Perspec'vesonBiodiversityThroughTime:Trends,Mechanisms,Constraints

RichardK.BambachResearchAssociate,DepartmentofPaleobiology,

Na'onalMuseumofNaturalHistory,SmithsonianIns'tu'on

Associate,HarvardHerbariaHarvardUniversity

ProfessorEmeritusofPaleontologyVirginiaTech

“Seilacher’sTriangle”ofdeterminantsofphenotype

(Featuresrelatedtothestructuralmaterialsused,suchashardnessandsolubilityof

calciteoraragonite,diffusionratesinprotoplasm,shearstrengthofmuscleandcar'lage.)

(Featuresdeterminedbyinheriteddevelopmentalprogram,

suchaslackofmouthpartsintrilobites,presenceofdorsalnervechordinchordates,

testofopalinesilicaindiatoms)

(Featuresdeterminedbytheopera'onofnaturalselec'on.)

ConstraintsImposedbyEstablishedFeatures

SourceofOpportunitytoDiversify

Evolu'onhasconstraints

aswellasopportuni'es

(Seilacher1970Lethaia3:393–396)

FigurefromRossandAllmon1990CausesofEvolu5on:APaleontologicalPerspec5ve

KnollandBambach2000DeepTime(Paleobiology26:Supplementto#4)

Difficultyinclimbinglimi'ng“rightwalls”aresetbyphylogene'candmorphogene'cconstraints, makingtheachievementofeachstepuptothenext“megatrajectory”andbiodiversitylevelachanceevent.

Naturalselec'onandisola'onofpopula'onsshouldcombinetodiversifylifefullywithineach“megatrajectory”as'mepasses.

Thissequence(andthatofMaynardSmithandSzathmáry1995)islogicallydeterminis'c.Ifthe“tapeoflife”weretoberunagain(hereorelsewhere),thissequencewouldbeexpected.

Tolifeasweknowit

Prokaryotediversifica'onUnicellulareukaryote

diversifica'onAqua'cmul'‐cellular.

Invadeland Int.&Tech.

“Wai'ngTime”toeach

breakthrough

Detailedstudyofdiversityisavailableforonlythelast550Myr

Jack Sepkoski’s original “three fauna” figure, used in his talk at the Geological Society of America Meeting in 1980

The iconic illustration of paleobiodiversity — Sepkoski’s Family Diversity graph

Sepkoski1981Paleobiology7:36–53

Alroy2010Science329:1191–1194MarshallScience329:1156–7

ThePBDBiss'll

addingdataand

refiningitsmethodology

PBDB2008

PBDB2010

Sepk.Genera2002

Despitedifferences

acommonsignalpajern

isemerging

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MarineGenusDiversityPlojedbySubstage

UsingAllGeneraandInterpola'ngEndPointsofLessWellResolvedGenera

Cambrian Explosion

Ordovician Radiation

Mid-Cretaceous through

Cenozoic Radiation

Butremember,thisisjustthe“Aqua'cMul'cellular”“megatrajectory”

Thefirstordersignal,diversityincrease,isfromtheradia'onofthethree“evolu'onaryfaunas”

Habitattype Pro'sts Plants Fungi Animals

Terrestrial(dryland) 6 2 5

Terrestrial(moisthabitats,soils) 13 9 5 10

Freshwater 24 2 5 15

Marine 26 1 3 34

Livinginadry,low‐humidityenvironmentexposedtotheatmosphereisextremelydifficult.Fewhighertaxahavemadethetransi'onfully.

Climbingthat“rightwall”ofexposurewasfarharderthandealingwithosmo'cissuesinfreshwater.

Thenumberofphylawithrepresenta'veslivingfreelyindifferenthabitatsemngs.

DatatabulatedfromMargulisandChapman1998KingdomsandDomains: AnIllustratedGuidetothePhylaofLifeonEarth

Anexampleofthedifficultyof“climbingarightwall” Notallhigherphylaarecapableofdealingwithterrestrialenvironments

Total

13

37

46

64

Ofthees'mated1,750,000describedspecies,about250,000aremarineand1,500,000areterrestrial.

(Groombridge&Jenkins2002WorldAtlasofBiodiversity)

FAMILYdiversity(GraphsfromBenton2001Geol.Jour.36:211–230)

Butinvasionofthelandcreatedvastnewopportuni'esfordiversifica'onatlowertaxonomiclevels

Easeofgeographicisola'onplusmutualis'cinterdependences,suchasthoseforfeedingandreproduc'onbetweenangiospermsandarthropods,plusparasi'cspecializa'onshaveledtoexcep'onallyhighterrestrialspeciesdiversitydespitetherestricteddiversityofhighertaxa.

Halftoonequarterthenumberofphylaonland,butmorefamiliesthanintheoceans.

Whataboutperturba'onstobiodiversity

onaglobalscale?

Global diversity throughout the next temporal interval was reduced after fifteen of the eighteen Mass Extinctions. In these events origination was able to replace lost diversity

during the next interval only three times.

Thedeeperques'oniscausa'on.Wehavesomegeneralunderstandingofthethreebiggest—(end‐Ord,end‐Perm,end‐Cret)butevenforthosewedonotknowenough.Forallwes5llneedmorereliabledetailsabout5ming,selec5vity,geographicpaNern,andenvironmentalseOngs.

End‐OrdEnd‐Perm

End‐Cret

Fr/Fa

End‐Tri

Eighteensubstageshavepeaksofbothmagnitudeandrateofex'nc'onineachofthreedifferentstylesofevalua'ngtheSepkoskigenusdata.Thesecomprisethefullsetofunambiguousmassex'nc'onevents.

ADiversityofMassEx'nc'ons

Bambach2006AnnualReviewofEarthandPlanetarySciences34:127–155

The“BigFive”MassEx'nc'onsaretheONLYintervalsinwhichmarinegenusdiversitydecreased

bymorethan20percent.

Bambachetal.2004Paleobiology30:522–542

PBDB‐DashedlineR&M(Sep)‐SolidlineFR2‐Dojedline

Shading–Decreasingphase

X–ex'nc'onevent(Barnesetal.1996)

Evenlydistributedinincreasinganddecreasingphases

• –MassEx'nc'on(Bambach2006)

Clusterindecreasingdiversityphases(P=0.03)

X–non‐massex'nc'onsarepreferen'allyinincreasingdiversityphases

The62Myrperiodicitytothe

fluctua'onofdiversity

isubiquitousinglobaldata

MelojandBambach2011Paleobiology37:383–408

SLGdiversityfluctua'on(solidlineanddots)isan5phaseto87Sr/86Srra'ofluctua'on(dashedline)

Melojetal.2012Jour.Geol.120:217–226

The62Myrperiodicityinbiodiversityalsocorrelateswith aperiodicityinthenumberofmarinesedimentaryforma'ons.

Togetherthesesuggestthattheperiodicityinbiodiversity mayberelatedtoatectonicpajernsthatcanaffectendemicfaunas.

Thesepajernsmaybemoreregularin'mingthanpreviouslythought.

Marineanimaldiversityfluctua'onalsocorrelateswithseveralgeologicalphenomena

Globalbiodiversityisthesumofthediversityofallthetaxonomicgroupspresent.

Whatarethecontrolsondiversityanddiversitychangewithingroups?

Origina'onEx'nc'on

Time

Diversity

Diversitywithinagroupiscontrolledbytheinterac'onoforigina'onandex'nc'on

O E

MaxDiv

Priortoreachingmaximumdiversityorigina'onmustaveragemorethanex'nc'on

Axerreachingmaximumdiversityorigina'onmustaverage

lessthanex'nc'on

26 

3

20 

2

6 1 19  25 

Origina'onandEx'nc'onTrendsfor51Ex'nctHigherTaxaDatafromfirstandlastintervalsomijedtoeliminate“smallnumber”enhancedpropor'ons.

GilinskyandBambach1987Paleobiology13:427–445

Origina'ondecreases,butex'nc'ondoesnothaveapreferredtrend.

E O 

The20holophyle'cgroupsanalyzedhadexactlythesamepajernastheparaphyle'cgroups.

GilinskyandBambach1986Paleobiology12:251–268

Whatcanbelearnedfromthediversityhistoryofindividualgroups?

*x

Only3of17groupshadtheircenterofgravityvarysignificantlyfromthemeanof1,000bootstrapsimula'onsofeachrelevantgroup, butthedistribu'onofvaria'onaboutthemeanwasnotsymmetrical, aswouldbeexpectedifthegroupswereactuallystochas'cphenomena.

Thecenterofgravityof14of17groupsoccurredearlierthanthemeanofthesimula'ons.

Theprobabilityofthatdistribu'onisjust0.006.

Noneofthe17groupshadamaximumdiversitysignificantlydifferentthanthemeanof1,000bootstrapsimula'onsoftherelevantgroup, butthedistribu'onofvaria'onaboutthemeanwasnotsymmetrical, aswouldbeexpectedifthehistorieswereactuallyallstochas'cphenomena.

Maximumdiversityof15of17groupswashigherthanthemeanofthesimula'ons.

Theprobabilityofthatdistribu'onisjust0.001.

GilinskyandBambach1986Paleobiology12:251–268

Generalpajernsofcladeevolu'onarydynamics:

Origina'ongenerallydecreasesoverthehistoryofagroup.

Ex'nc'onhasnoregulartrend.Itdoesnottendtoeitherincreaseordecrease.

Thediversityhistoryofagroupisgenerallynotsta's'callysignificantlydifferent fromthemeanof1,000bootstrapsimula'onsofthesamedura'on.

Nonetheless,thecenterofgravityofarealgroupisgenerallyearlierin5me andthemaximumdiversityofarealgroupisgenerallygreater thanthemeanvaluesfor1,000bootstrapsimula'onsofthatgroup’shistory.

Despitethenearstochas'cdiversityhistoryofindividualgroups, thereissta's'calevidencethatthetypicalearlyhighleveloforigina'on doesproducemorediversitythanwouldbeexpectedfromchancealone.

Neitherorigina'onorex'nc'onisdiversitydependent atleastwherewithingroupdiversityisconcerned.

RESEARCH AGENDA:Whydoesorigina'ondecreaseover'mewithinagroup?Isitan“aging”ofthegenome?Orisitacompe''veissueasotherevolvingtaxacapture moreoftheavailableecospaceformerlyopentothegroupbeingexamined, thusinhibi'ngsuccessfulorigina'oninthegroupofinterest?Thesecondpossibilitymayexplainwhyincumbentssurvive,butorigina'ondecreases.

Whataboutecologicaldiversity?

The Ecospace Cube Exploded:

6 x 6 x 6 = 216 Possible

Modes of Life

Bambachetal.2007Palaeontology50:1–22

ATheore'calModelofEcospace

Early‐MidCambrianonly

12 19 30 62

Ecosystemcomplexityincreasedwiththeincreaseinthenumberofu'lizedmodesoflifethroughthePhanerozoic

Addmodesatall'ers: morepredators, moremo'lity, moreinfauna

Bambachetal.2007Palaeontology50:1–22

BetweentheDevonianandtheNeogenewithincommunitydiversityincreased

anduseofecospacewithincommuni'es

alsoincreased.

Localecosystemshavebecomemorecomplexascommunitydiversityhasincreased.

Thesechangesareamongthelikelysourcesforobservedsimilarglobalchanges.

Whataboutthediversityatthelocallevel?

BushandBambach2004JournalofGeology112:625–642

Averagegenusalphadiversity

rarefiedto200specimens

Genusdiversity

infossil

assemblagesincreased

byasmuchasafactorofthree

betweenthemid‐Paleozoic

andtheLateCenozoic.

Diversitywithinpaleocommuni'es(untransported

fossilassemblages)hasincreased.

Threetrendsinecosystemstructure:Increasedpreda'on,Increasedmo'lity,Increased

Infaunaliza'onareexpressed

fromthecommunityleveltothegloballevel.

Bushetal.2007Palaeobiology33:76–97

Within‐communityuseofecospace

hasalsoincreased.

Pajernsofdiversitychangeandecosystemchange

atindividualgroupandcommunitylevelsmustbeintegratedtogetherifwearetounderstandhowgroupsinteract

andhowfaunalsuccessioninfluencesdiversity.

The history of diversity on earth has not been a single unified process. Each group has had its own diversity history.

Bambach 1983 after Sepkoski 1981

Thecontextinwhichtheevolu'onofanygroupoccurschangesas

othergroupswaxandwane.

BushandBambach2011AnnualReviewofEarthandPlanetarySciences39:241–269

Usingclusteranalysisbasedonamixofclasses,subclassesandorders,

ratherthanjustclassesasSepkoskidid,thehistoryoffaunalsuccession

inthemarinerealmbecomesthesuccessionoftwelve,notjustthree,evolu'onaryfaunas.

RESEARCHAGENDA:

Whyshouldsomanygroupshave“co‐ordinated”histories?

Howdoesecologicalinterac'onaffectthefateofthesesuitesoftaxa?

Isthisthelevelatwhichtheever‐presentfailureoforigina'onwithingroupsisbeingproduced?

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PropExt  Overallex'nc'ondecreaseswith'meeventhough

withingroupsithasnotrend.Thisisbecausetaxonsor'ngon

evolu'onaryvola'lityhasremovedhighex'nc'onrategroups.

Origina'onmaydecreaseoverallinpartbecauseofincreasingdiversity,

notbecauseorigina'onwithinindividualgroupsdecreases.Ineffect,

ini'alorigina'onmayremainaboutconstantoverall,butasdiversityincreasesnewtaxabecomeasmaller

por'onofthetotalfauna.

Propor:on of Ex:nc:on by Substage 

Propor:on of Origina:on by Substage 

Time

Time

Controls,opportuni'es,andconstraintsonbiodiversity includebothgeologicalinfluencesandbio'cinfluences.

Adap'veradia'onispartoftheearlyhistoryofmostgroups, butchanceandphysicaleventsalsoaffectdiversitytrajectories somostdiversityhistoriesvaryonlyslightlyfromstochas'chistories.

Taxonomicsuccessioncauseschangeinecologicalcontext andeachgroupmusteitheraccommodateorfadeaway.

Foranyestablishedgroupevolu'oninothergroupstendstoleadtocompe'tors. Thismaybethesourceoftheuniversaldecreaseinorigina'on withnormalajri'oncausingdeclineindiversitytoeventualex'nc'on.

Thegeneralsuccessionofmajorevolu'onarytransi'ons shouldbesimilaranywherelifehasdiversifiedextensively.

However,thechancesofmakingthemajortransi'onsaresmall, thus“pondscum”willprobablybeencounteredfarmoreoxen thanthingslikeac'velargelandanimals.

Aplanetwithdiverselifeformsmusthaveregular,butnotexcessive, environmentalchangetocon'nuouslys'mulateevolu'onarychange.

ScotesePALEOMAPProject

TheEarth

ChangesAllTheTime

Finis