LB 144: Organismal Biology
Class 2404.14.16
Community Ecology I
Announcements
Readings:Chapter 55, Section 55.1 (pages 1123-1145)
Homework 7 Due Today
You should be able to:1. Describe, compare & contrast, and provide examples of
different types of interspecific interactions and their effects on fitness and short-term ranges and abundances.
2. Explain and give examples of links between current interspecific interactions and evolution (Ex: character displacement, arms races, and fitness effects on interacting species).
Objectives
4
TermsCommunityCommensalismCompetition Consumption Mutualism IntraspecificInterspecificCompetitive exclusion principle NicheFundamental nicheRealized niche
Niche differentiation Character displacementHerbivory Parasitism Predation CarnivoreMimicry Batesian mimicryMullerian mimicry Evolutionary arms race
5
Community EcologyBiological community- all the species that interact in a certain area.
6
Community EcologyAbiotic factors- Non-living factors in the environment that influence an organism’s distribution and abundance
Biotic factors- living factors that (e.g., competition) that influence the distribution and abundance of organisms.
Species interactions
7
Species interactions
Interspecific interactions:
4 Main Types:1. Commensalism2. Competition 3. Consumption 4. Mutualism
Effects on Fitness?+ Positive - Negative 0 None
1) Commensalism
1) Commensalism
1) Commensalism
1) Commensalism Human Commensals Rats (Rattus spp.)House Mice (Mus musculus)Raccoons (Procyon lotor)House Sparrows (Passer domesticusa)Turf Grass (Cynodon dactylon)
Cattle egret (Bubulcus ibis)
2) Competition: INTRA- and INTERspecific
– MANY Types:
• Consumptive
• Preemptive
• Overgrowth
• Chemical
• Encounter
• Territorial
2) Competition:
Interspecific competition:
Ecological niche:
The Consequences of Competition
2) Competition:
2) Competition:
Competitive exclusion occurs when competition is asymmetric.
Re
lati
ve F
itn
ess
Species A Alone
Species B Alone
Species A+B Together
Asymmetric Competition
2) Competition:
Competitive exclusion occurs when competition is asymmetric.
Re
lati
ve F
itn
ess
Species A Alone
Species B Alone
Species A+B Together
Symmetric Competition
2) Competition:
2) Competition:
2) Competition:
2) Competition:
2) Competition:
Competitive Exclusion Principle: A test
Balanus: Upper limit of distribution limited by water levelChthamalus: Lower limit of distribution limited by competition
Figure 19.7
1) A. ricordii
2) A. distichus
3) A. aliniger
4) A. cybotes
7) A. insolitus
6) A. christophei
5) A. etheridgei
A. Distichus – sunny fenceposts
A. Insolitus – shady branches
Resource Partitioning – An example
Fig. 54-4
Los Hermanos
G. fuliginosa G. fortis
Beakdepth
Daphne
G. fuliginosa,allopatric
G. fortis,allopatric
Sympatricpopulations
Santa María, San Cristóbal
Beak depth (mm)
Per
cen
tag
es o
f in
div
idu
als
in
ea
ch s
ize
cla
ss
60
40
20
0
60
40
20
0
60
40
20
08 10 12 14 16
Character displacement
3) Consumption = predation, parasitism, herbivory
Plant defenses against herbivores:
– Chemical toxins
– Spines and thorns
Animal defenses against predators:
– Passive defenses
– Active defenses
Adaptations of the consumed:
3) Consumption
Summary Table 55.1
• Passive camouflage/ cryptic coloration defenses
• Passive mechanical/ chemical defenses (e.g. warning coloration)
Figure 19.10
Figure 19.11
Toxins from: • Synthesis• Acquisition
Passive mimicry defenses = “copycat” adaptation
Batesian mimicry = A palatable/ harmless species mimics an unpalatable/ harmful species
Figure 19.12
Figure 19.13
Müllerian mimicry = >2 unpalatable species resemble each other
3) Consumption
Inducible defenses:– Alarm calls
– Mobbing
– Distraction displays
Figure 19.8
Figure 19.9
3) Consumption
Figure 55.10
Are mussel defenses induced
by the presence of crabs?
Mussels increase investment in defense in the
presence of crabs.
Mussels do not increase investment in
defense in the presence of crabs.
Seawater
Crab
(fed fish, not mussels)No crab
Mussels Mussels
Mussels downstream of the crab tank will have
thicker shells than mussels downstream of the empty tank.
Mussels in the two
tanks will have shells of equal thickness.
Average shell
thickness is
significantly higher
downstream of
the crab
No crab CrabSh
ell th
ic
ke
nss (m
m)
Mussels increase investment in defense when
they detect crabs. Shell thickness is an inducible defense.
Reminder: Practice your scientific
explanations with each data figure: Claim,
evidence, and reasoning
Figure 19.15
Adaptation and arms races
4) Mutualism
Many mutualistic relationships have evolved from predator-prey or host-parasite interactions
Figure 19.16