1. I. I.Biodiversity – Definitions and Assessment B. 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 Around 300 new species described each day Average estimate ~ 17.5 million Splitting of taxa more common than lumping Tendency to increase number of described species Cryptic species

2. I. I.Biodiversity – Definitions and Assessment C. C.Estimates of Extinction Rates Geological history Periods of extinction followed by periods of rapid speciation (every ~ 26 million years) How do we estimate rates of extinction?? 1. 1.Problems a. a.Difficult to know when a species is extinct Ex – Coelacanth, ivory billed woodpecker, giant lemur b. b.Species distributed unevenly (patchy distribution) Species affected unevenly by habitat loss c. c.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 d. d.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”

3. I. I.Biodiversity – Definitions and Assessment C. C.Estimates of Extinction Rates 2. 2.Estimation Methods Area-species relationship (MacArthur & Wilson) a. a.Estimate biodiversity for a small area b. b.Extrapolate estimate to area of habitat Species ~ Area 0.25 (0.15-0.35) Increase area 10X  Increase species 2X c. c.Estimate rate at which ecosystem area is being reduced d. d.Calculate extinction rate based on predicted reduction in species richness from reduction in habitat area Current estimate ~ 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

5. I. I.Biodiversity – Definitions and Assessment C. C.Estimates of Extinction Rates 2. 2.Estimation Methods Area-species relationship (MacArthur & Wilson) a. a.Estimate biodiversity for a small area b. b.Extrapolate estimate to area of habitat Species ~ Area 0.25 (0.15-0.35) Increase area 10X  Increase species 2X c. c.Estimate rate at which ecosystem area is being reduced d. d.Calculate extinction rate based on predicted reduction in species richness from reduction in habitat area Current estimates ~ 17,500 species year -1 1 out of every 1000 species on Earth each year Myers – 40,000 year -1 Lomborg – 1033 documented from 1600 – 1998 The Skeptical Environmentalist “Background” rate from fossil record 1 out of every 1-10 million species year -1

6. I. I.Biodiversity – Definitions and Assessment C. C.Estimates of Extinction Rates Point: Estimates may be unreliable and thus invalid No action should be taken until biodiversity loss is demonstrated and shown to be harmful Counterpoint: Wilson – Projections using area- species relationships 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

7. I. I.Biodiversity – Definitions and Assessment D. D.Biodiversity Hotspots Myers – Up to 20% of the world’s plant species and more than 20% of the animal species are confined to 0.5% of the land surface Biodiversity Hotspot – Area with high degree of Biodiversity Endemism Risk of habitat degradation/loss Concept originally intended for tropical and subtropical areas Endemism less prevalent in temperate and polar regions

8. II. II.Biodiversity – Factors A. A.Nutrient Availability 1. 1.Oligotrophic Dominated by a few species able to survive on limited nutrients Low diversity, Low biomass 2. 2.Mesotrophic Support greater numbers of species Rapid colonizers held in check by nutrient limitation Less aggressive species capable of surviving High diversity, Medium biomass 3. 3.Eutrophic Dominated by a few species able to grow and/or colonize rapidly with abundant nutrients Low diversity, High biomass

9. II. II.Biodiversity – Factors B. B.Selective Colonization/Mortality 1. 1.Colonization Excellent colonizers (r-selected) may dominate newly available habitats 2. 2.Mortality Predation Ex – Birds with colorful plumage Ex – Sea urchins (sushi) Species-specific diseases/pests Ex – Dutch elm disease Ex – Western bark beetles

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

11. II. II.Biodiversity – Factors C. C.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

12. II. II.Biodiversity – Factors D. D.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)

13. Mount Hood National Forest, Oregon Patches due to timber removal

14. II. II.Biodiversity – Factors D. D.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)

15. II. II.Biodiversity – Factors D. D.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 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)

16. II. II.Biodiversity – Factors E. 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