Chapter 53:

Community Ecology

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When Connell removed Balanus from the lower strata, the Chthamalus population spread into that area.

The spread of Chtamalus when Balanus was removed indicates that competitive exclusion makes the realizedniche of Chthamalus much smaller than its fundamental niche.

RESULTS

CONCLUSION

Ocean

Ecologist Joseph Connell studied two baranacle speciesBalanus balanoides and Chthamalus stellatusthat have a stratified distribution on rocks along the coast of Scotland.

EXPERIMENT

In nature, Balanus fails to survive high on the rocks because it isunable to resist desiccation (drying out) during low tides. Its realized niche is therefore similar to its fundamental niche. In contrast, Chthamalus is usually concentrated on the upper strata of rocks. To determine the fundamental of niche of Chthamalus, Connell removed Balanus form the lower strata.

Low tide

High tide

Chthamalusfundamental niche

Chthamalusrealized niche

Low tide

High tideChthamalus

Balanusrealized niche

Balanus

Ocean

Figure 53.2 Can a species’ niche be influenced by interspecific competition?

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Figure 53.4 Character displacement: indirect evidence of past competition

G. fortis

Beak depth (mm)

G. fuliginosa

Beak depth

Los Hermanos

Daphne

Santa María, San CristóbalSympatric populations

G. fuliginosa, allopatric

G. fortis, allopatric

Per

cen

tag

es o

f in

divi

dua

ls in

eac

h si

ze

clas

s

40200

40200

40200

8 10 12 14 16

Figure 53.5 Cryptic coloration: canyon tree frog

Figure 53.6 Aposematic coloration: poison arrow frog

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Figure 53.7 Batesian mimicry: A harmless species mimics a harmful one

(a) Hawkmoth larva

(b) Green parrot snake

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Figure 53.8 Müllerian mimicry: Two unpalatable species mimic each other

(a) Cuckoo bee

(b) Yellow jacket

Figure 53.9 Mutualism between acacia trees and ants

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

Figure 53.10 A possible example of commensalism between cattle egrets and water buffalo

Figure 53.12 Examples of terrestrial and marine food chains

Quaternary consumers

Tertiary consumers

Secondary consumers

Primary consumers

Primary producers

Carnivore

Carnivore

Carnivore

Herbivore

Plant

Carnivore

Carnivore

Carnivore

Zooplankton

PhytoplanktonA terrestrial food chain A marine food chain

Figure 53.13 An antarctic marine food web

Humans

Baleen whales

Crab-eater seals

Birds Fishes Squids

Leopardseals

Elephant seals

Smaller toothed whales

Sperm whales

Carnivorous plankton

Euphausids (krill)

Copepods

Phyto-plankton

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Figure 53.18 Beavers as ecosystem “engineers” in temperate and boreal forests

Figure 53.27 The equilibrium model of island biogeography

Number of species on island

(a) Immigration and extinction rates. The equilibrium number of species on anisland represents a balance between the immigration of new species and theextinction of species already there.

(b) Effect of island size. Large islands may ultimately have a larger equilibrium num-ber of species than small islands because immigration rates tend to be higher and extinction rates lower on large islands.

Number of species on island Number of species on island

(c) Effect of distance from mainland. Near islands tend to have largerequilibrium numbers of species thanfar islands because immigration ratesto near islands are higher and extinctionrates lower.

Equilibrium number

Rat

e of

imm

igra

tion

or e

xtin

ctio

n

Rat

e of

imm

igra

tion

or e

xtin

ctio

n

Rat

e of

imm

igra

tion

or e

xtin

ctio

n

Small island Large island Far island Near island

Imm

igration

Extin

ctio

n

Extin

ctio

n

Imm

igration

Extin

ctio

n

Imm

igration

(small island)

(larg

e is

land)

(large island)

(sm

all

isla

nd) Im

migration Ex

tinct

ion

Imm

igration

(far island)

(near i

sland)

(near island) (far i

slan

d)

Extinctio

n

Table 53.1 Interspecific Interactions