by many excellent experimental field
studies embracing a variety of ant-plant mutualisms from many kinds of
environments. Our knowledge of the selective pressures that produce the
mutualistic response, the dynamics of the ant-plant interactions, the
benefits to the plants and the ants, and the ways that mutualisms evolve
has been vastly improved. At the same time, ant-plant mutualisms are
extremely numerous and varied, and so far only a very few cases have
been adequately analyzed. As a consequence, generalizations from limited
data often have to be made. Whether or not this is wise will be revealed
as new studies are published.
Ideas and syntheses generally enter the mind as a result of the stimulation
of colleagues. I have been fortunate in having been at the receiving end
of a great deal of stimulation, especially from Bob Abugov, Lin Chao,
David Culver, Fran Hanzawa, Carol Horvitz, Dennis O'Dowd, Doug
Schemske, Bob Taylor, and Christine Turnbull. Carol Horvitz, Doug
Schemske, Dennis O'Dowd, and Herbert and Irene Baker have kindly
allowed me to use some of their unpublished data. Comments and criti-
cisms by Lin Chao, David Culver, Carol Horvitz, and Dennis O'Dowd of
early drafts of various chapters have led to enormous improvements in
the manuscript. I thank them for all the time and effort they put into
IX