Biodiversity

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• Biodiversity Definitions and Assessment
• Major issue Potential loss as a result of human
  activities
• Definitions
• Discussion requires clear consensus about what
  biodiversity is and how its defined
• Fundamental unit species
• What is a species??
• 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??

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• Biodiversity Definitions and Assessment
• Definitions
• Species
• Asexual Reproduction/Parthenogenesis
• All prokaryotes
• Some protists, fungi, plants, animals
• Interbreeding Naturally Freely
• Some isolated populations could interbreed if
  geographic barrier could be surmounted
• Separate species? Subspecies? Populations?
• Natural Hybrids
• Ex Horse Donkey ? Mule
• Ex Queen Blue ? Townsends Angelfish
• Separate species? If a natural hybrid
  disappears, is it really gone so long as parent
  species remain?
• 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.

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• Biodiversity Definitions and Assessment
• Definitions
• Species
• Asexual Reproduction/Parthenogenesis
• All prokaryotes
• Some protists, fungi, plants, animals
• Interbreeding Naturally Freely
• Some isolated populations could interbreed if
  geographic barrier could be surmounted
• Separate species? Subspecies? Populations?
• Natural Hybrids
• Ex Horse Donkey ? Mule
• Ex Queen Blue ? Townsends Angelfish
• Separate species? If a natural hybrid
  disappears, is it really gone so long as parent
  species remain?
• 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.

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Blue
Queen
Townsends
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• Biodiversity Definitions and Assessment
• Definitions
• Species
• Asexual Reproduction/Parthenogenesis
• All prokaryotes
• Some protists, fungi, plants, animals
• Geographic Isolation
• Populations could interbreed if geographic
  barrier could be surmounted
• Separate species? Subspecies? Populations?
• Natural Hybrids
• Ex Horse Donkey ? Mule
• Ex Queen Blue ? Townsends Angelfish
• Separate species? If a natural hybrid
  disappears, is it really gone so long as parent
  species remain?
• Quagga
• 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.

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Barred
Black
Golden
Blue
Indigo
Yellowtail
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• Biodiversity Definitions and Assessment
• 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?
• Reproductive Isolation
• Many factors can prevent individuals from
  interbreeding
• Prezygotic
• Act prior to fertilization
• Postzygotic
• Act following fertilization

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Time of Day Time of Year
Courtship Sounds/Songs
Flowers Fiddler Crabs
Plants Broadcast Spawners
Bullfrog x Leopard Frog
Horse (2n64) x Donkey (2n62) ? Mule (2n63)
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• Biodiversity Definitions and Assessment
• Definitions
• Components of Biodiversity
• The term biodiversity often is used incorrectly
  or incompletely
• Not synonymous with species diversity
• Encompasses three measures
• Species Diversity
• Species richness Total number of species
• Often cited incorrectly as biodiversity
• Fairly simple to estimate from rarefaction curves
• Evenness Proportions of species in a community
• More difficult to determine (requires more
  complete survey)
• Genetic Diversity Variety of genotypes
• Ecosystem Diversity Variety of habitat types

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

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• Biodiversity Definitions and Assessment
• Estimates of Biodiversity
• Described species 1.8 million
• Insects gt 1,000,000 species
• Plants gt 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
• 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

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• Biodiversity Definitions and Assessment
• Estimates of Extinction Rates
• Problems
• Difficult to know when a species is extinct
• Ex Coelacanth, ivory billed woodpecker, giant
  lemur
• 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
  self-sustaining
• Living dead - Janzen
• 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

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• Biodiversity Definitions and Assessment
• 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 doesnt
  happen

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

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• Biodiversity Factors
• Habitat Disturbance
• Non-selective habitat disturbance has potential
  to increase diversity
• Prevents competitive exclusion
• Intermediate disturbance ? Maximum diversity

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• Biodiversity Factors
• Habitat Disturbance
• Fire and fire-dependent species
• Ex Peters 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

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• Biodiversity Factors
• 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)

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

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• Biodiversity Factors
• 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)

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• Biodiversity Factors
• 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
  parasites habitat)

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• Biodiversity Value
• Value to Humans
• Biodiversity loss could lead to removal of
  species that benefit humans but arent cultivated
  currently
• Ex Chapin et al. suggested increase in
  frequency of Lyme disease during 20th 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 its 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

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• Biodiversity Value
• Ecosystem Value
• Biodiversity can have large effects on ecosystem
  productivity and stability
• Benefits of biodiversity
• Productivity
• Halving species richness reduces productivity by
  10-20 (Tilman)
• 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?

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• Biodiversity Value
• Ecosystem Value
• Benefits of biodiversity
• 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 doesnt guarantee that individual
  populations wont fluctuate
• Ex Higher diversity (unfertilized) plots of
  native plant species
• Maintained more biomass during drought than lower
  diversity (fertilized) plots
• Conferred greater resistance to pests and
  diseases
• Showed reduced predation by herbivorous insects
  and reduced invasion by weeds

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• Biodiversity Value
• Ecosystem Value
• Considerations
• 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
• 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

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• 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