Theeffectofsoil-bornepathogensdependsontheabundanceofhosttreespecies

YuLIU

SYSU-AlbertaJointLabforBiodiversityConservation,SunYat-senUniversity

Oct11st,2016Beijing

Innature,thevastmajorityoftreespeciesare

rarespecies.

100

80

Frequency

60

40

20

0

30.1%ofall236treespecies(abundance≤50stems

followingHubbell’scriterionfordefiningrarespecies)

0500010000150002000025000

Speciesabundanceofthe50haHeishidingplot

Howarerarespeciesmaintainedin

ecologicalcommunities?

2

Introduction

●Amongothers,stabilizationmechanisms,asthedefiningfeatureofstablecoexistence,areessential.

Percapitagrowthrateofapopulationshouldbeadecreasingfunctionofabundancesothataspeciesisabletoincreaseatlowabundance(i.e.,

fitnessadvantageatlowdensity),whichformsthebasisoftheinvasibilitycriterioncriticalforstablecoexistence(Chesson2000;Siepieski&McPeek2010).

Chesson(2000)Annu.Rev.Ecol.Syst.31:343-366;Siepielski&McPeek(2010)Ecology91:3153-3164.

3

Introduction

●Thedecreasingfunctionofabundancealsoimpliesdisadvantageathighdensity.

Fromtheperspectiveofanindividualspeciesasnegativedensitydependence(NDD).

Stabilizingnichedifferencesbetweenspeciesinacommunity(Chesson2000),referredtoasacommunitycompensatorytrend(CCT;

Connelletal.1984).

Connelletal.(1984)Ecol.Monograph.54:141-164;Chesson(2000)Annu.Rev.Ecol.Syst.31:343-366.

4

Introduction

●ControversyarisesaboutthestrengthofNDDinrare

speciesversuscommonspecies,whichseemstocontradictthepredictionsoftheCCT.

A

ymmetricDen

hape

ecie

A

TreeC

Tr

OPICIOm

a

Negativeplant-soilfeedbackpredictstree-speciesrelativeabundanceinatropicalforest

scottA.ManganL2,stefanA.schnitzer,2,EdwardA.Herre2,keenanM.L.Mack3,MarianaC.valencia4,Evelyn1.sanchez2&JamesD.Bever3

Lizas.comita,2xHeleneC.Muller-anau2,3aonuar3een.Ue3,4

Thefactorsdeterminingspeciescommonnessanrarareoorunerso0,arcuarn

diversecommunities.Theorypredictsthaneraconsneorsoesaeconseccanoer

(heterospecific)speciescaninfluenceaseces'reaveaunance,uercaessareacin.usingahierarchicalmodelofsurvivalororean,seensorocareesecies

onBarrocoloradoIsland,panama,weeseeerseces'sensVOneornnVUasrelatestotheirrelativeabundanceinecoun.eounevaraonaonsecesne

effectofconspecific,butnotheterospecc,neorsonsurvva,aneounasincan

relationshipbetweenthestrengthofconsecicneioreecsansecesaunance.ecca,rarespeciessufferedmorefromthepresenceoconsecicneorsancoonsecies,

suggestingthatconspecificdensitydeenencesaesseciesaunancesnverseCounes.

conspecificNegativeDensity

DependenceandForestDiversity

DanielJ.Johnson,*wesleyT.Beaulieu,JamesD.Bever,keithclay

conspecificnegativedensity-dependentestablishment,inwhichlocalabundancenegativelyaffectsestablishmentofconspecificseedlingsthroughhost-specificenemies,caninfluencespecies

diversityofplantcommunities,butthegeneralityofthisprocessisnotwellunderstood.wetestedthestrengthofdensitydependenceusingtheunitedstatesForestservice'sForestInventory

andAnalysisdatabasecontaining151speciesfrommorethan200,000forestplotsspanning

4,000,000squarekilometers.wefoundthatmostspeciesexperiencedconspecificnegativedensitydependence(CNDD),buttherewaslittleeffectofheterospecificdensity.Additionally,abundantspeciesexhibitedweakerCNDDthanrarerspecies,andspecies-richregionsexhibitedstronger

CNDDthanspecies-poorregions.collectively,ourresultsprovideevidencethatCNDDisa

5

Introduction

●ForatrueunderstandingoftheroleofNDD,well-designedexperimentsonthemechanismsregulatingNDDareneeded.

●TheJanzen-Connellmechanism(JC;Janzen,1970;Connell,1971),oneofthemajorNDD,hasbeenprovedbyanincreasing

numberofstudies(e.g.,Packer&Clay,2000;Belletal.,2006;Liuetal.,2012;Bagchietal.,2014).

I:Numberofseedsperunitarea

P:Probabilitythatseedorseedlingwillescapefromnaturalenemies

PRC:Populationrecruitmentcurve

Beinghost-specificanddispersal-limited,soilpathogensarekey

agentsfortheJCmechanism.

Janzen(1970)Am.Nat.104:501-528;Connell(1971)InDynamicsofPopulations;Packer&Clay(2000)Nature404:278-281;Belletal.(2006)Ecol.Lett.9:569-574;Liuetal.(2012)J.Ecol.100:1019-1028;Bagchietal.(2014)Nature506:85-886

Introduction

●Studysiteandspecies:HeishidingNatureReservein

Guangdong,naturallyoccurringcontrastsinabundanceofatreespeciesOrmosiaglaberrima(Liuetal.2015).

●Aim:totestwhethertheJCmechanismissensitivetoadultdensityonalargerscale,notmerelyinthevicinityofa

parenttreeofagivenseedling.

Table3IPopulationstructures(byDBHClasses)of0,glaberrimatreesinthethreeabundantpopulations(A1-A3)andthethreerarepopulations(R1-R3).

Abundance

population

Juvenile(DBH:1-9cm)

premature(10-25cm)

Mature(>25cm)

Abundant

A1

32

14

26

A2

20

30

A3

36

15

22

Lowdensity

R1

R2

R3

7

Liuetal.(2015)Nat.Commun6:10017

High-densitysites

8-12m12-20m

0-4m

4-8m

25

20

15

10

5

0

25

Results_fieldsurveyforseedlingdensity

Ratioofseedlingdensity

1.2

1.0

0.8

Numberofseedlingsperm2

0.6

0.4

OctDec

Low-densitysites

Aug

8-12m12-20m

Apr

Jun

0.2

0-4m

4-8m

0

AprJunAugOctDec

Observationtime

20

15

10

5

0

Densitiesofsurvivingseedlingsatdifferentdistancesfrom

Oct

Aug

Apr

Jun

Dec

adulttreesfareddifferentlyinabundantandlow-densitysites.

Observationtime

8

Liuetal.(2015)Nat.Commun6:10017

Results_distanceeffectonseedlingsurvival

High-densitysites

00.20.40.60.81.000.20.40.60.81.0

Insoilcollectedfromabundantsites,

seedlingsurvivalsignificantlyincreased

Seedlingsurvivalrate

withincreasingdistancefromfocaltrees.

NofungicidesFungicides

05101520

Low-densitysites

Therewasnosuchtrendinsoilcollectedfromlow-densitysites.

NofungicidesFungicides

05101520

Distance(m)

Bluecolor(solidline)foruntreatedsoil

Redcolor(dashedline)forfungicide-treatedsoil

Liuetal.(2015)Nat.Commun6:10017

9

Results_GLMMformodelingseedlingsurvival

Intercept

Abundance·DensityDistance·

Fungicide

Seedprovenance

Abundance×Distance

Seedlingsurvivalwas

positivelyassociatedwith

distanceattheabundantsites(3-wayinteraction:z=5.06,

Abundance×Fungicide。

Density×Fungicide

Distance×Fungicide

Fungicide×SeedprovenanceAbundance×Distance×Fungicide

·IIIIIII

-3-2-1012345

Estimate±1.96SE

10

Liuetal.(2015)Nat.Commun6:10017

Results_dilutiontreatment

Seedlingsurvivalrate

Fungicide

1.0

0.8

Aftertheproportionofuntreatedsoil

<10%,therewouldbenolongereffectofinoculation(at5%untreatedsoil,P=0.30)

0.6

0.4

0.2

Seedlingsurvivalincreasedwiththe

Nofungicide

reducingproportionofuntreatedsoil.

0.0

1009080706050403020100

Theproportionofuntreatedsoil(%)

11

Liuetal.(2015)Nat.Commun6:10017

Results_Pathogenisolation

2cm2cm

Seedlinmgotliyaate

1.0

Highhostspecificity

RottenseedDamping-offseedling

0.8

0.6

0.4

0.2

0.0

SocCcoCfaOgl

Fusariumoxysporum

Treespecies

12

Summary

●F.oxysporumsuppressedseedlingrecruitmentofO.glaberrimaatabundantsites(high-densitydisadvantage).

Preventindividualspeciesfromoverwhelmingotherspecies,andthuspromotespeciesdiversityinacommunityasassumedbytheJC

mechanism.

●Therewaslittleeffectofthepathogenonseedlingsatlow-densitysites(low-densityadvantage).

Promoteaspeciestoincreaseitspopulationatlowabundance.

●DifferentiatedstrengthoftheJCeffectontwospatialscalesforaspeciesisaprerequisiteoftheCCT.

DonotsupportstrongerNDDforrarespecies.

Liuetal.(2015)Nat.Commun6:10017

13

Perspectiveofthisstudy

●Akintotheincreasingnegativefeedbackoninvasivespecieswithitsinvasionhistoryprolonging(e.g.,Diezetal.,2010;Dostáletal.,2013),theJCeffectononespeciescanbepredictedtovarytemporallyduetopathogensaccumulatingarounditovertime(Liuetal.,tobesubmitted).

Plantpopulationdynamic

Soilfeedback

Positivefeedback

Plantpopulationsize

Netfeedback

ABC

Negativefeedback

Balancedstage

IncipientstageEstablishingstage

Establishmenttime

14

Diezetal.(2010)Ecol.Lett.13:803-809;Dostáletal.(2013)Ecol.Lett.16:1277-1284

Perspectiveofthisstudy

●TheJCeffect,measuredbyinhibitionofpathogensonseedlings(i.e.,severityofplantdiseases),shouldbecontext-

dependentwithintheframeworkofthediseasetriangle(Francl,2001).

Uniquetophytopathologyandwelldocumentedinagriculturalsystems,butlimitedrecognitionamongecologists.

(Localadaption)

Disease

Susceptibility

(Localadaption)

Genotype

LightintensityHumidity

Exudate

Developmentstage

Ifignoringthecontext,therewillbenosurpriseforthemixed

resultsoftheJCeffectevenonthesamespecies.

15

Francl(2001)ThePlantHealthInstructor;Liuetal.tobesubmitted

Perspectiveofthisstudy

●Astothesamelow-densitysiteofO.glaberrima(Liuetal.2015),onelatterstudy(maybeignoringexperimentalcontext)seemedtoobtainthecontrastingresult.

Table3IPopulationstructures(byDBHClasrarepopulations(R1-R3).

ses)of0.glaberrimatrees

inthethreeabundantpopulation

s(A1-A3)andthethree

Abundance

population

Juvenile(DBH:1-9cm)

premature(10-25cm)

Mature(>25cm)

Abundant

A13214