Extinction

1. Extinction © 2002 by Prentice Hall, Inc. Upper Saddle River, NJ 07458

2. Extinction • All individuals die without producing progeny • Pseudoextinction • Species disappear over evolutionary time • Lineage transformed into separate lineages 03

3. Fossil Record • Extinct species to living species – 1,000:1 • Average life span of a species – 4 million years • Average extinction rate – 2.5 species per year • Total number of species over time – 10 million 03

4. Biased fossil record • Favors successful, geographically wide-ranging species • Persist longer than the average • Biased toward vertebrates and mollusks 03

5. Background extinction rates are probably higher than indicated in fossil record. • Example: Extinction rates 10 times higher than predicted by fossil record 03

6. Present extinction rate much higher than in the past or predicted. • Effects due to humans – Distant Past • Correlation between human population growth and the number of extinctions 03

7. 6 5 50 4 Birds 40 Mammals Number of humans (billions) 3 Number of extinct species 30 2 20 1 10 0 0 1650 1700 1750 1800 1850 1900 1950 2000 1600-1700 1700-1800 1800-1900 1900-2000 Year Year 03

8. Effects due to humans (cont.). • Large scale extinctions in North and South America coinciding with the arrival of humans (11 thousand years ago) • North America lost 73% of its genera of large mammals • South America lost 80% of its genera of large mammals 03

9. Effects due to humans (cont.). • Large scale extinctions in Australia coinciding with the arrival of humans (13 thousand years ago) • Lost nearly all of its large mammals, giant snakes, and reptiles • Nearly half of its large flightless birds • Probable causes of these extinctions • Hunting • Some climate change 03

10. Effects due to humans – Recent Past • Devastating effects on islands • Hawaii – 4th and 5th century Polynesians arrived • Exterminated 50 out of 100 species of endemic land birds. 03

11. Devastating effects on islands (cont.) • Madagascar – last 1,500 years • Exterminated • Giant elephant bird, largest bird ever recorded • 20 species of lemur, most larger than any surviving species • 2 giant land tortoises 03

12. Devastating effects on islands (cont.) • New Zealand – End of the 18th century • Entire avian megafauna consisting of huge land birds was exterminated • Accomplished through hunting and habitat destruction 03

13. 03

14. Stop 03

15. Islands vs. continental areas • Reasons for differences in extinction rate • Island species may consist of a single population 03

16. Island species may have evolved in the absence of terrestrial predators • Characteristics contributing to extinction • Flightlessness • Tameness • Reduced reproductive rates 03

17. 100 Habitat loss Exotic species 75 Pollution Hunting 50 Percent endangered Disease 25 0 Hawaiian Birds Continental U.S. plants Hawaiian plants Continental U.S. birds

18. Introduced species effects • Competition • Not been shown to eliminate an entire species • Predation • Rats, cats, and mongooses have accounted for at least 112 of 258 extinctions of birds on islands (43%). 03

19. Disease and parasitism • Avain malaria in Hawaii accounted for the loss of 50% of the local Hawaiian bird species 03

20. Habitat destruction • A prime cause of extinction • Ex. Deforestation • Subtle alterations (e.g. pollution) have not yet been shown to cause extinction • Direct exploitation – Hunting • Caused numerous extinctions 03

21. Endangered Species • Definition – a species that is thought to be at risk of extinction in the foreseeable future. 03

22. Factors threatening species with Extinction . • Habitat loss or modification • Hunting • Accidental or deliberate introduction of exotic species • Deliberate eradication • Incidental eradication • Disease, both exotic and endemic 03

23. Characteristics of Factors • Human in origin • Species are threatened with several factors simultaneously • Relative importance as measured by frequency of occurrence 03

24. Threat and classes of threats Percent of species affected 0 10 20 30 40 50 60 Habitat loss & modification: 76% Cultivation & settlement Pastoral development Logging & plantations Other Exploitation: 50% Meat Fur and hides Live trade Introductions: 18% Predators Competitors Others Limited distribution Persecution Disturbance Incidental take Disease

25. David Wilcove categorized threats to plants and animals in the US • Five categories • Habitat destruction • Alien species • Overharvesting • Disease (both native and alien) • Pollution 03

26. Percent of species threatened 0 10 20 30 40 50 60 70 80 90 100 All species Vertebrates Invertebrates Plants Mammals Birds Reptiles Amphibians Fish Freshwater mussels Butterflies Other invertebrates Habitat loss Exotic species Pollution Over exploitation Disease

27. Percentage endangered 1 1.5 2 2.5 3 3.5 0 0.5 Mammals Fish Birds Reptiles Amphibians All invertebrates 03

28. 03

29. The majority of threatened mammals occur in tropical countries. • Bigger countries have more endangered species than smaller countries • US and endangered reptiles, amphibians, and fishes • Better monitoring and documenting activities 03

30. 60 55 Madagascar Indonesia 50 45 Brazil India 40 China Australia Number of threatened mammals 35 Tanzania Zaire 30 Peru United States Vietnam Cameroon Colombia 25 Mexico Thailand South Africa Nigeria Laos Argentina 20 10,000 20,000 50,000 100,000 500,000 1,000,000 2,000,000 200,000 Country area (1000 ha)

31. Prone to Extinction 03