I.
Biodiversity
–
Factors
E.
Exotic Species
•
Species invasions may profoundly affect
ecosystems
•
Detrimental exotic species usually are
•
Superior competitors
•
Ex
–
Argentine ants, starlings, zebra mussels
•
Effective predators
•
Ex
–
Nile perch, mongeese
I.
Biodiversity
–
Factors
E.
Exotic Species
1.
Zebra mussel
•
Competitor in Great Lakes and elsewhere
•
Transported from Europe in ballast water
•
Fouling organism
•
Restricts movement of water through intake
pipes
•
Colonizes boat hulls, pier pilings, buoys, etc.
•
Fouls other organisms (clams, mussels)
•
Filter feeder
–
removes larvae and particulate
material
•
Outcompetes native shellfish species for food
and space
•
Removes larvae from water
I.
Biodiversity
–
Factors
E.
Exotic Species
2.
Mongoose
•
Predator in Hawaii
•
Introduced in 1883 to combat rat population
•
Prey on native birds
3.
Lionfish
•
Venomous predator
•
Introduced in Caribbean/W Atlantic
ca.
early/mid
1990’s
•
Preys on 65+ spp. of fishes
•
No natural predators
Nile perch
–
Lake Victoria
Brown tree snake
-
Guam
Argentine ants
-
California
Caulerpa taxifolia
-
California
II.
Biodiversity
–
Value
A.
Value to Humans
•
Economic
•
Ex
–
Lomborg: $3
-
33 trillion annually
•
Biodiversity loss could lead to
removal of species
that benefit
humans but aren’t currently known to do so
•
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
•
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 (
charisma?
)
•
Ex
–
Economic value of viral resistance added to commercial strains of
perennial corn through hybridization with teosinte (Mexican wild grass)
is ~ $230
-
300 million
•
Ex
–
Weedy tomatoes from Peru
•
Discovered in 1962 during search for potatoes
•
Seeds sent to researcher at UC Davis who used plants to breed with
other tomatoes
•
In 1980 after nearly 10 generations of crossing and backcrossing, new
strains were produced with larger fruit, improved pigmentation and
increased concentrations of sugars and soluble solids
II.
Biodiversity
–
Value
B.
Ecosystem Value
•
Biodiversity can have large effects on ecosystem
stability and productivity
1.
Benefits of biodiversity
a.
Productivity
•
Halving species richness reduces productivity by
10
-
20% (Tilman)
•
Average plot with one plant species is less than half
as productive as a plot with 24
-
32 species
•
Question
–
Can these results be extrapolated to
other systems and time/space scales?
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?
II.
Biodiversity
–
Value
B.
Ecosystem Value
1.
Benefits of biodiversity
c.
Ecosystem stability
•
Mechanism
•
Multiple species within a trophic level compete for
resources
•
If 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 maintained more biomass during drought than
lower diversity (fertilized) plots
•
High diversity may confer greater resistance to pests and
diseases
•
Ex
–
Higher diversity plots of native plant species had
greater resistance to fungal diseases, reduced predation
by herbivorous insects and reduced invasion by weeds
II.
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
•
Charismatic megafauna:
What about non
-
charismatic 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
•
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
III.
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
IV.
Genetic Engineering
A.
Background
•
Concept based on idea that organisms share
same basic genetic material (DNA)
•
Functionally similar units (genes)
•
Same basic mechanisms of
gene expression
•
Theoretically possible to transfer genes
between organisms and expect traits to be
transferred faithfully
•
Insertion of a foreign gene into a species’
genome creates a
transgenic
organism
•
Inserted gene may or may not be expressed
•
Theoretically, no limits on what can be inserted
•
Ex
–
Insulin gene inserted into bacteria
•
Ex
–
UCSD researchers inserted bacterial
luciferin/luciferase genes into tobacco plant
•
Technology offers potential to create novel
organisms with unusual and potentially
beneficial attributes
IV.
Genetic Engineering
A.
Background
•
Concept based on idea that organisms share
same basic genetic material (DNA)
•
Functionally similar units (genes)
•
Same basic mechanisms of
gene expression
•
Theoretically possible to transfer genes
between organisms and expect traits to be
transferred faithfully
•
Insertion of a foreign gene into a species’
genome creates a
transgenic
organism
•
Inserted gene may or may not be expressed
•
Theoretically, no limits on what can be inserted
•
Ex
–
Insulin gene inserted into bacteria
•
Ex
–
UCSD researchers inserted bacterial
luciferin/luciferase genes into tobacco plant
•
Technology offers potential to create novel
organisms with unusual and potentially
beneficial attributes
IV.
Genetic Engineering
B.
Purposes
1.
Accelerate and refine selection process
•
“Normal” hybridizing limited by
•
Generation time
•
Combining entire genomes, not just traits of interest
2.
Create otherwise unattainable hybrids
•
Ex
–
Arctic flounder and strawberry or tomato
•
Bottom line
-
Genetic engineering of organisms is
intended to benefit humans, not modified organisms
•
Proponents stress
potential benefits
to
humankind and the environment
•
Opponents emphasize
potential risks
and
concerns
•
Conversation with Hugh Grant
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