Download Community Structure Symbiosis Succession

Reading
Goals
Community Structure
Symbiosis
Succession
Chapter 15
Read for vocabulary
375-377
Confidence Interval Box on 387
Summary 393-394
Chapter 17
Read for vocabulary
419-425
427-429
Box 430
432-434
Summary 438
Chapter 21
Chapter 16
Read for vocabulary
398-411
Summary 415-416
Read for vocabulary
512-518
519-522
525-529
530-533
Summary 533
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Community Structure
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Community Structure
Characteristics of Communities
Vertical Structure
Physical Structure
•Vertical layers
•Horizontal (patchiness)
•dispersion
Biological Structure
•Guilds
•Dominants
•Complexity
•diversity
Horizontal Structure
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Community Structure
Community Structure
Canopy
Mid- Canopy
Understory
Organic Layer
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Community Structure
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Community Structure
Diversity and Stability
How would structure look in a Kelp Forest? Desert ?
Does diversity of a system affect its stability?
How would structure look PNW Stream ?
What do we mean by diversity? Stability
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Community Structure
Diversity and Stability
Community Structure
Two groups of Theories concerning Stability and Diversity in Communities
Does diversity of a system affect its stability?
Equilibrium
Persistence – ability to survive disturbance
Non- Equilibrium
Resilience – ability to rebound following a disturbance
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Community Structure
Equilibrium
Community Structure
Non-Equilibrium
Diversity is determined by the number of available niches
•
•
Traditional view
Number of species does not fluctuate markedly from an
equilibrium determined by
•Predation
•Competition
• Disturbances are dampened out
• New species can invade only after similar species leave
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•
•
Species diversity is dynamic
Community structure determined by disturbance
• prevents dominance
• increases horizontal structure
• can increase or decrease diversity
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Community Structure
Response to Disturbance
Community Structure
Response to Disturbance
Non-Equilibrium models
‘K’
Equilibrium models
Pop Size
Pop Size
‘r’
‘r’
Co-existence
‘K’
Time after disturbance
•Fast growth
•Early maturation
•High fecundity
•Small size
•Good colonizers
Time after disturbance
•slow growth
•late maturation
•low fecundity
•large size
•Good competitors
Diversity maintained by frequent disturbance
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Community Structure
Community Structure
Intermediate Disturbance Hypothesis
Pop Size
Examples
low
biodiversity is highest when
disturbance is neither too rare nor
too frequent.
•Coral reefs and hurricanes
•Tropical forests and tree gaps
•Boulders in intertidal areas
•Prairie dogs in grasslands
high
Frequency of disturbance
or size of disturbance
or frequency of population reduction
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Community Structure
Community Structure
A keystone predator is an
animal that is important for
maintaining species richness
(number of species) in a
community. Keystone
predators feed on different
species that normally would
compete with each other.
Competitive exclusion of a
species does not occur
because the densities of
competitors are kept
reduced by a common
predator.
Dynamic Equilibrium Model
•
community structure is maintained by
controlling competitive interactions
between species (e.g., keystone
species)
Page 423 in Text
A good example of a keystone predator is Piaster, a sea star,
that reduces the populations of a mussel, Mytilus. If Piaster is
experimentally removed from the community, the species
richness of the community decreased from 15 to 8 species.
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Community Structure
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Community Structure
Some Terms
Species Richness (S) – number of species in an area (number of ind. /
area)
Diversity Values – used to
•Establish trends
•Make comparisons
•Produce conservation policies
Species Diversity – number of species in a community or region
OR
Differences between biomes
• Tropical rainforest – 50-100 spp. per ha
• grasslands, savannas, deciduous forests 15-60 spp. per ha
• Tiaga, redwood forests, dry deserts, open ocean 7-20 spp. per ha
Is there more . . . .
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Community Structure
Community Structure
Problems with Species Richness Values –
•
•
No. spp. will increase with sample size
May not provide useful information about ecology of a
community (e.g., abundance or physical structure may have
more significance than richness).
Therefore, ecologists tend to use Diversity Indices rather than just
Species Richness (S) when talking about Diversity
Many diversity Indices
Incorporate both richness (S) and evenness (relative abundance)
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Community Structure
In the graph below, species richness and the Shannon diversity index
(symbol H, see below for its calculation) are provided for each community.
You can see that the diversity index H is lower for the communities at the
left, indicating their lower diversity.
Community Structure
Also, other types of Diversity besides Species Diversity ….
Scale
S= Species Richness
Gamma Diversity
Alpha Diversity
(regional)
(local)
Beta Diversity
(species turnover)
http://images.google.com/imgres?imgurl=http://www.worldagroforestry.org/sites/rsu/resources/biodiversity/anal
ysistypes/Divers2.gif&imgrefurl=http://www.worldagroforestry.org/sites/rsu/resources/biodiversity/analysistypes
/diversityindices.asp&h=275&w=478&sz=6&tbnid=HbjImINhNF0J:&tbnh=72&tbnw=126&hl=en&start=17&prev
=/images%3Fq%3Ddiversity%2Bevenness%26svnum%3D10%26hl%3Den%26lr%3D%26sa%3DG
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Increasing scale
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Community Structure
Community Structure
Conserving ‘ Diversity’
• Tend to focus on species – even only rare species
Alpha – diversity of small areas of relatively homogenous habitat; No.
spp. per unit area. Used to describe community structure.
Beta – change in species composition over relatively small distances;
often used between distinct adjacent habitats. Used to describe
species turnover.
Gamma – diversity of similar habitat separated by wide geographic
distances; regional diversity. Used to address the relative roles that
history and ecology have played in organizing assemblages of
species.
• Current efforts starting to shift to conserving complete
ecosystems
• There are an estimated 10-30 million species
described in the world; only 1.7 million described!
• Extinction rates are increasing
• natural rate 2-25 spp. / yr
• present rate 10,000 spp. / yr.
Causes of Extinction? Why worry about conserving ?
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Symbiosis
Symbiosis – intimate association between individuals of two
different species living together
Symbiosis
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Species 1
Species 2
Parasitism
+
-
Commensalism
+
No effect
Mutualism
+
+
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Symbiosis
Symbiosis
Types of Mutualism
Mutualism
Defensive – food or
shelter in return for
defense
Trophic exchange of
nutrients and
energy
Facultative – partners can live singly
Obligate – partners cannot exist singly
Dispersive – food in
return for moving
propagules or pollen
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Symbiosis
Symbiosis
Lichen –
fungus and
cyanobacteria or green
algae
Soybean & Rhizobium
Species 1
Species 2
Parasitism
+
-
Parasitism
+
-
Commensalism
+
No effect
Commensalism
+
No effect
Mutualism
+
+
Mutualism
+
+
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Species 1
Species 2
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Symbiosis
Symbiosis
Cocklebur & Animals
Lichen on a Tree
Species 1
Species 2
Species 1
Species 2
Parasitism
+
-
Parasitism
+
-
Commensalism
+
No effect
Commensalism
+
No effect
Mutualism
+
+
Mutualism
+
+
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Symbiosis
Symbiosis
Remora and Shark
Ants and Acacia
Species 1
Species 2
Parasitism
+
-
Parasitism
+
-
Commensalism
+
No effect
Commensalism
+
No effect
Mutualism
+
+
Mutualism
+
+
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Species 1
Species 2
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Symbiosis
Sawfly (Pontania sp.) larva inside
a gall. Note the external
parasitoid larva (translucent
white) attached to the dorsal
surface of the sawfly larva.
http://images.google.com/imgres?imgurl=http://tiee.ecoe
d.net/vol/v3/experiments/sawfly/img/sawfly(parasite)%25
5BHR%255D.jpg&imgrefurl=http://tiee.ecoed.net/vol/v3/
experiments/sawfly/downloads.html&h=1061&w=721&sz
=107&tbnid=IwoeejTl0bMJ:&tbnh=150&tbnw=101&hl=e
n&start=9&prev=/images%3Fq%3Dparasite%26svnum
%3D10%26hl%3Den%26lr%3D
Species 1
Species 2
Parasitism
+
-
Commensalism
+
No effect
Mutualism
+
+
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