chapter 16 species abundance and diversity. 1st question of the day define the term “community”
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Chapter 16 Species Abundance and Diversity
1st Question of the Day
Define the term “Community”
1st Question of the Day
Define the term “Community”
An association of interacting species inhabiting some defined area.
Chapter 16 Species Diversity
Objectives:1. Identify the abundance distributions of species in
a community
2. Determine objective measures of species diversity
3. Determine how many species there exist in the world
4. Identify trends in species diversity distribution
5. Relate the concepts of diversity and stability
Log-Normal Pattern of Species Abundance In Communities
Very few species have extremely high relative abundance
Why ?
Low ◄ Abundance ► High(Log Scale)
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Log-Normal Pattern of Species Abundance In Communities
Very few species have extremely high relative abundance
Very few species have extremely low relative abundance
Most species are moderately abundant
Plants
Birds
Low ◄ Abundance ► High(Log Scale)
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Species Abundance
Log normal distributions are thought to be a consequence of species in a community subdivided niche space.
What does this mean?
Species Richness
How many species exist in the world?
• E. O. Wilson found 1.4 million classified
• Most ecologist agree 3-10 million
• E. O. Wilson estimates 100 million
Problem!!!!
Hard to measure (or find) the dang critters!!!
Species Richness
Terry Erwin:
Tropical rain
forest insects
Species Richness
30 - 40m
Species Richness
Bug Bomb to
the tree tops----
Species Richness
Bug Bomb to
the tree tops----
Funnels to catch
Insects as they
fell---
Terry Erwin
Species Diversity
Erwin’s results
• 163 species of beetles in one species of tree Luehea seemannii
• Estimated 50,000 tropical tree species
• If this typical - then 8,150,000 canopy dwelling tropical beetles
• Beetles represent 40% of arthropods
Species Diversity
• In tropical canopy - 20 million species arthropods
• Twice as many arthropods in canopy as on the ground - 30 million tropical species
Conclusions:
From 163 beetles - expanded to 30 million arthropod species in tropical rain forests
Species Diversity
Stork - Similar techniques to Erwin
Indonesia
• 10-80 million species on earth
Species Richness
How many species exist in the world?
• E. O. Wilson found 1.4 million classified
• Most ecologist agree 3-10 million
• E. O. Wilson estimates 100 million
Species Diversity
Bacteria:
Pinch of soil -
• Quarts grains
• decaying organic matter
• free nutrients
• 10 billion bacteria
Species Diversity
Pinch of soil -• 1/1,000,000 of the pinch• Spread out on agar plate and grow - expect
10,000 bacterial colonies• How many do we see? 10-100 colonies
Species Diversity
Bacteria:
Bergey’s Manual of Systematic Bacteriology
4,000 species of bacteria
How many exist? Unknown, and limited by technology to grow them.
Species Diversity
Definition:
1. A measure of the number of species (species richness) and
2. The relative abundance (evenness) within a community.
Species Diversity
Low Diversity:
either few species or highly uneven abundances
High Diversity:
large number of species or very even abundances
Fig. 16.5
Species Diversity
AAAA ABCD ABCD
AAAA AAAA DCBA
AAAA AAAA BCAD
AAAA AAAA CDAB
Species Diversity
AAAA ABCD ABCD
AAAA AAAA DCBA
AAAA AAAA BCAD
AAAA AAAA CDAB
Lowest Highest
Diversity DiversityShannon-Weiner Index
Pages 374-375Table 16.1
Species Diversity
Some Assumptions -Species Diversity Indices
1. All species have equal impact on the community
2. No account made for variation within a species (e.g., larvae or adult)
Species Diversity
Some Assumptions -Species Diversity Indices
3. Species accounts can be taxonomically difficult
4. Cannot compare different communities (e.g., plankton and fish, tree and insect)
Species Diversity
OK-- We can’t measure all the species in the world (at least not at the moment)
But!!!
Can we get some guidance or hints where biodiversity is greatest???
Species Diversity
More land area to develop and no barriers to spread of species
Biodiversity Hotspots
Latitudinal Trends at Different Latitudes
8 40 72Latitude
Number of
species
75
50
25
QuadrupedalMammals
(4 legged furry things!)
Muncie
Species Diversity
Why?
Three reasons----------
Species Diversity
1. With environmental (habitat) heterogeneity, species diversity increases, compared to uniform environments - greater niche differentiation and resource partitioning
Species Diversity
Environmental heterogeneity: can be defined as "with parts that are different".
Resource partitioning: avoidance of, or reduction in, competition for similar resources by individuals of different species occupying different nonoverlapping ecological niches
Foliage Height and Bird Species Diversity
MacArthor’s warblers
Fig. 16.9
Species Diversity
Variant nutrient (and moisture) availability
Variation in Nitrate and Soil Moisture
Different plant species are the superior competitor under different soil conditions. Complex environment prevents competitive exclusion.
Variation in Soil Conditions Is Associated With Variation In Species Composition of Plant
Communities.
Fig. 16.14
Species Diversity
2. Nutrient Availability: High species diversity occurs in environments with LOW nutrient availability.
In high nutrient environments, competition for LIGHT dominates. Competitive exclusion is more likely to drive some species extinct.
Soil Fertility and Plant Species Diversity(Rain Forest in Ghana, Africa)
Species Diversity
3. Disturbance:
Question for the Day!
What level of disturbance (e.g., fire, drought, local condo development, etc.) would be associated with the highest and lowest diversity levels? Pick from low, medium, and high disturbance levels. Of course, defend your answer---------
Fig. 16.18
Species Diversity - Who Cares?
Principle of Community Ecology:
Diversity and stability are causally related.
More StableLess Stable
Species Diversity
Why?
1. Increasing species diversity leads to more complex interactions: e.g., more species, more predation, more competition, more parasitism
2. Complex systems are more stable: changes in a single species have less impact
Stability
Two parts:
1. Resistance - the ability of a system to resists perturbation
2. Resilience - the ability of a system to return to normal following disturbance
Species Diversity
What if----
An exotic species enters a community. (Presumably) it would immediately increase species richness, but would it increase species diversity overall???????????????
Kudzu
Zebra Mussels
EuropeanStarling
Nile Perch
Summary for Today!
1. Determined abundance distributions and species richness
2. Determined species diversity is a mix of abundance and eveness
3. Identified reasons for levels of species diversity
4. Diversity and stability are related concepts
Species Diversity
• Intermediate Levels of Disturbance -
# of Species
Frequency or intensity of disturbance
Low High