1. Biodiversity and Extinction
Nothing is Forever

2. Natural Extinctions
Surprisingly enough, we know very little about natural extinctions
In the past, known only from fossil records
Physical evidence of cause rarely preserved
Cause and Effect hard to establish
Post hoc ergo propter hoc danger
Even if cause established, what’s the mechanism?

3. Natural Extinctions Habitat Disruption Habitat Modification
Volcanic Eruptions
Asteroid Impact
Habitat Modification
Climate Change
Mountain-Building
Sea Level Change
“Exotic” Species
Continental Drift

4. Things that Probably Don’t Cause Natural Extinctions
Epidemics
Rapid co-evolution of disease and host
Evolution of New Competitors in Place
Existing organisms already well-adapted

5. Human-Caused Extinction
Excessive Predation (Food, fur, collecting, pest eradication, etc.)
Habitat Destruction
Destruction of keystone species
Introduction of Exotic Species
Competitors
Predators
Diseases
Pollution and Contamination

6. There Goes the Neighborhood
Humans Show Up and Megafaunas Go Extinct
Australia 40,000 years ago
Americas 15,000 years ago
Madagascar 1000 years ago
New Zealand 1000 years ago

7. Did Humans Cause the American Mass Extinction?
Contentious: Threatens Image of Early Humans As Stewards of Environment
Immigrants From Arctic Wouldn’t Have Fine-tuned Cultural Sense of How to Manage Temperate Environment
American Fauna Not Accustomed to Humans

8. What Caused the American Mass Extinction?
Climate Change?
Rode out 20+ Previous Glacial Cycles
Change in Ecology?
C3 and C4 Grasses

9. C3 and C4 Grasses
Refers to chemical reactions during photosynthesis (3- versus 4-carbon molecules)
C3 Grasses are cool climate, C4 grasses are warm climate
C4 grasses are richer in silica particles and wear teeth faster

10. What Caused the American Mass Extinction?
Why Didn’t All Megafauna go Extinct?
Bison, Pronghorn, Deer, Grizzly Bears
Did Humans Really Hunt Megafauna?
Central Asian Mammoth-bone Huts, but Rabbits Are Main Bones in Food Dumps
What killed off Saber-Tooth Cats?
Did Humans Kill Off Some Keystone Species?
Timing is Sure Suspicious

11. Eating Our Way to Extinction
Steller’s Sea Cow
Cold-Water Relative of Manatee
Extinct 1768
Great Auk
Flightless, Penguin-like North Atlantic Bird
The Original “Penguin”
Nice Example of Convergent Evolution
Extinct 1844

12. The First High-Tech Extinction
The Passenger Pigeon
The First High-Tech Extinction

13. The Passenger Pigeon
May once have been the most numerous bird on the planet
Estimated 5 billion
Made up 30-40% of all North American birds
Flocks 1 mile wide, 300 miles long
Evolved to travel and breed en masse
Protection against most predators

14. Disloyalty

15. Humans and the Passenger Pigeon
Unlike other predators, humans exploited the mass flocks of the passenger pigeon
Netting, mass shooting
Railroads shipped pigeons to market, created demand
Declines noted by 1860
Species could probably have survived even this predation, except….

16. Extinction of the Passenger Pigeon
Pigeons were hunted in nesting sites
Hunters used telegraph to learn of colonies
Conservation laws too little, too late
Last wild pigeons shot Wisconsin, 1899 and Ohio, 1900

17. Extinction of the Passenger Pigeon
Scattered birds could not breed
Captive breeding attempts failed
Last bird died in Cincinnati Zoo, September 14, 1914, 1 PM
The only extinction we can time to the minute

18. When Your Best Just Isn’t Good Enough
The Heath Hen
When Your Best Just Isn’t Good Enough

19. The Heath Hen Eastern race of the prairie chicken
Once ranged from Maine to Virginia
Hunting caused visible decline by 1800, steep by 1830
By 1870, restricted to Martha’s Vineyard, Massachusetts
By 1906, only 50 left
1907, Sanctuary established

20. The Heath Hen – Back From the Brink?
1907: Sanctuary established for last 50 birds
By 1915, number had grown to 2000
Species had been rescued?

21. The Heath Hen – Over the Brink
: Heath hen had grown from 50 to 2000 birds
1916: Fire destroyed most of refuge
Harsh winter and influx of hawks further damaged species
Flock attacked by disease from domestic turkeys
By 1927, only 13 left, mostly male
Last bird died, 1932

22. Too Adaptable for its Own Good
Carolina Parakeet
Too Adaptable for its Own Good

23. Carolina Parakeet Only Parrot Native to U.S.
Once ranged from Virginia to Texas
Adapted readily to agriculture and became regarded as a pest
Widely hunted
Rare by 1880’s
Last Seen in Florida about 1920

24. Recovering From Near Disaster
Cheetahs once ranged worldwide
Remaining 20,000 are genetically identical
Near extinction 10,000 years ago
Generations of close inbreeding
Were able to re-occupy large range because nothing had filled ecological niche

25. When You Can’t Go Home Again
American Chestnut was once a major food crop and lumber source
Accounted for half the value of eastern timber
Devastated by blight
Isolated trees and viable roots still survive
Research on blight immunization
Even if blight cured, other trees have filled ecological niche

26. Biodiversity Scales of organization
genetic -- diversity of genetic information found within species and populations
species -- diversity of species
community -- diversity of community composition
ecosystem -- diversity of assemblages of communities (Fox River watershed)
landscape -- diversity of assemblages of ecosystems (Western Great Lakes)

27. Island Biodiversity
Single islands (mountain tops) always have fewer species than areas on the “mainland” of similar size
Because islands are isolated, it will be harder for species to immigrate to them, lowering the rate of immigration.
Because of limited resources on islands, carrying capacity will be lower, decreasing population sizes and increasing extinction rates.

28. Island Biodiversity
Theory of island biogeography has been termed the 'First Law of Conservation Biology.' 
Because of human actions, natural habitats are becoming increasingly isolated and island-like. 
By identifying potential mechanisms underlying the loss of species diversity, Island Biogeography Theory may help suggest ways in which we can design nature reserves to maximize their ability to maintain diversity.

29. Habitat Fragmentation
Biodiversity often increases when habitats are fragmented
Many species need large areas
Typically large ranges
Availability of food
Protection from predators and invaders (Example: cowbirds and songbird decline)
Corridors as solution?

30. Exotic Species Volunteers – natural chance immigrants (cattle egrets)
Unintentional (rats, English sparrows)
Escaped ornamentals (kudzu, purple loosestrife)
Escaped pets (feral cats, house finches)
Escaped domestic animals (pigs, goats)
Bio-control gone haywire (mongooses)
Most exotics not street smart
Vigorous exotics have no natural predators
Hawaii: 80% overrun by exotic species

31. Island Biodiversity and Reserves
A large reserve is better than a small reserve
A single undivided reserve is better than a number of small reserves
A few large reserves are better than a number of small reserves
Reserves should be spaced equally from another, not linearly
Linear reserves should be connected with corridors
If reserve is small and isolated, it should be circular and not linear

32. The Sixth Extinction?
Sixth Extinction by Richard Leakey and Roger Lewin 1995
Are we creating a mass extinction to rival the other major events in the geologic past?

33. Mass Extinctions

34. Mass Extinctions
The higher the taxonomic level, the lower the extinction level
Easy to wipe out a species, hard to wipe out a family
250 m.y. ago: 90% of species lost, 50% of families, some orders, no phyla

35. Why High-Order Taxa Survive

36. Lazarus Taxa
Groups that vanish during mass extinctions and then reappear
Where do they go?
Why don’t they change?

37. Extinct Species About 2100 dinosaur fossils in museums
285 genera, 336 species
May have been genera total
Compare to 1300 living mammal genera
About 30,000 marine invertebrate genera (more genera living now)

38. Diversity and the Fossil Record
Incomplete
Many organisms will never be fossilized
No hard parts
Rare or very restricted
Environments where fossilization unlikely
Often impossible to distinguish species
Have to rely on skeletons, shells, hard parts
No information on coloration
No information on internal organs

39. Fossilization Most sediment is transported by running water
Most fossils are in water-laid rocks
Bias toward aquatic organisms
Shells
Favorable setting
Terrestrial fossils preserved erratically

40. What We Wouldn’t Find in the Fossil Record
Dusky seaside sparrow (color variant only)
Ivory-Billed Woodpecker, California Condor, Steller’s Sea Cow (never abundant)
Most rain forest species (too restricted, not likely to be fossilized)

41. What We Would Find in the Fossil Record
Extinction of Pleistocene megafauna
Extinction of Passenger Pigeon
Reduction in range of bison, large carnivores
Expansion of human domestic animals
Reduction in rain forest, changes in land cover
Humans and artifacts

42. The Sixth Extinction – So Far
The biggest change so far (Pleistocene extinction) was prehistoric
Have been very significant shifts in vegetation and fauna
Not many extinctions would show up in the fossil record
Little change in easily fossilized marine faunas