Chapter 53Chapter 53

Community EcologyCommunity Ecology

I. Interspecific InteractionsI. Interspecific Interactions

CompetitionCompetition– Competitive exclusion principleCompetitive exclusion principle– Niche – fundamental vs. realizedNiche – fundamental vs. realized– Resource partitioningResource partitioning– Character displacementCharacter displacement

PredationPredation– AdaptationsAdaptations

Cryptic colorationCryptic coloration

Aposemetic colorationAposemetic coloration

MimicryMimicry

Table 53-1

LE 53-2

Chthamalusfundamental niche

High tide

Low tideOcean

Chthamalusrealized niche

High tide

Low tideOcean

Balanusrealized niche

Chthamalus

Balanus

LE 53-3A. insolitususually percheson shady branches.

A. ricordii

A. insolitus

A. christophei

A. cybotes

A. etheridgei

A. alinigerA. distichus

A. distichusperches onfence postsand othersunnysurfaces.

LE 53-4

Beakdepth

Sympatricpopulations

G. fuliginosaG. fortis

Santa María, San Cristóbal

40

20

0

Los Hermanos

40

20

0

Daphne

40

20

0

G. fuliginosa,allopatric

G. fortis,allopatric

Beak depth (mm)

161412108

Pe

rce

nta

ge

of

ind

ivid

ua

ls i

n e

ac

h s

ize

cla

ss

Figure 53-05

Figure 53-06

LE 53-7

Hawkmoth larva

Green parrot snake

LE 53-8

Cuckoo bee

Yellow jacket

HerbivoryHerbivory

ParasitismParasitism– Endoparasites, ectoparasites and Endoparasites, ectoparasites and

parasitoidismparasitoidism

Disease - pathogensDisease - pathogens

MutualismMutualism

CommensalismCommensalism

II. Dominant and Keystone Species II. Dominant and Keystone Species and Control of Communityand Control of Community

Species diversitySpecies diversity– Species richnessSpecies richness– Relative abundanceRelative abundance

Trophic structureTrophic structure– Food webs (Fig. 53.13)Food webs (Fig. 53.13)– Limits on lengthLimits on length

Energetic hypothesisEnergetic hypothesis

Dynamic stability hypothesisDynamic stability hypothesis

LE 53-11

Community 1

AB

C

D

A: 25% B: 25% C: 25% D: 25%

Community 2A: 80% B: 5% C: 5% D: 10%

LE 53-12

Quaternaryconsumers

Tertiaryconsumers

Carnivore

Carnivore

Carnivore

Carnivore

Secondaryconsumers

CarnivoreCarnivore

Primaryconsumers

ZooplanktonHerbivore

Primaryproducers

PhytoplanktonPlant

A terrestrial food chain A marine food chain

LE 53-13

Euphausids(krill)

Carnivorousplankton

Phyto-plankton

Copepods

Squids

Elephantseals

FishesBirds

Crab-eaterseals

Leopardseals

Spermwhales

Smallertoothedwhales

Baleenwhales

Humans

LE 53-14

Zooplankton

Fish larvae

Fish eggs

Sea nettle Juvenile striped bass

LE 53-15

Productivity

Nu

mb

er o

f tr

op

hic

lin

ks

Nu

mb

er o

f sp

ecie

s

No. of trophiclinks

No. of species

High(control)

6

5

4

3

2

1

0

6

5

4

3

2

1

0Medium Low

Species with a Large ImpactSpecies with a Large Impact– Dominant speciesDominant species– Keystone species (Fig. 53.16, p. 1168)Keystone species (Fig. 53.16, p. 1168)– Foundation speciesFoundation species

Bottom-Up and Top-Down ControlsBottom-Up and Top-Down Controls– Bottom-Up: NBottom-Up: NVVHHPP

Nutrients are limiting factorsNutrients are limiting factors

– Top-Down: NTop-Down: NVVHHPPPredation is limiting factorPredation is limiting factor

LE 53-16

Without Pisaster (experimental)

With Pisaster (control)

1963 ’64 ’65 ’66 ’67 ’68 ’69 ’70 ’71 ’72 ’73

20

15

10

5

0

Nu

mb

er

of

sp

ec

ies

pre

se

nt

LE 53-17

100

80

60

40

0

20

Sea otter abundance

Ott

er

nu

mb

er

(% m

ax

. c

ou

nt)

400

300

200

0

100

Sea urchin biomass

Gra

ms

pe

r0

.25

m2

10864

02

Total kelp density

Nu

mb

er

pe

r0

.25

m2

19971993198919851972Year

Food chain beforekiller whaleinvolvement inchain

Food chain afterkiller whales startedpreying on otters

Figure 53-18

LE 53-19

Nu

mb

er o

f p

lan

t sp

ecie

s

8

6

4

0

2

Conditions

WithJuncus

WithoutJuncusSalt marsh with Juncus

(foreground)

LE 53-20

Per

cen

tag

e o

fh

erb

aceo

us

pla

nt

cove

r100

75

50

0

25

Rainfall (mm)

200 300 4000 100

LE 53-UN1171

Polluted State Restored State

Fish Abundant Rare

Zooplankton AbundantRare

Algae Abundant Rare

III. Disturbance Influences III. Disturbance Influences CommunitiesCommunities

Definition and causesDefinition and causes– Changes in community and removal of Changes in community and removal of

speciesspecies– Human rolesHuman roles

Ecological successionEcological succession– PrimaryPrimary– SecondarySecondary

LE 53-21

Before a controlled burn.A prairie that has not burned for several years has a high propor-tion of detritus (dead grass).

During the burn. The detritus serves as fuel for fires.

After the burn. Approximately one month after the controlled burn, virtually all of the biomass in this prairie is living.

LE 53-22

Soon after fire. As this photo taken soon after the fire shows, the burn left a patchy landscape. Note the unburned trees in the distance.

One year after fire. This photo of the same general area taken the following year indicates how rapidly the com-munity began to recover. A variety of herbaceous plants, different from those in the former forest, cover the ground.

LE 53-24Pioneer stage, with fireweed dominant

Dryas stage

Spruce stageNitrogen fixation by Dryas and alder

increases the soil nitrogen content.

Successional stage

DryasPioneer Alder Spruce

So

il n

itro

gen

(g

/m2)

60

50

40

30

20

10

0

IV. Biogeographic Factors on IV. Biogeographic Factors on CommunityCommunity

Equatorial-Polar gradientsEquatorial-Polar gradients

Area effectsArea effects– Species-area curve (p. 1176)Species-area curve (p. 1176)

Island equilibrium modelIsland equilibrium model– Size and distance from mainlandSize and distance from mainland– Immigration/extinctionImmigration/extinction

LE 53-25

Trees

Tre

e sp

ecie

s ri

chn

ess

180

160

140

120

100

80

0

Ver

teb

rate

sp

ecie

s ri

chn

ess

(lo

g s

cale

)

200

100

50

10

60

40

20

1,100900700500300100Actual evapotranspiration (mm/yr)

Vertebrates

2,000Potential evapotranspiration (mm/yr)

1,5001,000500

LE 53-26

Nu

mb

er o

f sp

ecie

s (l

og

sca

le)

1,000

Area (acres)

1010109106 107 108103 104 1051 10 100

100

10

1

LE 53-27

Immigration and extinction rates

Number of species on island

Equilibriumnumber

Imm

igration

Rat

e o

f im

mig

rati

on

or

exti

nct

ion

Extin

ctio

n

Effect of island size

Number of species on island

Smallisland

Imm

igration

Rat

e o

f im

mig

rati

on

or

exti

nct

ion

Extin

ctio

n

Largeisland

(large island)

Imm

igration

(small island)

Extin

ctio

n

(larg

e is

land)

(sm

all i

slan

d)

Effect of distance from mainland

Number of species on island

Farisland

Imm

igration

Rat

e o

f im

mig

rati

on

or

exti

nct

ion

Extin

ctio

n

Nearisland

(near island)

Imm

igration

(far island) Extinctio

n

(near i

sland)

(far i

slan

d)

LE 53-28

Area of island (mi2)(log scale)

400N

um

ber

of

pla

nt

spec

ies

(lo

g s

cale

)

1,0001001010.1

200

100

50

25

10

5

V. Views of Community StructureV. Views of Community Structure

Integrated hypothesisIntegrated hypothesis

Individualistic hypothesisIndividualistic hypothesis

LE 53-29

Trees in the Santa Catalina Mountains

Nu

mb

er

of

pla

nts

pe

r h

ec

tare

Moisture gradientWet

600

400

200

0

Environmental gradient(such as temperature or moisture)

Po

pu

lati

on

de

ns

itie

s o

fin

div

idu

al

sp

ec

ies

Individualistic hypothesis

Environmental gradient(such as temperature or moisture)

Po

pu

lati

on

de

ns

itie

s o

fin

div

idu

al

sp

ec

ies

Integrated hypothesis

Dry