03 Chapter 3 Extinction 2002 by Prentice Hall

Chapt. 03 Outline • Rate of extinction • Causes of extinction • Risks confronted by endangered species • Characteristics of species and their relationship to extinction 2

Chapt. 03 The Extinction Crisis • Extinction – All individuals die without producing progeny • Pseudoextinction – Species disappear over evolutionary time 3

Chapt. 03 The Extinction Crisis • Pseudoextinction – Lineage transformed into separate lineages • Fossil Record – Extinct species to living species – 1, 000: 1 4

Chapt. 03 Extinction Crisis (cont. ) • Fossil Record (cont. ). – Average life span of a species – 4 million years – Average extinction rate – 2. 5 species per year 5

Chapt. 03 Extinction Crisis • Fossil Record – Total number of species over time – 10 million • Biased fossil record – Favors successful, geographically wide-ranging species – Persist longer than the average 6

Chapt. 03 Extinction Crisis • Biased fossil record (cont. ) – Biased toward vertebrates and mollusks – Background extinction rates are probably higher than indicated in fossil record. • Example Extinction rates 10 times higher than predicted by fossil record 7

Chapt. 03 Extinction Crisis – Background extinction rates are probably higher than indicated in fossil record (cont. ). • 1 every 50 years for birds living today 8

Chapt. 03 9 Extintion Crisis • Present extinction rate much high than in the past or predicted. – Effects due to humans – Distant Past • Correlation between human population growth and the number of extinctions (Figure 3. 1)

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

Chapt. 03 Extinction Crisis • 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 11

Chapt. 03 Extinction Crisis • Effects due to humans (cont. ). – Large scale extinctions in North and South America (cont. ). • South America lost 80% of its genera of large mammals 12

Chapt. 03 Extinction Crisis (cont. ) • 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 13

Chapt. 03 Extinction Crisis (cont. ) – Probable causes of these extinctions • Hunting • Some climate change 14

Chapt. 03 15 Extinction Crisis • Effects due to humans – Recent Past – Devastating effects on islands • Hawaii – 4 th and 5 th century Polynesians arrived – Exterminated 50 out of 100 species of endemic land birds.

Chapt. 03 16 Extinction Crisis – Devastating effects on islands (cont. ) • New Zealand – End of the 18 th century – Entire avian megafauna consisting of huge land birds was exterminated – Accomplished through hunting and habitat destruction

Chapt. 03 17 Extinction Crisis – 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

Chapt. 03 Patterns of Extinction • Islands vs. continental areas (Table 3. 1) 18

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Chapt. 03 20 Patterns of Extinction – Reasons for differences in extinction rate • Island species may consist of a single population – Single climatic event can lead to extinction

Chapt. 03 21 Patterns of Extinction – Reasons for differences in extinction rate (cont. ) • Island species may have evolved in the absence of terrestrial predators – Characteristics contributing to extinction » Flightlessness » Tameness » Reduced reproductive rates – Ex. Hawaii (Figure 3. 2)

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

Chapt. 03 Patterns of Extinction • Causes of extinction (Figure 3. 3) 23

Chapt. 03 24 No cause assigned 56% Introduced animals 17% Habitat destruction 16% Hunting Other causes 10% 1%

Chapt. 03 25 Patterns of Extinction – 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%).

Chapt. 03 Patterns of Extinction • Introduced species effects (cont. ) – Disease and parasitism • Avain malaria in Hawaii accounted for the loss of 50% of the local Hawaiian bird species 26

Chapt. 03 27 Patterns of Extinction – Causes of Extinction (Cont. ) • 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 – Ex. Figure 3. 4

Chapt. 03 Endangered Species • Definition – a species that is thought to be at risk of extinction in the foreseeable future. • Factors threatening species with Extinction – Habitat loss or modification 28

Chapt. 03 Endangered Species • Factors threatening species with Extinction (cont. ). – Hunting – Accidental or deliberate introduction of exotic species – Deliberate eradication 29

Chapt. 03 Endangered Species • Factors threatening species with Extinction (cont. ). – Incidental – Disease, both exotic and endemic 30

Chapt. 03 Endangered Species • Characteristics of Factors – Human in origin – Species are threatened with several factors simultaneously – Relative importance as measured by frequency of occurrence 31

Chapt. 03 Endangered Species • Characteristics of Factors (cont. ) – Ex. Threats facing terrestrial mammals in Australia and the Americas • • 119 species considered endangered 75% threatened by more than one factor 27 species face four or more threats Major threat – 76% of the species are experiencing habitat loss or modification • Figure 3. 5 32

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

Chapt. 03 Endangered Species • Significance of hunting – Valuable fur and wood (Figure 3. 6) • Overexploitation – Overharvesting for commercial interests 34

Chapt. 03 Endangered Species • Overexploitation (cont. ). 1998, – Rare plants are threatened by collectors • David Wilcove categorized threats to plants and animals in the US – Five categories 35

Chapt. 03 Endangered Species – Five categories (cont. ) • Habitat destruction • Alien species • Overharvesting • Disease (both native and alien) • Pollution 36

Chapt. 03 Endangered Species – Sample size: 1880 species – Results (Figure 3. 7) 37

0 10 Percent of species threatened 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

Chapt. 03 Endangered Species • Categorization of threats by class of species (Figure 3. 8) 39

Chapt. 03 40 Percentage endangered 0 Mammals Fish Birds Reptiles Amphibians All invertebrates 0. 5 1 1. 5 2 2. 5 3 3. 5

Chapt. 03 Endangered Species • Categorization of threats by geographic areas (Table 3. 2) 41

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Chapt. 03 Endangered Species – The majority of threatened mammals occur in tropical countries • Tropical countries have more species (therefore should have more endangered species • Tropical countries have a higher percentage of endangered species as well. 43

Chapt. 03 Endangered Species (cont. ) – Bigger countries have more endangered species than smaller countries (Figure 3. 9) 44

Number of threatened mammals Chapt. 03 45 60 55 50 Madagascar Indonesia 45 India 40 Australia 35 30 Brazil Tanzania Vietnam 25 Laos Cameroon Peru China Zaire United States Colombia Mexico Thailand Nigeria South Africa Argentina 20 10, 000 20, 000 50, 000 100, 000 200, 000 Country area (1000 ha) 500, 000 1, 000 2, 000

Chapt. 03 Endangered Species (cont. ) – US and endangered reptiles, amphibians, and fishes • Better monitoring and documenting activities 46

Chapt. 03 Endangered Species • Correlations between human factors and extinction – 1995, Kerr and Currie Compared 90 countries – Six indices of human activities (Table 3. 3) 47

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Chapt. 03 Endangered Species (cont. ) • Correlation between human factors and extinction (cont. ) • Human population explained the most variation in the proportion of endangered species of birds. • Per capita GNP explained the most variation in mammals 49

Chapt. 03 Species Characteristics and Extinction • Rarity (Fig. 3. 10) – Determined by • Geographic range, • Breadth of habitat • Local population size • Ability to disperse (Fig. 3. 10) 50

Chapt. 03 Species Characteristics and Extinction (cont. ) – Rescuing a population through immigration • Degree of specialization (Fig. 3. 10) 51

Chapt. 03 Species Characteristics and Extinction (cont. ) • Degree of specialization (cont. ) – Organisms that are specialized are more likely to become extinct • Limited food • Limited habitat 52

Less prone to extinction More prone to extinction Common 1) Rarity Rare N 2) Dispersal ability N t Poor dispersal Habitat destroyed Not able to reach new fragment Habitat fragments 3) Degree of specialization. High specialization t Good dispersal Habitat destroyed Can reach new fragment Habitat fragments Low specialization

Chapt. 03 Species Characteristics and Extinction (cont. ) • Population variability (Fig. 3. 10) – Stable populations are less likely to go extinct • Trophic status (Fig. 3. 10) – Applies to animals only – Higher trophic levels more at risk 54

Chapt. 03 55 More prone to extinction Less prone to extinction 4) Population variability Low variability High variability N 5) Trophic status Population size relatively constant: extinction unlikely Sudden population decline can lead to extinction N t t High trophic status Pyramid of numbers Low trophic status Top carnivores are very few, so prone to extinction as Carnivores - tens Herbivores - hundreds Plants - thousands

Chapt. 03 Species Characteristics and extinction (cont. ) • Life span (Fig. 3. 10) • Reproductive ability (Fig. 3. 10) 56

Chapt. 03 57 More prone to extinction 6) Life span Short life span Less prone to extinction Long life span 7) Reproductive ability High reproductive ability Low reproductive ability

Chapt. 03 Summary • Important causes of extinction – Introduced species (39%) – Habitat destruction (36%) – Direct exploitation (23%) 58

Chapt. 03 Summary (cont. ) • Factors threatening species – Habitat destruction • Deforestation and ecosystem conversion 59

Chapt. 03 Summary (cont. ) • Species characteristics affecting the sensitivity to extinction – – Rarity Ability to Disperse Degree of Specialization Population variability 60

Chapt. 03 Summary • Species characteristics affecting the sensitivity to extinction (cont. ) – Trophic Status – Longevity – Reproductive ability 61

Chapt. 03 Discussion Question #1 • Which type of organisms do you think deserve priority in conservation efforts and why? 62

Chapt. 03 Discussion Question #2 • What ecological information would you need in order to list a species as endangered? 63

Chapt. 03 Discussion Question #3 • If we are concerned with protecting rare species, should we also be concerned with protecting subspecies (or races) or even individual populations? Discuss the pros and cons of this issue. 64