I. Biodiversity – Factors

E. Exotic Species2. 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. suggest increased frequency of Lyme disease in 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

II. Biodiversity – Value

A. Value to Humans

• 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 productivity1. 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 Value1. Benefits of biodiversity

c. Ecosystem stability• Mechanism

• Multiple species 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 Value2. 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 decisionsb. 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. Purposes1. 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

IV. Genetic Engineering

C. Advantages1. Greater agricultural yields

• More food production per acre could• Reduce area needed to support existing population• Support future population growth

• Ex – European corn borer destroys 7% of annual corn harvest worldwide• Modified corn resistant to ECB could eliminate this loss• Extra corn = 7-10 mmt (enough to feed 60 million people)

2. Reduced herbicide use• Wheat, corn, soybeans, cotton, sugar beets, alfalfa, etc. engineered to be

resistant to certain herbicides (e.g. Roundup)• Farmers can spray crops with less herbicide to kill weeds• Ex – Soybeans – Reduction of herbicide use by 10-40% from 1996-1997

3. Reduced pesticide use• Crop plants can be engineered for resistance to certain pesticides• Ex – Insect resistant cotton planted in Alabama led to an 80% reduction

in use of insecticides on cotton from 1996-19974. Environmentally beneficial tasks

• Ex – Bacteria engineered to degrade petroleum rapidly can be used to clean up oil spills

5. Novel properties• Ex – Phytase maize (approved in China, 2009)

• Enzyme makes phosphorus more available to livestock• Enhances animal growth, reduces P content of waste (up to 60%)