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Chapter 53:
Community Ecology
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
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?
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
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
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Figure 53.7 Batesian mimicry: A harmless species mimics a harmful one
(a) Hawkmoth larva
(b) Green parrot snake
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
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
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
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