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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
**
**
**
****
****
**
*
*
*
*
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