Biodiversity – Factors Exotic Species Species invasions may profoundly affect ecosystems

1. Biodiversity – Factors • 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

2. Biodiversity – Factors • Exotic Species • 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

4. Biodiversity – Factors • Exotic Species • Mongoose • Predator in Hawaii • Introduced in 1883 to combat rat population • Prey on native birds • Lionfish • Venomous predator • Introduced in Caribbean/W Atlantic ca. early/mid 1990’s • Preys on 65+ spp. of fishes • No natural predators

5. Nile perch – Lake Victoria Brown tree snake - Guam Argentine ants - California Caulerpa taxifolia - California

6. Biodiversity – Value • 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 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 • 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

7. Biodiversity – Value • Ecosystem Value • Biodiversity can have large effects on ecosystem stability and productivity • Benefits of biodiversity • 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? • 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?

8. Biodiversity – Value • Ecosystem Value • Benefits of biodiversity • 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

9. 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 • 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

10. 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

11. Genetic Engineering • 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

13. Genetic Engineering • 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

14. Genetic Engineering • Purposes • Accelerate and refine selection process • “Normal” hybridizing limited by • Generation time • Combining entire genomes, not just traits of interest • 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