Transcript Chapter 12 Species Diversity

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
Very few species have extremely
high relative abundance
Why ?
Number of Species
Log-Normal Pattern of Species
Abundance In Communities
Low
◄ Abundance ►
(Log Scale)
High
Very few species have extremely
high relative abundance
Very few species have extremely
low relative abundance
Most species are moderately
abundant
Plants
Birds
Number of Species
Log-Normal Pattern of Species
Abundance In Communities
Low
◄ Abundance ►
(Log Scale)
High
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
AAAA
AAAA
AAAA
ABCD
AAAA
AAAA
AAAA
ABCD
DCBA
BCAD
CDAB
Species Diversity
AAAA
AAAA
AAAA
AAAA
Lowest
Diversity
ABCD
AAAA
AAAA
AAAA
Shannon-Weiner Index
Pages 374-375
Table 16.1
ABCD
DCBA
BCAD
CDAB
Highest
Diversity
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
Quadrupedal
Mammals
(4 legged furry things!)
75
Number
of
species
50
25
8
Muncie
40
Latitude
72
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 Stable
Less 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
European
Starling
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
Low
High
Frequency or intensity of disturbance