Table Of ContentPillars of Evolution
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Pillars of Evolution
Fundamental principles of the
eco-evolutionary process
DOUGLAS W. MORRIS
ProfessorofBiologyandLakeheadUniversityResearch
ChairinNorthernStudies,LakeheadUniversity,Canada
PER LUNDBERG
ProfessorofTheoreticalEcology,DepartmentofBiology,
EcologyBuilding,LundUniversity,Sweden
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Preface
Sixyearsago,inthisveryroomandinthegoodcompanyoffriendsandstudents,we
shared the kernel of an idea. ‘Wouldn’t it be grand’, we mused, ‘to write a book that
transforms the way that we and others think about the union between evolution and
ecology’.SobeganourpersonalodysseytowardthePillarsofEvolution.
What we call and understand as evolution by natural selection depends only on its
threepostulates,eachofwhichisarepeatedlyverifiedfact.Whereverthosefactsapply,
so too does adaptive evolution. Life is self-replicating with error. More offspring are
produced than can survive. The survival of (future) offspring depends on heritable
charactersthateffectdemography.
Thus, the fabric of life, with its interwoven patterns and textures, emerges only
through evolution. Biology is a subset of evolution, not the other way around. Our
intent is to take this message to senior undergraduates and graduate students while
theyaredevelopingtheirworldview.Butwealsoattemptastyleandcontentthatmakes
ourbookattractivetopractisingscientistswhomaybeprovokedtofollow,orchallenge,
ourapproach.
We take no credit for the majority of ideas covered in this book. Indeed, they have
beenshapedandhonedovermanyenjoyablehourscontemplatinglifewithfriendsand
colleagues.Wehavespacetonamebutafewofthemostinfluentialandinspiring:Joel
Brown, Robert Holt, and Jo¨rgen Ripa. Kelly Morris and Lena Lundberg Magnusson
made it possible for us to write with heart, and not just a scientist’s impartial mind.
The ideas in our little book were improved by the comments from sage and sincere
anonymousreviewers,andthroughthewisecounselofIanShermanandHelenEaton.
We are thankful for the financial support provided to DWM by Canada’s Natural
SciencesandEngineeringResearchCouncil,andtoPLbytheSwedishResearchCoun-
cil.Mostofall,wearegratefulfortheopportunitytoshareourideasandperspectives
on a discipline that we consider more important than any other. We believe that our
approachtothoseideasissomewhatunique,andthatithopefullyhassomepotential
to alter the ways that future scientists understand, study, and teach biology. We are
saddened that the shortness of human lifetimes will let us see but a tiny fragment of
thatfuture.Butweareheartenedthat,becauseofevolution,wecanvisualizepossible
future worlds, and savour, surreptitiously, the ways that our descendants may enjoy
them.
Ourtextbeginswith‘Imagine...’.Yes,imagine!
KakabekaFalls,Canada
AllHallow’sEve2010
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Contents
1. Introduction 1
Whystudyevolution? 1
Themapofevolution 3
Pillarsofevolution 5
2. Mechanics 13
Overview 13
Introduction:thescaleofmechanism 14
Randomchange 15
Systematicchange 19
Quantitativeinheritance:afullunderstandingofmechanicsmustinclude
anassessmentofpolygenictraits 27
Interactionsamonggenesandtraits:trade-offsandconstraintsshackle
adaptiveevolution 31
Plasticity:malleableresponsesareadaptivesolutionstovaryingenvironments 34
Achallengetothegeneticaltheoryofadaptiveevolution:can
developmentalandbehaviouralplasticityforcegenestofollowtraits? 40
Mechanicsofpopulationgrowthanddecline 48
Thelimitsofmechanics:mechanics,thoughessential,isaninsufficient
explanationforevolution 49
Reflection 50
3. Function 53
Overview 53
Introduction:wheretraitsmeettheenvironment 54
Thefitness-mappingfunction 60
Fitnesssetsandthefitness-generatingfunction 62
Theadaptivefunction 66
Mappings 75
Multipletraits 80
Optimaltraitvalues 83
Reflection 86
4. Structure 89
Overview 89
Introduction:mappingtraitsontofitness 90
Traitsandfunction 91
viii Contents
Traits,states,andstrategies 98
Optimization 103
Constraintsandreinforcement 111
Structureatdifferentscales 116
Thestructurematrix 118
Wheretraitsfailtomapontofunction 133
Reflection 135
5. Scale 137
Overview 137
Introduction:backward-lookingadaptation 138
Shortcutsinmodellingevolution 142
Sizeandallometry 144
Grain:howthescaleofenvironmentinfluencesevolution 146
Multi-leveladaptation 167
Prescriptions:avoidingthefallaciesofsimplicityandcomplexity 172
Reflection 176
6. Dynamics 179
Overview 179
Introduction 180
Growthanddecline 182
Densitydependenceanddemography 183
AdaptivedynamicsandtheG-function 187
Theadaptivelandscape 191
Evolutionarybranching 194
RedQueendynamics 198
Spatialdynamics 200
Bet-hedging 203
Trophicinteractions 206
Reflection 214
7. Adaptation 217
Overview 217
Introduction:explanationsforlife 218
Thepossible,theephemeral,andthefeasible 238
Epiphenomena:wherearethetrees? 241
Maladaptation:lostexpectationsorpromisedsuccess? 244
Reflection:thethreadofevolution 247
References 249
Index 265
1
Introduction
A WORLDVIEW
Why study evolution?
Imaginethatyouarewalkingthroughyourfavouritewoodland.Perhapsyouvisualize
treesofdifferentformsandtypes.Somearetall,someshort.Somehavesmoothbark,
some rough. Some have large single leaves, others compound. Perhaps you imagine
songbirds flitting about in the shrubs. They serenade you with song. Their iridescent
plumagesparklesasitcatchesashaftofyellowlightgentlyfilteredthroughapatchwork
of fluttering foliage. Others, cloaked shabbily in tattered feathers, scratch in the litter
nearyourfeet.Perhapsyouseeyourselfstoopingtopeerintentlyintothegolden,ivory,
or indigo corolla of a wildflower. You inhale its fragrant perfume. You marvel at bees
hovering,momentarily,besideoneinflorescencebeforebuzzingtothenext.Youpause,
lookup,andlikeadesertgazelleslakingitsthirst,drinkdeeplyfromthediversitythat
flowsaroundyou.Lifeembracesyoulikeanoldandcherishedfriend.
‘Evolutionistheultimatefield-guidetobiodiversity’
Youarenotalone.Allnaturalistsareenthralledwithlife,whichfromsharedandhumble
beginningsyieldssuchsplendour,diversity,andsuperbfitbetweenformandfunction.
Weknowthatall ofthese featuresareproductsofevolution. Descendantsdiffer from
theirancestors.Nomatterhowlargeorsmallthedifference,itiscausedbyprocesses
thatlinkonegenerationtothenext.
‘Evolutionexplainshumanoriginsandportendsourcollectivefuture’
Humancultureandreligionarecentredonfinding(ordefining)humanity’splaceand
contextinlife,time,andspace.Evolutionprovidesthemostparsimoniousandelegant
answer.Eachyearwecumulateirrevocableevidenceofourprimateorigins.We,likeall
otherspeciesonthisplanet,areaproductofevolution.Noeducatedhumancandeny
that adaptive evolution is as much a part of the human experience as are our great
religions, cultures, literature, and music. That experience, like all of the others, is
deservingofrespectandnurture.Moreover,itisouronlycollectivelong-termsalvation.
