MUTUALISM: Ants and their Insect Partners

229 Pages·2008·2.37 MB·English

This page intentionally left blank
MUTUALISM: ANTS AND THEIR
INSECT PARTNERS
A mutualism is an interaction between individuals of two different species of
organism in which both benefit from the association. With a focus on mutu-
alisms between ants and aphids, coccids, membracids and lycaenids, this
volumeprovidesadetailedaccountofthemanydifferentfacetsofmutualisms.
Mutualistic interactions not only affect the two partners, but can also have
consequences at higher levels of organization. By linking theory to case
studies, the authors present an integrated account of processes and patterns
ofmutualisticinteractionsatdifferentlevelsoforganization,fromindividuals
to communities to ecosystems. Interactions between ants and their insect
partnersandtheiroutcomesareexplainedfromaresource-based,cost–benefit
perspective. Covering a fascinating and growing subject in modern ecology,
this book will be of interest to community and evolutionary ecologists and
entomologists,atbothresearchandgraduatestudentlevel.
BERNHARD STADLER isaResearchAssociateintheDepartmentofAnimal
EcologyattheUniversityofBayreuth,Germany.
TONY DIXON is Emeritus Professor in the School of Biological Sciences at
the University of East Anglia, UK, and author of two previous books with
Cambridge University Press: Insect Predator–Prey Dynamics (2000), and
InsectHerbivore–HostDynamics(2005).

MUTUALISM
Ants and their Insect Partners
BERNHARD STADLER
BayreuthInstituteforTerrestrialEcosystemResearch,
UniversityofBayreuth,Germany
ANTHONY F.G. DIXON
SchoolofBiologicalSciences,UniversityofEastAnglia,
Norwich,UK
CAMBRIDGEUNIVERSITY PRESS
Cambridge, New York, Melbourne, Madrid, Cape Town, Singapore, São Paulo
Cambridge University Press
The Edinburgh Building, Cambridge CB28RU, UK
Published in the United States of America by Cambridge University Press, New York
www.cambridge.org
Information on this title: www.cambridge.org/9780521860352
© B. Stadler and A. Dixon 2008
This publication is in copyright. Subject to statutory exception and to the provision of
relevant collective licensing agreements, no reproduction of any part may take place
without the written permission of Cambridge University Press.
First published in print format 2008
ISBN-13 978-0-511-39365-5 eBook (EBL)
ISBN-13 978-0-521-86035-2 hardback
Cambridge University Press has no responsibility for the persistence or accuracy of urls
for external or third-party internet websites referred to in this publication, and does not
guarantee that any content on such websites is, or will remain, accurate or appropriate.
Contents
Preface pagevii
1 Thescopeoftheproblem 1
2 Historicalperspective 9
3 Theoriesonmutualism 14
3.1 Theoriesonco-operation 14
3.2 Thepredictions 21
3.3 Models 22
3.3.1 Lotka–Volterratypemodels;functionalresponse
models 24
3.3.2 Life-historymodels 35
3.3.3 Metapopulationmodels 43
4 Mutualismsbetweenantsandtheirpartners 57
4.1 Phylogenyandfeedingecology 57
4.2 Associationsofantswithnectar/honeydewproducingpartners 65
4.2.1 Ants 65
4.2.2 Aphids 67
4.2.3 Coccids 69
4.2.4 Membracids 73
4.2.5 Lycaenids 79
4.3 Emergingpatternsinthedistributionofoutcomes 83
4.3.1 Phylogeny 84
4.3.2 Genetics 85
4.3.3 Ecology 85
5 Aspecialcase:aphidsandants 89
5.1 Featuresassociatedwithantattendance 89
5.2 Cost–benefitperspective 91
5.3 Theeffectsofantsonlife-historycharacteristicsandfitness 98
5.4 Specializationandcoevolution 100
v
vi Contents
6 Multitrophic-levelinteractions 107
6.1 Mutualismwithinaresource-trackingframework 107
6.1.1 Bottom-upandtop-downforces 107
6.1.2 Plantchemicaldefence 112
6.1.3 Hostplantheterogeneity 114
6.2 Populationeffects 118
6.2.1 Seasonaldynamicsanddensitydependence 118
6.3 Dispersal 123
6.4 Communityeffects 133
6.5 Metamutualism 143
6.5.1 Experimentalevidenceformetamutualism 153
6.5.2 Examplesofmultiplemutualisticinteractions 161
6.5.3 Extrafloralnectaries 167
6.5.4 Generalconclusions 171
7 Prospectsandconclusions 175
7.1 Life-historylevel 176
7.2 Populationlevel 177
7.3 Communitylevel 179
7.4 Ecosystemlevel 181
7.5 Conclusions 182
References 184
Speciesindex 212
Subjectindex 215
Preface
Mutualism, a reciprocal beneficial interaction between organisms, involves
ecologicalandevolutionaryprocessesoccurringatseveralscalesoforganiza-
tion. For many decades mutualism was the stepchild of ecology, neglected,
malnourished and not studied theoretically because the prevailing paradigm
was ‘nature red in tooth and claw’. Positive interactions appeared to be both
moredifficulttoacceptontheoreticalgroundsandtotestexperimentallythan
negative interactions. In particular, trying to understand the conditions for
stability and long-term outcome of positive interactions was (and still is) a
great challenge. Now it is appreciated that there exists a continuum in the
interactions between individuals belonging to different species, like ants and
theirinsectpartners,andthisraisesseveralinterestingquestions.Forexample:
* How can the different life histories of ants and their partners be merged so that
interactionsbecomebeneficial?
* Howdoestheabundanceofthepartnersaffectthestrengthoftheseinteractions?
* Whatarethepopulationandcommunityconsequencesofmutualisticrelationships
fortheinteractingpartnersandindirectlyaffectedspecies?
* Domutualisticinteractionsaffectspeciesdiversity?
* Howdoestheenvironmentaffecttheoutcomeandstabilityoftheseassociations?
* Howcanthedifferentpartnersofantscoexistinlocalandregionalcommunities?
* Howcanmutualistspersistinthefaceofexploiters?
Inthisbookweaimtoexplaintheunderlyingmechanismsofthedynamicsof
these associations by adopting a view that is not ant-centred, because the
selection pressures of such associations are likely to affect both partners. As
a consequence, we are more interested in describing the outcome of associa-
tions, which could be either negative or positive, or negative and positive at
different times. Inparticular, westartwith anhistoricalperspectiveof mutu-
alism and the theory of two-species mutualistic interactions. The differences
vii
viii Preface
andsimilaritiesinecologicaltraitsofmembracids,lycaenidsandcoccidswhen
associated with ants and the many associations that have evolved between
aphidsandantsareaddressed.Mutualisticinteractionsnotonlyaffectthetwo
partnersbutcanhaveconsequencesforhigherlevelsoforganization,suchas
communities and ecosystem processes, which are addressed in later chapters.
Finally,theenvironmentalandecosystemproblemsthatarisefrommutualis-
ticinteractions,especiallyincombinationwithalienspecies,areaddressed.
Withregardtothebreadthofthesubject,thebookshouldbeofinterestto
community and evolutionary ecologists, and especially entomologists study-
ingantsandtheirrelationshipswithlepidopteranorhomopteranpartners.In
addition, it provides students at the graduate level with a theoretical and
experimental background to mutualism, which is a fascinating and growing
aspectofecology.
Wegratefullyacknowledgethesupportofthefollowinginstitutions,which
provideduswiththeopportunitytoworkonthiscomplexsubjectbyoffering
theirresourcesintheformofaccesstoliterature,fundsfortravelling,housing
andofficespace.Inparticular,BSwouldliketothanktheHarvardUniversity,
Harvard Forest, for the generous support during a Bullard Fellowship.
Having access to their unmatched literature resources was essential in the
early phase of the project. The University of Bayreuth was his scientific base
formanyyearswhileastudentandscientist,andallowedhimthefreedomto
follow his interests. On a more personal level, Pavel Kindlmann, with unpre-
cedented generosity, provided a refugeand office space at a critical period in
BS’s career. Without his help the book would not have been completed.
AFGD is particularly indebted to Professor Helmut Zwo¨ lfer who initiated
thestudiesresultinginthisbookwhenheinvitedhimtoBayreuthtomeetBS
at the time of writing his Ph.D. thesis, and to the European Science
Foundation for awarding BS the Fellowship that enabled him to visit the
University of East Anglia and initiate the studies into the costs for aphids
associated with mutualism. We are also indebted to BITO¨ K/ University of
Bayreuth for funding several visits of AFGD to Bayreuth, which greatly
facilitatedtheexchangeofideasthatresultedinthisbook.