I.
Biodiversity – Definitions and Assessment
• Major issue – Potential loss as a result of human activities
A.
Definitions
• Discussion requires clear consensus about what biodiversity is and how it’s defined
• Fundamental unit = species
• What is a species??
1.
Species
• Group of genetically similar organisms that interbreed naturally and freely to produce viable, fertile offspring, but do not share this behavior and outcome with individuals of other species
• Problem: Many people consider this definition to be inadequate. Why??

I.
Biodiversity – Definitions and Assessment
A.
Definitions
1.
Species a.
Asexual Reproduction/Parthenogenesis
• All prokaryotes
• Some protists, fungi, plants, animals b.
Interbreeding Naturally & Freely
• Some isolated populations could interbreed if geographic barrier could be surmounted
• Separate species? Subspecies? Populations?
c.
Natural Hybrids
• Ex – Horse + Donkey  Mule
• Ex – Queen + Blue  Townsend’s Angelfish
• Separate species? If a natural hybrid disappears, is it really gone so long as parent species remain?
d.
Polymorphism
• Ex - Hamlets
• How different must two species be to constitute separate species? Humans and chimpanzees are estimated to be 98% identical at the DNA level.

I.
Biodiversity – Definitions and Assessment
A.
Definitions
1.
Species a.
Asexual Reproduction/Parthenogenesis
• All prokaryotes
• Some protists, fungi, plants, animals b.
Interbreeding Naturally & Freely
• Some isolated populations could interbreed if geographic barrier could be surmounted
• Separate species? Subspecies? Populations?
c.
Natural Hybrids
• Ex – Horse + Donkey  Mule
• Ex – Queen + Blue  Townsend’s Angelfish
• Separate species? If a natural hybrid disappears, is it really gone so long as parent species remain?
d.
Polymorphism
• Ex - Hamlets
• How different must two species be to constitute separate species? Humans and chimpanzees are estimated to be 98% identical at the DNA level.

Blue Queen
Townsend’s

I.
Biodiversity – Definitions and Assessment
A.
Definitions
1.
Species a.
Asexual Reproduction/Parthenogenesis
• All prokaryotes
• Some protists, fungi, plants, animals b.
Geographic Isolation
•
Populations could interbreed if geographic barrier could be surmounted
•
Separate species? Subspecies? Populations?
c.
Natural Hybrids
• Ex – Horse + Donkey  Mule
•
• Ex – Queen + Blue  Townsend’s Angelfish
Separate species? If a natural hybrid disappears, is it really gone so long as parent species remain?
•
Quagga d.
Polymorphism
• Ex - Hamlets
• How different must two species be to constitute separate species? Humans and chimpanzees are estimated to be
98% identical at the DNA level.

Barred
Blue
Indigo
Black
Golden
Yellowtail

I.
Biodiversity – Definitions and Assessment
A.
Definitions
• How do we identify a species?
• How do we quantify the number of species in an area when there is disagreement about what constitutes a species?
•
Recently: Focus on preservation of processes that lead to speciation
• What processes produce and maintain species?
2.
Reproductive Isolation
• Many factors can prevent individuals from interbreeding
• Prezygotic
• Act prior to fertilization
•
Postzygotic
• Act following fertilization

Time of Day
Time of Year
Courtship
Sounds/Songs
Flowers
Fiddler Crabs
Plants
Broadcast Spawners
Bullfrog x
Leopard Frog
Horse (2n=64) x
Donkey (2n=62) 
Mule (2n=63)

I.
Biodiversity – Definitions and Assessment
A.
Definitions
3.
Components of Biodiversity
• The term “biodiversity” often is used incorrectly or incompletely
• Not synonymous with “species diversity”
• Encompasses three measures a.
Species Diversity
1) Species richness – Total number of species
• Often cited incorrectly as “biodiversity”
• Fairly simple to estimate from rarefaction curves
2) Evenness – Proportions of species in a community
• More difficult to determine (requires more complete survey) b.
Genetic Diversity – Variety of genotypes c.
Ecosystem Diversity – Variety of habitat types

I.
Biodiversity – Definitions and Assessment
A.
Definitions
3.
Components of Biodiversity
• The term “biodiversity” often is used incorrectly or incompletely
• Not synonymous with “species diversity”
• Encompasses three measures a.
Species Diversity
1) Species richness – Total number of species
• Often cited incorrectly as “biodiversity”
• Fairly simple to estimate from rarefaction curves
2) Evenness – Proportions of species in a community
• More difficult to determine (requires more complete survey) b.
Genetic Diversity – Variety of genotypes c.
Ecosystem Diversity – Variety of habitat types

I.
Biodiversity – Definitions and Assessment
B.
Estimates of Biodiversity
• Described species ~ 1.8 million
• Insects > 1,000,000 species
• Plants > 290,000 species
• Probably an underestimate
• Only ~5000 species of bacteria
• Less conspicuous species studied less often
• Estimates range from 5 – 30 million
• Average estimate ~ 17.5 million
C.
Estimates of Extinction Rates
•
Current estimates ~ 17,500 species year -1
• 1 out of every 1000 species on Earth each year
• “Background” rate from fossil record
• 1 out of every 1-10 million species on Earth each year

I.
Biodiversity – Definitions and Assessment
C.
Estimates of Extinction Rates
• Problems a.
Difficult to know when a species is extinct
• Ex – Coelacanth, ivory billed woodpecker, giant lemur b.
Extinctions may not happen immediately
• Short-lived species show effects rapidly
• Long-lived species may appear to be unaffected for long periods of time
• “Biologically extinct” – Populations not selfsustaining
• “Living dead” - Janzen c.
Uncertainty about number of species in an area
• Wilson – “No precise estimate can be made of the numbers of species being extinguished in the rain forests or in other major habitats, for the simple reason that we do not know the numbers of species originally present”

I.
Biodiversity – Definitions and Assessment
C.
Estimates of Extinction Rates
• Consideration: Wilson – Projections in tropical settings (where most of biodiversity loss currently is happening) are conservative
•
•
•
•
• Tropical species have localized distributions that make them especially vulnerable to habitat loss
• Damaging loss of genetic diversity may occur, even if outright extinction of a species doesn’t happen

II.
Biodiversity – Factors
A.
Selective Mortality
• Species-specific diseases/pests
• Ex – Dutch elm disease
• Ex – Western bark beetles
• Predation
• Ex – Birds with colorful plumage
• Ex – Sea urchins (sushi)

II.
Biodiversity – Factors
B.
Habitat Disturbance
• Non-selective habitat disturbance has potential to increase diversity
• Prevents competitive exclusion
• Intermediate disturbance  Maximum diversity

II.
Biodiversity – Factors
B.
Habitat Disturbance
• Fire and fire-dependent species
• Ex – Peter’s Mountain Mallow (Iliamna corei)
• Discovered in 1927 (50 plants)
• Endemic to meadow in western Virginia
• 1986 - Three plants remaining
• Not setting seed
• Listed as endangered
• Research on seeds indicated importance of fire
• Cracks hard seed coat, aiding germination
• Removes competing vegetation
• Had been suppressed in the area
• Controlled burns in 1992 and 1993 led to appearance of 500+ seedlings

II.
Biodiversity – Factors
C.
Habitat Fragmentation/Destruction
• Most significant factor causing species loss
• Smaller habitats support fewer species and smaller populations than large habitats
• Population sizes tend to fluctuate more in smaller habitats than large habitats
• Reduced population  Lower genetic diversity
• Behavior of territorial species changes in fragments, esp. when territory size ~ fragment size
• Fragments may not support self-sustaining populations (rely on immigration from outside)

• Mount Hood
National Forest,
Oregon
• Patches due to timber removal

II.
Biodiversity – Factors
C.
Habitat Fragmentation/Destruction
• Most significant factor causing species loss
• Smaller habitats support fewer species and smaller populations than large habitats
• Population sizes tend to fluctuate more in smaller habitats than large habitats
• Reduced population  Lower genetic diversity
• Behavior of territorial species changes in fragments, esp. when territory size ~ fragment size
• Fragments may not support self-sustaining populations (rely on immigration from outside)

II.
Biodiversity – Factors
C.
Habitat Fragmentation/Destruction
• Fragmentation increases edge effects
• Positive effects
• Increased light to plant species at edges
• Negative effects
• Increased predation by animals foraging at habitat edge
• Ex – Nesting success among migratory birds in Midwestern forests was lower in fragments due to increased nest predation and parasitism by cowbirds
• Benefit – Herbivorous insects in fragmented habitats experience less parasitism
(reduction of parasite’s habitat)

III.
Biodiversity – Value
A.
Value to Humans
•
•
Biodiversity loss could lead to removal of species that benefit humans but aren’t cultivated currently
Ex – Chapin et al. suggested increase in frequency of Lyme disease during 20 th century may have been related to increase in abundance of tick-bearing mice (once controlled by food competition with passenger pigeons)
•
•
•
•
•
•
Species extinction reduces potential pool of species containing chemical compounds with pharmaceutical or industrial applications
Counter
– Many pharmaceutical companies now use directed design to search for new drugs
Question – How do we know whether a species has value?
Problem – Benefits may not be obvious
Difficult to convince people that it’s important to preserve something with no immediately apparent intrinsic value to them
Ex – Economic value of viral resistance added to commercial strains of perennial corn through hybridization with teosinte
(Mexican wild grass) is ~ $230-300 million/year

III.
Biodiversity – Value
B.
Ecosystem Value
• Biodiversity can have large effects on ecosystem productivity and stability
1.
Benefits of biodiversity a.
Productivity
• Halving species richness reduces productivity by 10-20% (Tilman) b.
Nutrient retention
• Loss of nutrients through leaching is reduced when diversity is high
• Caveat – Studies to date have focused on low diversity communities ( Why?
); can those results be generalized?

III.
Biodiversity – Value
B.
Ecosystem Value
1.
Benefits of biodiversity
•
• c.
Ecosystem stability
Mechanism
•
Multiple species within a trophic level compete for resources
• If the abundance of one species declines due to perturbation, competing species may increase in abundance
•
Individual species abundances may vary, but community as a whole is more stable with more species
Consequences
•
• High diversity doesn’t guarantee that individual populations won’t fluctuate
Ex
– Higher diversity (unfertilized) plots of native plant species
1) Maintained more biomass during drought than lower diversity (fertilized) plots
2) Conferred greater resistance to pests and diseases
3) Showed reduced predation by herbivorous insects and reduced invasion by weeds

III.
Biodiversity – Value
B.
Ecosystem Value
2.
Considerations
• a.
Species richness vs. Species evenness
Simple species richness may be deceptive as an indicator of biodiversity and ecosystem stability
•
Evenness usually responds more rapidly to perturbation than richness and may have important ecosystem consequences
• Richness is typical focus of studies and policy decisions
•
• b.
Importance of individual species
Different species affect ecosystems in different ways (keystone species vs. non-keystone species)
•
• Ex – Sea otters/Sea urchins/Kelp forests in eastern Pacific
Ocean
Ex
– Pack ice/Krill/Salps in Southern Ocean
•
•
Question - How many species are required to maintain
“normal” ecosystem function and stability?
No magic number
Losing one ant species in a tropical forest may have less immediate impact than losing one species of fungus that is crucial to nutrient cycling in the soil

IV.
Biodiversity – Management
• Strategies outlined in Convention on Biological
Diversity
• Developed between 1988 and 1992
• Opened for ratification at UN Conference on
Environment and Development (Rio “Earth Summit”)
• Ratified by 168 nations; went into force in Dec 1992
• Objectives – “…the conservation of biological diversity, the sustainable use of its components and the fair and equitable sharing of the benefits arising out of the utilization of genetic resources…”
• Articles 8-9 specify a combination of in situ and ex situ conservation measures
• Primary use of in situ conservation
• Use of ex situ measures as a complement