Table Of ContentEcology and Evolution of Flowers
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Ecology and Evolution
of Flowers
Editedby
L D. H
AWRENCE ARDER
Department of Biological Sciences, University of
Calgary, Calgary, Alberta, Canada T2N 1N4
S C. H. B
PENCER ARRETT
Department of Botany, University of Toronto
Toronto, Ontario, Canada M5S 3B2
1
1
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Ecologyandevolutionofflowers/editedbyLawrenceD.Harder,SpencerC.H.Barrett.
p.cm.
ISBN-13:978–0–19–857086–8(pbk.:alk.paper)
ISBN-10:0–19–857086–4(pbk.:alk.paper)
ISBN-13:978–0–19–857085–1(alk.paper)
ISBN-10:0–19–857085–6(alk.paper)
1.Plants,Floweringof.2.Plantsecology.3.Plants—Evolution.I.Harder,LawrenceD.II.Barrett,
SpencerC.H.
QK830.E262006
575.6—dc22 2006022878
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10 9 8 7 6 5 4 3 2 1
Dedicated to the memory of David G. Lloyd (1937–2006),
natural historian and founder of the modern theory of plant
reproduction
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Preface
The reproductive organs and mating biology of on floral biology1, topics that have attracted
angiosperms exhibit greater variety than those of increased interest include: pollen limitation of seed
any other group of organisms. Flowers and inflor- production; the nature and strength of selection on
escences are also the most diverse structures pro- floral traits; inflorescence function; the relative inci-
duced by angiosperms. Why should organs that dence and consequences of specialization and gen-
serve but one main purpose, reproduction, evolve eralization in plant-pollinator interactions; the
suchmatchlessvariety?Theanswerseemstoliein occurrence, causes and implications of hybridiza-
the interactions of plants with their pollen vectors, tion; the community context of plant reproduction,
which are necessary to overcome the fundamental including the effects of herbivory on floral evolu-
matingproblemconfrontedbyplants,namelytheir tion;andthephylogeneticsandcomparativebiology
immobility.Thesignificanceoftheseinteractionsis of floral adaptation. Moreover, the scale at which
apparent in the observation that most of the someofthesetopicsarenowbeinginvestigatedhas
reproductivediversityoffloweringplantsinvolves expanded beyond the local population to encom-
features that function during pollination and mat- pass a broader geographical context, including
ing. Thus, the search for explanations of this metapopulations and regional assemblages. Given
diversity should logically focus on mating as a the dynamic nature of this discipline, a review of
process and an outcome, its ecological and genetic recentdevelopments seemedtimely, which promp-
context, its consequences for variation in maternal ted ustoorganize this volume.
and paternal success within and between popula- Ecology and Evolution of Flowers includes 18
tions,anditsevolutionwithinspeciesandlineages. chapters written by internationally recognized
Analysisofthefunctionandevolutionofflowers authorities, which both review recent advances in
has changed considerably during recent decades. floral biology and present new results. The chap-
The traditional descriptive, natural-history tersareorganizedintoanintroductorychapterand
approach, which focused almost exclusively on four major sections that consider different aspects
flowersthemselves, is increasinglyaccompaniedby of floral ecology and evolution. The first chapter
conceptually motivated experiments in both the reviews the seminal contributions of David G.
laboratory and field, formal mathematical theory, Lloyd to the strategic analysis of plant reproduc-
geneticanalysis,andstudiesofpollinatorbehaviour. tion. We have chosen to highlight Lloyd’s con-
In addition, the scope of topics considered has tributions, because his penetrating functional
broadened significantly as the long-standing, artifi- analysis, until illness ended his research career in
cial division between ecological studies of pollina- 1993, identified the current research agenda for
tion and genetic studies of mating has eroded, so major areas in plant evolutionary biology. The
that the reproductive biology of plants is fully remaining chapters build on Lloyd’s legacy and
integratedintoevolutionaryecology.Thisexpansion illustrate the ecological function of flowers, the
ofapproachesandperspectivescontinuestoexpose
newquestionsandstimulatereanalysisofenduring 1 Lloyd DG, and Barrett SCH (1996). Floral biology:
questions.Forexample,duringthedecadesincethe studieson floralevolutioninanimal-pollinatedplants.Chap-
publicationofthepreviousgeneralresearchvolume manandHall,NewYork.
vii
viii PREFACE
alternate evolutionary solutions that enable plants for the next phase of research on this intriguing
to reproduce successfully in varied environments, subject.
and the resulting process of adaptive diversifica- Compilation of such a volume requires the
tion. In all cases, we encouraged authors both to involvementandcooperationofmanyparticipants.
provide a synopsis of current knowledge of their We are grateful to numerous individuals who
chosen topic, and to use their own empirical or contributed to the content and production of this
theoretical studies to illustrate current issues and book. First and foremost, we acknowledge the
prospects for future analysis in more detail. essential contributions of the authors, who pro-
The major sections of Ecology and Evolution of vided the necessary content, worked to enhance
Flowers in turn examine functional aspects of floral synergy among chapters, and tolerated the idio-
traits, the ecological influences on reproductive syncrasies of the editors. Second, we greatly
adaptation, the evolutionary ecology of mating and appreciate the continued enthusiasm for this pro-
sexual systems, and the role of floral biology in ject of Ian Sherman (Commissioning Editor, Biol-
angiosperm diversification. The first section, ‘‘Stra- ogy,OxfordUniversityPress)andhisdecisiveness
tegicperspectivesonfloralbiology’’,presentscurrent in moving the volume along. We also thank the
theoretical perspectives on the relations of fitness to many individuals who reviewed individual chap-
reproductive allocation and floral traits and their ters, thereby enhancing the volume as a whole,
implications for floral adaptation and mating-system including: Lynn Adler, Paul Aigner, Scott
evolution.Thesecondsection,‘‘Ecologicalcontextof Armbruster, Camille Barr, Christine Caruso,
floral function and its evolution’’, illustrates that the Andrea Case, Pierre-Olivier Cheptou, Mitch Cru-
evolutionofreproductivestrategiesdoesnotoccurin zan, Marcel Dorken, Tim Holtsford, Linley Jesson,
isolation, but instead depends on population char- Pedro Jordano, Peter Klinkhamer, Josh Kohn,
acteristics and the influences of other species in the Claire Kremen, Elizabeth Lacey, David McCauley,
community that act as mutualists, competitors or DavidMoeller,BillMorris,SallyOtto,Emmanuelle
predators. This section also considers the con- Porcher,ShaneRichards,LorenRieseberg,Ophe´lie
sequences of anthropogenic disturbance for floral Ronce, Satoki Sakai, Doug Schemske, Dan Schoen,
function. The third section, ‘‘Mating strategies and Stacey Smith, John Stinchcombe, James Thomson,
sexual systems’’ considers the functional con- Jana Vamosi, Diego Va´zquez, Arthur Weis, Colin
sequences of the diverse deployment of female and Webb, Steven Weller, and Paul Wilson. The assis-
male organs within flowers and within and among tance of Bill Cole, Chris Eckert, and Matt Routley
plants. This variety in organ deployment contributes was invaluable in facilitating reviews and interac-
to the diverse patterns of mating within plant popu- tion among authors. In addition, Stefanie Gehrig
lations and characterizes the remarkable variety of (Assistant Commissioning Editor, Biology, Oxford
sexual systems in angiosperms. The final section, University Press) aided considerably during the
‘‘Floral diversification’’, examines the genetic oppor- final production of this book. Finally, we thank
tunities and constraints associated with floral adap- Dale Hensley and Suzanne Barrett for tolerating
tationandconsiderstheroleofthisfloralevolutionin our compulsive fascination with flowers and for
speciation, species integrity and lineage diversifica- their forbearance while we were immersed in the
tion. All sections of the volume are supported by a writing and editing of this volume.
glossary to assist readers in understanding relevant Lawrence D. Harder
terminology and concepts of plant reproduction, Calgary
ecology and evolution. Overall, this integrated treat- Spencer C.H. Barrett
ment illustrates current understanding of the role of Toronto
floral function and evolution in the generation of January 2006
angiosperm biodiversityandoffersmanysuggestions
Contents
Listofcontributors xvii
1 David G.Lloydandtheevolutionoffloralbiology:fromnatural
historytostrategic analysis 1
SpencerC.H.BarrettandLawrenceD.Harder
1.1Introduction 1
1.2Biographicalsketch 2
1.3Self-andcross-fertilizationinplants 5
1.3.1Early investigations onmatingsystems 5
1.3.2Integrationofpollinationandmating 6
1.4Genderstrategies 8
1.4.1Early investigations ofplantsexualdiversity 8
1.4.2Theoriesonthe evolutionofsexualsystems 10
1.4.3Genderconcepts andtheory 10
1.5Allocation strategies 11
1.5.1Allocation tocompetingfunctions 12
1.5.2Size-number compromises 13
1.5.3Applicationtospecificproblems 14
1.6Floralmechanisms 14
1.6.1Sexual interference 15
1.6.2The evolutionofheterostyly 15
1.7Lloyd’sevolution 17
References 18
Part1 Strategic perspectives onfloralbiology 23
2 Selection onreproductive characters:conceptual foundationsandtheir
extensiontopollinatorinteractions
MartinT.Morgan 25
2.1Introduction 25
2.2Phenotypic selectiononreproductive strategy 26
2.2.1Phenotypic selectionandevolutionarystablestrategies 26
2.2.2Phenotypic selectionandinheritanceofquantitative characters 27
2.2.3Measuringphenotypic selection 28
2.3Plantandpollinatorinteraction 29
2.3.1Specialist orgeneralist? 30
2.3.2Pollinationastrade 32
2.3.3Ecologicaldynamics 32
2.4Self-fertilization, phenotypic selection, andreproductive assurance 34
ix
