Lectureoutline/goals:÷  Introduc3on

•  Diversity•  Rolesandimpacts

÷ GeneralbiologyI.  Brood(offspring)produc3onII.  Emergence/dispersalIII.  Coloniza3on

BarkbeetlesI

1

Barkbeetles÷  Feedwithinsubcor3cal3ssues(e.g.

phloem)ofvirtuallyallpartsofwoodyandherbaceousplantso  Rootso  Stems/boleso  Branches/twigso  Fruits/cones

÷  Generallymono-tooligophagous÷  “Pest”speciestendtospecialize÷  Mostcommonlyassociatedwith

conifers

Dendroctonus ponderosae Hylurgops porosus Ips pini Pityogenes knechteli Trypodendron lineatum Dendroctonus brevicomis Dendroctonus pseudotsugae Dendroctonus murrayanae Dendroctonus valens Dryocoetes autographus Dryocoetes confusus Gnathotrichus sulcatus Hylastes gracilis Hylastes macer Hylastes nigrinus Hylastes ruber Hylastes reticulatus Hylastes subcostulatus Ips emarginatus Ips latidens Ips mexicanus Ips perturbatus Orthotomicus caelatus Polygraphus rufipennis Pityopthorus spp. Pityokteines ornatus Scierus annectans Scolytus tsugae Scolytus ventralis

500 54

183 379 82

0 1 5 0 4 0 0

13 1 1 2 4 5 2 9 9 1 2 1 1 0 0 2 0

327 106 839 714 48

1 0 0 7

13 1 1 4 5 9 0 0 0 2 1 1 0 1 0

25 1 2 0 3

1995 1996

BarkbeetlescapturedovertwoyearsinalodgepolepinestandinsouthernBC

From:Safranyik,LintonandShore2000 2

Rolesandimpacts

Ecologicalroles:÷ Succession÷ Firecycles÷ Soilnutrientcycles

Socio-economicimpacts:÷ Produc3onforestry(all

aspects)÷ Aesthe3csandthewildland

urbaninterface÷ Biodiversityand

endangeredspecies÷ Waterquan3ty/quality÷ Carbondynamicsandglobal

warming

3

0

2000

4000

6000

8000 Mountain pine beetle (Dendroctonus ponderosae)

Thou

sand

s of h

ecta

res a

ffect

ed

Spruce beetle (Dendroctonus rufipennis)

0

100

200

300

400

Year

Thou

sand

s of h

ecta

res a

ffect

ed

Thou

sand

s of h

ecta

res a

ffect

ed

0

500

1000

1500

2000

2500 Western balsam bark beetle (Drycoetes confusus)

AreaaffectedbysomeprimarybarkbeetlesinBC

Source: CFS, Forest Insect and Disease Survey

4

III.Coloniza3on-  Beetle-treeinterac3ons-  Mortalityfactors

-  Treedefense,compe33on,preda3on

I.Broodproduc3on- Ma3ng- Gallerycon.struc3on- Oviposi3on- Brooddevelopment

II.Emergence/dispersal- Flight-  Hostselec3on-  Environmentalimpacts

-  Temp,humidity,light

Generalbiology

5

I.Broodproduc3on-1

÷  Malesorfemalesini3ateaYacks(dependsonspecies)÷  Maleini3ators=nup3algallery

o  Mul3plefemales(polygamous)o  Egggalleriesextendfromnup3alchambers

÷  Femaleini3ators=ma3ngatbarksurfaceo  Mostspecies+/-monogamous

÷  GallerypaYerns(withhost-treeiden3fica3on)o^encharacteris3cofspecies

Ipspini

Pseudipsmexicanus

Dendroctonusponderosae

Scolytusmul6striatus Pityogeneschalcographus 6

I.Broodproduc3on-2

÷  Females:o  Eggslaidsinglyoringroupsinnichesalongmarginsof

galleryo  Nichespackedwithfrasso  Fecundityfromseveralto300eggs/female

÷  Males:o  Frequentlyassistfemalesbycleaninggallerieso  Adapta3onsforclearingfrass/boringdust:

•  elytraldeclivity,flaYenedheadcapsule,hairiness.

Dendroctonusponderosae

Dendroctonusrufipennis

Ipspinimale

7

I.Broodproduc3on-3÷  Larvaefeedanddevelopthrough

severalinstars÷  Pupa3onoccursinenlargedchambers

attheendoflarvalgalleriesorincommonfeedingarea

÷  Young(i.e.teneral)adultso^enfeedtocompletematura3on(increaseflightmuscles,acquiresymbionts,sclero3ze)

÷  Matureadultscutexitholetooutside÷  Matura3onfeedingmayinvolveother

plantparts(e.g.Europeanelmbarkbeetle)

8

I.Broodproduc3on-4

÷  Thenumberofgenera3onsperyear(i.e.vol3nism)maybe<1(semivol3ne)to7-8(mul3vol3ne)

÷  Onegenera3onperyear(univol3ne)mostcommoninCanada

÷  Overwinteringusuallyaslarvaeoradults;eggsandpupaesuscep3bletocold

÷  Overwinteringinfeedinggalleries,hiberna3ontunnelsorforestfloor(adultsonly)

e.g.mountainpinebeetle9

I.Broodproduc3on-5

÷  Withinaspecies,thenumberofgenera3onsperyearmayvarywithclima3ccondi3ons

÷  Climate-relatedpopula3onasynchronymaycausesignificantmortality

Adaptedfrom:Amman1973

Latitude (°North)

Ele

vatio

n (m

)

38 42 46 50 54 58 34

4000

3000

2000

1000

0

1-year cycle

Altitudinal limit

Mountainpinebeetlevol6nism

10

II.Emergence/dispersal-1

÷  Op3maltemperatureandhumidityrequiredforemergenceandflight

÷  Avoidrainandwinds>maximumflightspeed

÷  Shortwindowofemergencetomaximizechancesoffindingmates/hosts

Adaptedfrom:McCambridge1971

11

II.Emergence/dispersal-2

÷  Flightperiodmayberequiredbeforebeetlesbecomerecep3vetocuesfromhostsorconspecifics(otherbeetles)

÷  Dispersalbothshortandlongrange

÷  Mostbeetlesflybeneathcanopy(short-rangedispersal)

÷  Smallpercentageflyabovecanopy(long-rangedispersal)

÷  Upwindflightwhenseekinghostsormates

From:Safranyiketal.1992

Trap height (m)

Bee

tles

per t

rap

0 5 10 15 25 30

0.5

1.0

1.5

2.0

2.5

0 20

Above canopy

12

II.Emergence/dispersal-3

÷ Hostselec3on:randomlandingversusprimaryaYrac3on(acon3nuum)

÷ Cueso  Light/temperature(standdensity)o  Visual(largever3calsilhoueYes)o  Olfactory(e.g.ethanol,terpenes)

÷ Cascadeofdecisions:1.  Hostversusnon-hostspecies2.  Suscep3bleversusresistant3.  Highversuslowquality4.  Presence/absenceofcompe3tor

species5.  Presence/absenceofconspecifics

13

III.Coloniza3on-1

÷ Hostacceptancebasedongustatorys3mula3on(i.e.taste)

÷ Followingacceptance(bypioneerbeetles)o  Releaseofaggrega3on

pheromones(bothsexes)o  Responsebyconspecifics

(secondaryaYrac3on)

14

III.Coloniza3on-2

÷  TreesproduceresinasdefenseagainstaYack

÷  Mostbarkbeetlesselecttreeswithimpaireddefenseso  Drought,disease,windthrow,

suppression,ageo  “Secondaryspecies”

÷  Somespeciescanovercomedefensesofhealthytreeso  “Primaryspecies”

15

Primary(erup3ve)versussecondarybarkbeetles

Primary÷  Preferen3allyaYacklarge-diameter,

vigoroustrees(epidemicphase)÷  SuccessfulaYackrequirestree

mortality÷  Occasionallyundergopopula3on

erup3ons(i.e.outbreaks)andcausetreemortalityoverlandscapes

Secondary÷  Preferen3allyaYacksuppressedor

damagedtrees,windthroworloggingdebris

÷  Popula3onsdonoterupt

Barkbeetlescontendwiththewell-developeddefensesoftheirhostsbyeitheravoidingvigoroustrees(secondarybeetles)orovercomingthemthroughpheromone-mediatedmassaYacks(primarybeetles)

16

Primaryversussecondarybarkbeetles:BCexamples

Primary÷  Mountainpinebeetle

(Dendroctonusponderosae)Hosts=allpinespecies

÷  Sprucebeetle(Dendroctonusrufipennis)Hosts=allsprucespecies

÷  Douglas-firbeetle(Dendroctonuspseudotsugae)Host=Douglasfir

÷  Westernbalsambarkbeetle(Dryocoetesconfusus)Hosts=subalpinefir,amabilisfir

÷  Westernpinebeetle(Dendroctonusbrevicomis)Host=ponderosapine

Secondary(afewofmany)÷  Pineengraver

(Ipspini)Hosts=lodgepole,ponderosa,whitepine

÷  Firengraver*(Scolytusventralis)Hosts=truefirs

÷  Silverfirbeetle(Pseudohylesinusgrandis)Hosts=amabilis,grandfir,Douglasfir,westernhemlock

÷  IpsperturbatusHosts=sprucespecies

*some3mesconsideredprimary

17

III.Coloniza3on-3

÷  Successfulcoloniza3oncon3ngentontreedeatho  Therefore,highlyevolved

defensiveresponses÷  Cons3tu3veresinosus

o  Preformedresinductsorpocketsexudepitch

o  Mainlyphysicalbarrier÷  Inducedresinosus

o  Cellularnecrosisandreleaseoftoxins

÷  Defense≡vigour

Treedefenses

18

III.Coloniza3on-4

÷  Symbiosis:twounlikeorganismslivingtogetherformutualbenefit

÷  Allbarkbeetlescarrysymbio3corganisms–mostlyfungi

÷  Themutualbenefits:o  Fungus = transporttonewhostso  Beetle = treepathogen

= habitatmodifica3on= nutri3on

÷  Mycangia(adj.=mycangial)o  Structuresthatcarryandsome3mesnurture

fungalsporeso  Locatedmainlyonheadormouthparts

÷  Phoresy(adj.=phore3c)o  Sporescarriedonbody

Symbionts

19

III.Coloniza3on-5

÷  Barkbeetles(andotherinsects)producechemicalcompoundstocommunicate(=semiochemicals*)

÷  Hostchemicalsmodifiedtoproducepheromones

÷  Aggrega3onpheromonesfacilitatemassaYacks

÷  Treedefenses“swamped”

Aggrega3on

20

*Semiochemicals1

÷  Chemicalmessengers÷  Pheromones:

causeaspecificreac3oninareceivingorganismofthesamespecies

÷  Kairomones:evokeinthereceiverareac3onthatfavoursthereceiverbutnottheemiYer

÷  Allomones:evokeinthereceiverareac3onthatfavourstheemiYerbutnotthereceiver

Tree monoterpenes

21

SEMIOCHEMICAL

Territorialkairomone• usedinfindingorrejec3ngpoten3alhostbyrespondingbarkbeetlespecies

Kairomone• usedbypredatorsandparasitestolocatetheirbarkbeetlehost

Behaviour-modifyingpheromone• inducingstridula3on,reproduc3veac3vity,etc.

An3-aggrega3onpheromone• regula3ngaYackdensity

Territorialallomone• usedforiden3fyingoccupiedhabitatforsoleuseoffirstaYackingbarkbeetlespecies

Aggrega3onpheromone• promo3ngpopula3onconcentra3on

Possiblemul3plefunc3onofoneormoresemiochemicals

*Semiochemicals2

22

III.Coloniza3on-6a

÷  Intraspecificcompe33onsignificantdensity-dependentmortality

÷ Op3malaYackdensitytoovercometreeresistancebeforecompe33veeffects

÷ Mechanismstominimizeovercrowding:o  Stridula3ono  An3-aggrega3onpheromones

0

Bro

od/a

ttack

Attack density (galleries/m2) 0 20 40 60 80 100 120

2

4

6

8

10

12

From:RaffaandBerryman1983

Compe33on

23

III.Coloniza3on-6b

÷ Treequality=phloemthickness:o  BeYernutri3ono  Lesscompe33ono  Fasterdevelopmento  Moreoffspring

Num

ber o

f bee

tles/

m²

Phloem Thickness (cm)

Males

0.15 0.25 0.35 0.45 0

10

20

30

40

50

From:AmmanandCole1983

Resourcequality

24

III.Coloniza3on-6c

÷ Phloemthicknessaffectedby:o  Treeageo  Treesizeo  Treevigouro  Standdensity

No.

atta

ckin

g be

etle

s

0

500

1000

1500

2000

2500

r2 = 0.67 P < 0.001

r2 = 0.71 P < 0.001

r2 = 0.16 P = 0.015

Crown volume (m3)

0 1000 2000 3000 4000

Tree age (yrs)

20 40 60 80 100 120

Diameter (cm) at breast height (1.3m)

10 20 30 40 50

From:SafranyikandCarroll2006

Resourcequality

25

III.Coloniza3on-7a

Invertebrates Vertebrates Pathogens

÷  Predators,parasitoids,diseases÷  Regulatemostbarkbeetlepopula3ons÷  Erup3vespecies“escape”regula3on

Naturalenemies

26

III.Coloniza3on-7b

÷  Woodpeckersthemostimportantnaturalenemiestosmallmountainpinebeetlepopula3ons

0

20

40

60

80

100

1965

1966

1967

1968

% o

f tot

al m

orta

lity

Year

Other

Woodpecker spp.

Invertebrates

0

20

40

60

80

100

1965

1966

1967

1968

% o

f tot

al m

orta

lity

Year

Other

Woodpecker spp.

Invertebrates

Other

Woodpecker spp.

Invertebrates

From:SafranyikandCarroll2006

Naturalenemies

27

III.Coloniza3on-8

÷  Largestsourceofmortalityfollowingcoloniza3on

÷  Primarilytemperaturerelatedo  Directeffectsonbeetles

•  Growthanddevelopmentthresholds

•  Developmentrates•  Acquiredcoldhardiness•  Survival

o  Indirecteffectsonhosttrees•  Phloemmoisture

÷  Beetleadapta3ons:o  Diapauseo  Coldtolerance

Tem

pera

ture

(ºC

)

Oct. Nov. Dec. Jan. Feb. Mar. Apr. May Jun.

Initial mortality

50% mortality

100% mortality-40

-35

-30

-25

-20

-15

-10

Tem

pera

ture

(ºC

)

Oct. Nov. Dec. Jan. Feb. Mar. Apr. May Jun.

Initial mortality

50% mortality

100% mortality-40

-35

-30

-25

-20

-15

-10

From:Wygant1940

Abio3cmortalityfactors

28

Summary(e.g.univol3nebarkbeetle)

CLIMATECLIMATE TREE

RESISTAN

CE

DEADTREE

LIVING DYING DEAD

BARKBEETLESEMERGE

SUMMER FALL NEXT SUMMER

NATURAL ENEMIESCOMPETITIONCOMPETITION

FUN

GU

S

BARKBEETLE FUNGUS

CLIMATECLIMATE

CLIMATECLIMATE

CLIMATECLIMATE TREE

RESISTAN

CE

DEADTREE

LIVING DYING DEAD

BARKBEETLESEMERGE

SUMMER FALL NEXT SUMMER

NATURAL ENEMIESCOMPETITIONCOMPETITION

FUN

GU

S

BARKBEETLE FUNGUS

CLIMATECLIMATE

CLIMATECLIMATE

Colonization Emergence/dispersal Brood production

29