Herbivory of Leaf-Cutting Ants: A Case Study on Atta colombica in the Tropical Rainforest of Panama

235 Pages·2003·9.71 MB·English

by  Dr. Rainer Wirth

Ecological Studies, Vol. 164
Analysis and Synthesis
Edited by
I.T. Baldwin, Jena, Germany
M.M. Caldwell, Logan, USA
G. Heldmaier, Marburg, Germany
0.1. Lange, Würzburg, Germany
H.A. Mooney, Stanford, USA
E.-D. Schulze, Jena, Germany
U. Sommer, Kiel, Germany
Ecological Studies
Volumes published since 1997 are listed at the end of this book.
Springer-Verlag Berlin Heidelberg GmbH
R. Wirth H. Herz R.T. Ryel W. Beyschlag B. Hölldobler
Herbivory
of Leaf-Cutting Ants
A (ase Study on Atta colombica
in the Tropical Rainforest of Panama
With 82 Figures, 16 in Color, and 32 Tables
" Springer
Dr. Rainer Wirth
Universität Kaiserslautern, Fachbereich Biologie, Lehrstuhl für Allgemeine Botanik,
Postfach 3049, 67653 Kaiserlautern, Germany
Dr. Hubert Herz
Universität Würzburg, Theodor-Boveri-Institut für Biowissenschaften,
Lehrstuhl für Verhaltensphysiologie und Soziobiologie (Zoologie 11),
Am Hubland, 97074 Würzburg, Germany
Prof. Dr. Ronald J. Ryel, Department of Forest, Range and Wildlife Sciences,
Utah State University, 5230 Old Mai! Hili, Logan, Utah 84322-5230, USA
Prof. Dr. Wolfram Beyschlag
Universität Bielefeld W 4-107, Lehrstuhl für experimentelle Ökologie und Ökosystembiologie,
Universitätsstr. 25, 33615 Bielefeld, Germany
Prof. Dr. Bert Hölldobler
Universität Würzburg, Theodor-Boveri-Institut für Biowissenschaften,
Lehrstuhl für Verhaltensphysiologie und Soziobiologie (Zoologie 11),
Am Hubland, 97074 Würzburg, Germany
Cover illustration: by Dr. Damond Kyllo, University of Missouri, USA. The illustration is a visual
homage to the leaf-cutting ants and their tropical rainforest environment as perceived by both
the artist and authors after many years of living and working on Barro Colorado Island.
ISSN 0070-8356
ISBN 978-3-642-07865-1
Library of Congress Cataloging-in-Publication Data
Herbivory of leaf-cutting ants: a case study on Atta colombica in the tropical rainforest
of Panama 1 R. Wirth ... [et al.l.
p. cm. --(Ecological studies, ; v. 164)
Inc1udes bibliographical references (p. ).
ISBN 978-3-642-07865-1 ISBN 978-3-662-05259-4 (eBook)
DOI 10.1007/978-3-662-05259-4
1. Atta colombica--Ecology--Panama--Barro Colorado Island. 2. Rain forest
ecology--Panama--Barro Colorado Island. 3. Insect-plant relationships--Panama--Barro
Colorado Island. I. Wirth, R. (Rain er), 1964-11. Series
QL568.F7 H47 2003
595.79'6--dc211 2002030473
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Originally published by Springer-Verlag Berlin Heidelberg New Yo rk in 2003
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For Edward O. Wilson,
premier myrmecologist,
naturalist, and ardent advocate
for biodiversity research,
in appreciation for his many pioneering
contributions to our understandig
of leaf-cutting ant societies.
Preface
The idea for this study was born at the University ofWürzburg, Germany, dur
ing the time when two of the authors (W.B. and R.J.R.) were working on the
effects of ne edle loss of dedining red spruce trees on the light microenviron
ment within the forest canopy. In this system it could be shown that the par
tial loss of foliage led to a significant increase in photosynthetically active
radiation within the canopy which then benefited the remaining healthy
foliage, particularly in dense canopies. Since Würzburg is one of the places in
Germany where interdisciplinary biological research has a long tradition,
these results were also discussed with zoologists. One of them (B.H.) became
particularly interested because one of his major research interests was leaf
cutting ants, an organism which creates substantial foliage losses in the
canopies of Neotropical rainforests. Quickly it became obvious that by com
bining the experience ofboth botanists and zoologists it would be possible to
quantitatively assess the impact of these selective herbivores on their natural
ecosystem, an important question which at that time had never been
addressed before, although leaf-cutting ants, because of their importance as
pests, certainly belonged to the most studied insect species of the Neotropics.
As a starting hypothesis, it was formulated that leaf-cutting ants, by continu
ously creating small gaps in arainforest canopy where light is typically a
major limiting resource, would allow light to penetrate deeper into the
canopy, thereby providing opportunities for species of the middle and lower
canopy and, thus, perhaps contribute to the high biodiversity. Very quickly it
became dear that testing this hypothesis was not an easy task to achieve,
because such ant-induced changes in the canopy light dimate could, of
course, not be analyzed without substantial quantitative information on rain
forest canopy structure, distribution and activities of the ants, herbivory
rates, and the response of the affected plants to this herbivory. Furthermore,
after a doser look, it became dearer that leaf-cutting ants do affect much
more than just the light resource, and leaf-cutting ant-induced disturbance
occurs at multiple scales - from the single plant all the way up to the ecosys
tem. Unfortunately, information on the spatiotemporal herbivory patterns of
leaf-cutting ants was scarce and long-term studies on this subject were prac
tically missing. Hence, more and more dimensions and scales had to be
VIII Preface
included into our considerations and finally we ended Up designing a major
integrated and interdisciplinary ecosystem research project. Not surprisingly,
after the fieldwork had started, unexpected results (for instance, the high fre
quency of ant colony movements) added even more aspects, and what was ini
tially planned as a 2-3-year study, became a major enterprise lasting a total of
8 years, including 5 years of fieldwork.
Nevertheless, looking at the results, we can say that working on this project
for such a long time not only answered quite a few of our questions and, thus,
increased our knowledge of the ecological role of leaf-cutting ants, but most
importantly also provided fundamental insights into the functioning of the
rainforest ecosystem for each of uso We hope by writing this volume we were
able to transport not only our scientific results and ideas (many of them orig
inating from the doctoral theses of R.W. and H.H.), but also our excitement
about these fascinating animals and their extraordinary habitat.
This study would not have been possible without the help and the input of
quite a few people and organizations. First, we would like to thank the Smith
sonian Tropical Research Institute for permission to use their research station
on Barro Colorado Island in Panama and we gratefully acknowledge the help
of their administration in Balboa and the staff of the research station. In par
ticular, we would like to thank the station's scientific coordinator Mrs. Oris
Acevedo for her incredible support. We are grateful for all the help and stimu
lation of the STRI staff scientists, particularly Dr. Egbert Leigh and Dr. Klaus
Winter. Further, Mr. Eduardo Sierra t, Mr. Rolando Perez, and their colleagues
contributed their valuable experience in determining plant species (particu
larly from small harvested fragments). The following student workers and
graduate students were involved in the fieldwork and contributed valuable
data material: Jürgen Berger, Eva Cue-Bär, Querube D. Fuenmayor, Ralf
Hömme, Dorkas Kaiser, Boris Leymann, Mir Rodriguez Lombardo, Andreas
Meier, Stefanie Rottenberger, Gerold Schmidt, Antje Siegel, and Alexandra
Weigelt. Many ideas would never have been created without the inspiring dis
cussions and the valuable input of the following scientists: Dr. Elisabeth
Coley, Dr. Cameron Currie, Dr. William Eberhard, Dr. Bettina Engelbrecht, Dr.
Allen Herre, Dr. Jerry Howard, Dr. Tom Kursar, Dr. Egbert Leigh, Dr. Flavio
Roces and Dr. Thomas Seeley (thanks to both for critically reading the natural
history chapter), Dr. Thomas Steinlein, and Dr. Mary Jane West-Eberhard. Dr.
Edward O. Wilson gave us permission to use some of the material from publi
cations of which he was author or coauthor. Further, we thank Dr. Damon
Kyllo who did a great job in designing the cover picture and Mr. Christian
Ziegler for permission to publish some of his excellent photographs. Techni
cal and administrative help in Germany was provided by Doris Faltenbacher
Werner, Elke Furlkröger, Evelyn Hatzung, Ursula Herlth, Monika Noak, Chris
tine Schlüter, and Dr. Hans Zellner. The project was funded by the Deutsche
Forschungsgemeinschaft (SFB 251; Ökologie, Physiologie und Biochemie
Preface IX
pflanzlicher und tierischer Leistung unter Streß, University of Würzburg).
Last, but not least, we would like to express our gratitude to Dr. Otto Ludwig
Lange for inviting us to publish this mono graph in the Ecological Studies
Series and for his continuous and stimulating support during the preparation
of the manuscript.
September 2002 The Authors
Contents
1 About This Book 1
2 The Natural History of Leaf-Cutting Ants 5
2.1 The Significance of Sodal Insects .... . 5
2.2 The Fungus Growers ........... . 7
2.3 The Natural History of the Leaf-Cutting Ants
of the Genus Atta ........ . 9
2.3.1 Colony Foundation in Atta . . . . . . 9
2.3.2 Division of Labor in Atta Colonies 14
2.3.3 The Maintenance of Fungal Hygiene 17
2.3.4 Communication and Foraging in Atta Colonies 20
2.3.5 Leaf-Cutting Behavior and Load-Size Determination 24
2.3.6 Communication Between the Fungus Garden
and Workers in Atta Colonies ................ . 28
Color Plates 1-16 . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 31
3 The Study Area - Barro Colorado Island ........... 49
3.1 Location and History 49
3.2 Geology and Soils .. 51
3.3 Climatic Conditions . 51
3.4 Vegetation Structure and Composition 52
3.5 Fauna ........ 53
...........
3.6 Research Locations 54
XII Contents
4 Species Composition of the Forest 55
4.1 Selection and Setup of the Study Plot 5S
4.2 Vegetation Inventory ........ . S6
4.3 Abundances and Diversity of Tree Species 57
5 Forest Light Regimes ................. . 61
5.1 Seasonal and Spatial Light Patterns in the Understory 61
5.1.1 Measuring Irradiance . . . . . . . . . 61
5.1.2 Horizontal Distribution of Irradiance 63
5.1.3 Seasonal Aspects ........ . 64
5.2 Vertical Light Variability .... . 66
5.2.1 Measuring Vertical Light Profiles 66
5.2.2 Vertical Distribution of Light 67
6 Canopy Structure of the Forest 71
6.1 Theory ............. . 71
6.2 Measuring LAI and Foliage Orientation 72
6.3 Vertical Distribution of Foliage Angles 73
6.4 Spatial and Temporal Characteristics of LAI Distribution 74
6.4.1 Vertical LAI Distribution . . . . . . . . . . . . . . . 74
6.4.2 Horizontal LAI Distribution and Seasonal Variation 77
6.5 LAI Measurements with the Li-Cor LAI-2000 .. 80
6.6 Comparison of the Study Plot with Other Parts
of the BCI Forest ................ . 81
7 Colony Dynamics ......... . . . . . . . . . . . . . . . 83
7.1 Colony Distribution and Density 84
7.2 Colony Movements 88
7.3 Nest Size 89
7.4 Nest Trees 90
8 Harvest Dynamics 91
8.1 Annual Pattern of Foraging Activity 91
8.1.1 Measuring Foraging Activity . . . . 91